LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class HAND-BOOK TOR HEATING AND VENTILATING ENGINEERS BY s D. HOPPAXAN. n. E. Professor of Engineering Design Purdue University ASSISTED BY BENcJA/niN P. RABER, B.S.. A\.E, Instructor In Engineering Design Purdue University LAPAYETTE, INDIANA ^ , v r> \c COPYRIGHT 1910 BY JAMES D. HOFFMAN dr\Sr ^ /^ Of THE 1 I UNIVERSITY J Vfi PREFACE In the development of Heating and Ventilating work, it is highly desirable that those engaged in the design and the installation of the apparatus be provided with a hand-book convenient for pocket use. Such a treatise should cover the entire field of heating and ventilation in a simplified form and should contain such tables as are commonly used in every day practice. This book aims to fulfill such a need and is Intended to supplement other more specialized works. These contents have been compiled, in most part, from lectures given to the Senior Mechanical Engineering class at Purdue University during the past eight years. Most of this material was issued in pamphlet form and used as a text during the year 1909-10, with very satisfactory results. It was thus possible to criticise and remove errors that would otherwise have appeared in the finished book. Because of the scope of the work, its various phases could not be dis- cussed exhaustively, but it is believed that all the fundamen- tal principles. are stated and applied in such a way as to be easily understood. It is suggestive rather than digestive. The principles presented are the same as those that have been stated many times before, but the arrangement of the work, the application and the designs are all original. Many for- mulas and rules are necessarily given; but it will be seen that, in most cases, they are developments from a few general formulas, all of which can be readily understood and remem- bered. Practical points in constructive design have also been considered. However, since the principles of heating and ventilation are founded upon fundamental thermodynamic laws, it seems best to accentuate the theoretical side of the work in the belief that if this is well understood, practical points of experience will easily follow. Chapter 16 gives a 10 suggested arrangement for a course of instruction that may be used in technical schools. It is hoped that the material here given will be simple enough for the beginner and, at the same time, sufficiently complete and exact for the engineer with years of experience. If it merits the approval of the reader, or if any part is de- fective or misleading, we trust that statements of approval or criticism, as the case may be, will be freely contributed. The only way to perfect such a book is to have the good wishes and the co-operation of engineers in all branches of the work. These are solicited. All the standard works upon the subject have been freely consulted and used. In most cases where extracts are made, acknowledgment is given in the text. In addition to this, ref- erences for continued reading are quoted at the close of each important topic. Because of these references throughout the book, we do not here repeat the names of their authors. We wish, however, to express our sincere appreciation of their valuable assitance. LaFayette, Indiana. J, D. H. September 1, 1910. B. F. R. CONTENTS CHAPTER I. (Heat) Arts. Pages 1- 4 Introductory. Measurement of Heat and Temperatures 7- 11 5 Radiation, Conduction, Convection 12- 13 CHAPTER II. (Air) 6- 9 Composition of Air. Amount Required per Person 14- 21 10- 13 Humidity 22- 27 14- 15 Convection of Air. Measurement of Air Ve- locities 28- 31 16- 20 Air Used in Combustion. Chimneys 32- 33 References on Ventilation 34 CHAPTER III. (Heat Losses) 21- 29 Heat Losses from Buildings 35- 41 30 Temperatures to be Considered 41 31 Heat given off from Lights and Persons 43 References on Heat Losses from Buildings.. 44 CHAPTER IV. (Furnace Heating) 32- 34 Essentials of the B urnace System 45- 46 35- 37 Air Circulation in Furnace Heating 47- 49 38- 47 Calculations in Furnace Design 49- 51 48 Application to a Ten Room Residence 55- 59 CHAPTER V. (Furnace Heating, Continued) 49- 51 Selecting, Locating and Setting the Furnace. 60- 64 52- 57 Air Ducts. Circulation of Air in Rooms 64- 69 58 Fan-Furnace Heating 70 59 Suggestions for Operating Furnaces 70- 71 References on Furnace Heating 72 CHAPTER VI. (Hot Water and Steam Heating) 60- 65 Comparison and Classification of Systems.. 73- 78 66- 67 Vacuum Systems for Steam 79- 81 CHAPTER VII. (Ht. Water and St. Heating, Cont'd) 68- 73 Classification and Efficiencies of Radiators.. 82- 86 74- 77 Heaters and Boilers. Combination Systems. Fittings 87- 92 CHAPTER VIII. (Ht. Water and St. Heating, Cont'd) 78- 80 Calculation of Radiator Surface 93- 99 81- 84 Pipe Sizes. Grate Area. Piping Connections. 99-102 85 General Application to Hot Water Design. .103-108 86- 87 Insulating Steam Pipes. Water Hammer 109-110 88 Feeding Return Water to Boiler 110-114 89 Suggestions for Operating Boilers 114-115 References on Hot Water and Steam Heating. 116 CHAPTER IX. (Mechanical Warm Air Heating) 90- 96 General Discussion. Blowers and Pans. Heating Surfaces J.17-129 97- 99 Single and Double Duct Systems. Air Wash- ing '. 129-132 CHAPTER X. (Mech. Warm Air Heating, Cont'd) 100-104 Heat Loss. Air Required. Air Temper- atures 133-135 105-106 Air Velocities. Area of Ducts 136-137 107-112 Heating Surface in Coils. Arrangement of Coils 137-146 113-114 Amount of Steam Used in the System 146-147 CHAPTER XI. (Mecii. Warm Air Heating, Cont'd) 115-121 Air Velocity and Pressure. Horse Power in Moving Air 148-156 122-124 Fan Drives. Speeds. Size of Engine. Piping Connections 157-162 126 General Application to Plenum System 163-167 References on Mechanical Warm Air Heat- ing 168 CHAPTER XII. (Mechanical Vacuum Heating) 127-131 General. Webster, Van Auken, Automatic and Paul Systems 169-179 References on Mechanical Vacuum Heating. 180 CHAPTER XIII. (District Heating) 132-136 General. Conduits. Expansion Joints. Anchors 181-192 137-139 Typical Design. Heat in Exhaust Steam. .193-199 140-143 Hot Water Systems. General Discussion. .. .200-202 144-146 Pressure and Velocity of Water in Mains. . .203-207 147-148 Radiation Heated by Exhaust Steam 207-208 149-157 Reheater Calculations 209-216 158-161 Circulating Pumps. Boiler Feed Pumps. .. .217-223 162-166 Radiation Supplied by Boilers and Economiz- ers 223-227 167 Total Capacity of Boiler Plant 227-230 168-170 Cost of Heating from Central Station 230-235 171 Steam System. General Discussion 236-237 172-174 Pipe Sizes. Dripping the Mains 237-239 175 General Application of Steam System to Dis- trict 239-241 References on District Heating 242 CHAPTER XIV. (Temperature Control) 176-179 General. Johnson, Powers and National Sys- tems 243-252 CHAPTER XV. (Electrical Heating) 180-182 Discussion and Calculations 253-255 CHAPTER XVI. (Course of Instruction) 183-186 Outlines for Five Designs 256-262 CHAPTER XVII. (Specifications) 187 Suggestions on Planning Specifications 263-269 APPENDIX Tables and Diagrams 271-315 CHAPTER I. HEAT ITS NATURE, GENERATION, USE, MEASUREMENT AND TRANSMISSION. 1. Introductory: In all localities where the atmosphere drops in temperature much below 60 degrees Fahrenheit, there is created a demand for the artificial heating of build- ings. As the buildings have grown in size and complexity of construction, so also this demand has grown in extent and preciseness, with the general result that from the antiquated open fire-place and iron stove, there has developed a science growing richer each day from inventive genius and manufacturing technique the science of the Heating and Ventilating- of Buildings. The purpose of this hand book shall be to outline, concisely, the fundamental princi- ples and practical applications of this science in its various branches. To the heating engineer of today, it may be that the exact nature of heat itself is perhaps of less moment than its generation and transmission, but this much should be impressed, that heat is one form of energy, that it cannot be created except by conversion from some other form, and that it is infallibly obedient to certain physical laws and principles. In generating heat today for heating purposes, the almost universal method is combustion. The union of such substances as coal, wood or peat with the oxygen of the air is always attended by a liberation of heat derived from the chemical action of the combination; and this heat is carried by some common carrier, such as air, water or steam, to the building or room to be heated where it is given off by the natural cooling process. In some instances this heat is converted into electrical energy, which is car- ried by wire to the place of use and given off by passing through a set of resistance coils, which convert it into heat; but this method is not much favored because of its inef- ficiency and the resulting expense. This latter objection 8 HEATING AND VENTILATION would not hold in the case of water power installation, where the combustion of fuel is entirely eliminated. 2. 3Ieasurement of Heat: In the measurement of heat, the most commonly accepted unit in practical engineering work is the British thermal unit, commonly abbreviated B. t. u., which may be defined as that amount of heat which will raise the temperature of one pound of pure water one de- gree Fahrenheit, at or near the temperature of maximum density, 39.1 F. This unit, the B. t. u., measures quantity of heat, while the temperature measures the degree of heat. In equal masses of the same substance the two are pro- portional. The Fahrenheit is the more commonly used tem- perature scale, especially in steam engineering. The unit of this scale is derived by dividing the distance on the thermometer between the freezing point and the boiling point of water into 180 equal degrees, the freezing point be- ing marked 32, and the boiling point 212. All temperatures in this work will be taken according to the Fahrenheit scale, and all quantities of heat expressed in British thermal units. There is a second unit of quantity of heat considerably used, especially in scientific research, known as the calorie, commonly abbreviated cal., and defined as that amount of heat which will raise one kilogram of pure water one de- gree Centigrade, at or near the temperature of maximum density, 4 C. This Centigrade is a second temperature scale, the unit of which is derived by dividing the distance on the thermometer between the freezing point and the boiling point of water into 100 equal degrees, the freezing point being marked 0, and the boiling point 100. It is often found desirable to change the expression for temperature or for quantity of heat from one system of terms to that of the other. For this purpose the following formulas will be found useful: F=%C + S2 and C = ( .F-32) (1) where F = Fahrenheit degrees and = Centigrade degrees. From these equations it may be seen that the two scales co- incide at but one point, 40 degrees. For conversion of the quantity units the following may be used: 1 British thermal unit = 0.252 Calorie. 1 Calorie = 3.968 British thermal units. MEASUREMENT OF TEMPERATURE These are for the absolute conversion of a certain quantity of heat from one system to the other. If, however, the effect of this heat is considered upon a given weight of substance and the weight also is expressed in the respec- tive systems, the following values hold: 1 Calorie per kilogram = 1.8 British thermal units per pound. 1 British thermal unit per pound = 0.555 Calorie per kilo- gram. For Conversion tables from kilograms to pounds and vice versa, see Suplee's Mechanical Engineering Reference Book, page 72, or Kent's Mechanical Engineers Pocket Book, page 22. 3. 3Ieasurement of High Temperatures: For the meas- urement of temperatures up to the boiling point of mer- Fix. 1. d. 10 HEATING AND VENTILATION cury, or approximately 600 P., the mercurial thermometer of proper range may be employed. It is more common, however, to use some form of pyrometer for temperatures above 500 P., as when the temperatures of stack gases or of fire box gases are desired. Pyrometers are built upon many different principles, the graphite expansion stem type, shown in Fig. 1, a; the thermo-electric type, shown in Fig. 1, b; or the Siemens water calorimeter type, shown in F ig. 1, c. Various other methods might be mentioned, one of the best being temperature determination by the Seger cones, which, due to varying compositions, melt at different temperatures. A line of these numbered cones is exposed to the sweep of the gases to be measured, and their temperature de- termined very closely by noting the number of the last cone which melts. The cones are numbered from 022 to 39 and indicate temperatures from 590 to 1910 F., by ap- proximate increments of 20. Fig. 1, d, shows cones 010, 09, 08 and 07, of which only the last is unaffected, and, from the table furnished with the cones, this indicates a temperature of 1000 F. 4. Absolute Temperature: In experiments that have been carried on with pure gases with the use of air ther- mometers, it has been found that air expands approximately -j.^ of its volume per degree increase in temperature at zero F. or _1- of its volume at zero C. From the same line of reasoning, by cooling the air below zero, the reverse process should be equally true, that is, for each degree Fahrenheit of cooling the volume at zero would be contract- ed i Evidently, then, if a volume of gas could be cooled to 460 F., it would cease to exist. This theoretical point is called the absolute zero of temperature. All gases change to liquids or solids before this point is reached, however, and hence do not obey the law of contraction of gases at the very low temperatures. The fact that air at constant pressure changes its volume almost exactly in proportion to the abso- lute temperature, T, (460 + t, where t is temperature Fahren- heit) gives a starting point to be used as a basis for all air volume temperature calculations. For instance, if a volume of 20000 cubic feet be taken in at the air intake of a build- ing at 0, and heated to 70, its volume, by the heating, will ABSOLUTE TEMPERATURE AND PRESSURE 11 become greater in the same proportion that its absolute tem- x 530 p.erature becomes greater; that is, =: ; x = 23000 20000 460 cubic feet, or an increase of 15 per cent. GAGE AND ABSOLUTE PRESSURES. Two common ways of ex- pressing pressures are in use. One is denoted by the expres- sion pressure by gage, and refers to the total pressure in a container minus the pressure of one atmosphere. Thus the expression "65 pounds boiler pressure, by gage" means that the boiler is carrying 65 pounds pressure, per square- inch of surface, above the pressure of the atmosphere, which is, for approximate calculations, taken at the standard pres- sure of 14.696 pounds per square inch. Hence, the boiler carries within it a total pressure of 65 pounds plus 14.696 pounds or 79.696 pounds per square inch. This total pres- sure is what is known as absolute pressure, and when stated in pounds per square foot of area, is called specific pressure. Like the volume of a gas, so also the absolute pressure varies directly with the absolute temperature/ other things being constant. Hence the equation P V R T, where P is the absolute pressure in pounds per square foot, V is the volume of one pound in cubic feet, T is the absolute tem- perature, and R is a constant which for air is 53.22. From this equation, having given any two of the quantities, P, V or T, the third may be found. In very accurate calculations where the value 14.696 is not considered close enough, the barometer may be read, and its readings, in inches of mer- cury, multiplied by the constant .49, to obtain the pressure of the atmosphere in pounds per square inch. MECHANICAL EQUIVALENT OP HEAT. By precise experiment, it has been determined that, if the heat energy represented by one B. t. u. be changed into mechanical energy without loss, it would accomplish 778 foot pounds of work. Similarly, one calorie is equivalent to 428 kilogrammeters. One horse power of work is equivalent to the expenditure of 33000 foot pounds of work per minute. Hence one horse power of work represents 42.416 B. t. u. per minute. LATENT HEAT. Not all the heat applied to a body pro- duces change in temperature. Under certain conditions, the heat applied produces internal or molecular changes, and is called latent heat. Thus if heat is applied to ice at the freez- ing point, no rise of temperature is noted until all the ice 12 HEATING AND VENTILATION is melted; and again, heat applied to water at boiling point does not raise the temperature, but changes the water into steam. The first is called latent heat of fusion, and for ice is 142 B. t. u. per pound, while the latter is called latent heat of evaporation, and for water is 969.7 B. t. u. per pound. SPECIFIC HEAT. The ratio of the quantity of heat required to raise the temperature of a substance one degree, to that required to raise the temperature of water one degree from the temperature of its maximum density, 39.1 degrees, is commonly called the specific heat of the substance. Table 15, Appendix, gives 'specific heats of substances. 5. Radiation, Conduction and Convection: The trans- mission of heat, next to its generation, forms an item of vital interest to the heating engineer, for different forms of heat- ing installations are based fundamentally on the different ways in which heat is transmitted. These ways are usually quoted as being three in number radiation, conduction and convection. RADIATION. This transmission of heat occurs as a wave motion in the ether of space, and is the way by which the heat of the sun reaches the earth. Heat of this form, usu- ally referred to as radiant heat, requires no matter for its conveyance, passes through some materials, notably rock- salt, without change or appreciable loss, and travels, as does light, at the rate of 186000 miles per second. CONDUCTION. The second method of transmission is more commonly evident to the senses. If a rod of metal is heat- ed at one end, it is known that the heat is transferred, or conducted, along the rod until the other end becomes heated also. Conduction being, essentially, the way by which solids transfer heat, is hence of special significance in the calcu- lation of heat losses through the walls of a building. Rel- ative conductivity of a substance may be defined as the quantity of heat which passes through a unit thickness of the substance in a unit of time across a unit of surface of the substance, the difference of temperature between the two sides of the substance being one unit of the thermo- metric scale employed. Since the complexity of our build- ing constructions renders it obviously impossible to reduce all losses to losses per unit thickness of the structure, we are not permitted to use the term relative conductivity but another term, i. e., transmission constant, or rate of trans- HEAT TRANSMISSION 13 mission. Thus in Table IV, page 36, the rate of transmission K, given for a 6 inch studded frame wall, is .25 B. t. u. per square foot of surface per degree difference of temperature for one hour. It is readily seen that this table is the basis for the heat loss calculations of buildings. CONVECTION. Gases and liquids convey heat most readily by this method, which is funda- mental with hot air and hot water heat- ing installations. If it is attempted to heat a body of water by applying heat to its up- per surface, it will be found to warm up I. ^ with extreme slowness. If, however, the At _^r source of heat be applied below the body of water as in Fig. 2, it will be found to heat rapidly, the water being distributed by cir- Fig. 2. culating currents having more or less force, and following, in general, the direction shown by the arrows. What actually happens is this: water particles near the source of heat be- come lighter, volume for volume, than the cold- er particles near the top; then, because of the change in density, gravity causes an exchange of . these particles, drawing the heavier to the bottom and allowing the heated and lighter particles to rise to the top, thus forming the circulation currents. This process is known as convection. It will never occur unless the med- ium expands considerably upon being heated, and unless the force of gravity is free to es- tablish circulating currents. The hot water heating system may be considered merely as a body of water, Fig. 3, furnished with proper pipe circuits. When heated at one point, the water rises by convection to the radiators, is there cooled, hence becomes heavier, and de- scends by the return circuit to the point of heat application, thus completing the circuit. The warm air furnace installation works similarly, air, however, being the heat-carrying medium. n Fig. 3. CHAPTER n. AIR COMPOSITION VENTILATION, HUMIDITY. 6. Composition of Atmospheric Air: The subject of ventilation as applied to buildings would naturally be in- troduced by a brief consideration of the properties of the air supplied. This supply is a very important factor as re- gards both quality and quantity. In addition to its value as a heating medium, it determines, in a large measure, the health of the occupants of the building. The human body may be considered as a well equipped, although very complex, power plant. As the carbon, hydro- gen and oxygen in the fuel and air supply in any mechan- ical power plant are consumed in the furnace, the resulting heat absorbed in the generating system and finally turned into work through the attached mechanisms, so the human body in a similar way, but at a much slower rate, absorbs the heat of combustion and turns it into work. The prod- ucts of combustion in both cases are largely carbonic acid and water. The chief requisites of the mechanical plant are good fuel, good draft and good stoking. Similarly, the human body needs pure food, pure air and healthful exer- cise. Of the three, the second is probably of the greatest importance, since no person can keep in health with im- pure air, .even though accompanied with the best of food and plenty of exercise. Air, to the average person, is made up of two elements, oxygen and nitrogen, in the volume ratio of about 20.9 to 79.1 and a density ratio of about 23.1 to 76.9, respectively. We find in making a complete analysis of pure air, that a number of other elements and compounds enter into it, mak- ing a mechanical mixture which is somewhat complex. To the heating and ventilating engineer, however, two im- portant substances must be added to the two just stated, and a revision of the percentages will therefore be neces- sary. It may be said that pure air, as taken from the good open country and not contaminated with poisonous gases or the dust and refuse from the cities, would have about COMPOSITION OP AIR 15 the following composition. See Encyclopedia Britannica, Respiration. Oxygen Symbol O Per cent, of volume 20.26 Nitrogen " N " " " 78.00 Moisture " H 2 O " " " 1.7 Carbonic Acid " CO 2 " " " .04 These values are fairly constant, except that of the mois- ture, which may vary according to the humidity anywhere from + to 4 per cent, of the entire weight of the air. In places where the air is not pure, the following substances may be found in small quantities: Carbon Monoxide (CO), Sulphuretted hydrogen (H 2 S), Ozone, Argon, compounds of Ammonia, and compounds of Nitric, Nitrous, Sulphuric and Sulphurous acids. In the process of respiration, the lungs and the skin of the average person will change the composition of the air from that given above to Oxygen Per cent, of volume 16 Nitrogen " " " 75 Moisture 5 Carbonic Acid " " " 4 Comparing these values with those for pure air, it will be seen that the oxygen has been reduced about one-fifth, the nitrogen has been reduced about one twenty-fifth, the vapor has increased three times and the carbonic acid has increased one hundred times. Oxygen has been consumed in its uniting with the excess carbon and hydrogen in the system, and is given off as carbonic acid and water vapor. It may be seen from these ratios, that the very rapid increase in carbonic acid (rejected bodily tissue), would soon render unfit for use the air in almost any building occupied by a number of people. To avoid this state of affairs, fresh air should be supplied continuously and at such points as will provide the most uniform circulation. 7. Oxygen and Nitrogen: The oxygen of the air fills about one-fifth of the volume in atmospheric air and is the element that makes combustion possible. The other four- fifths of the space might be said to be filled with nitrogen. In a providential way, this nitrogen acts as a sort of buffer in its mixture with the oxygen and serves to control the rapidity with which the combustion takes place. Nitrogen seems to have little effect upon the respiration, except to retard the chemical action between the oxygen and carbon 16 HEATING AND VENTILATION and the oxygen and hydrogen. If one were to attempt to live in an atmosphere of pure oxygen, the chemical action in the lungs would be so rapid that the human body would not be able to maintain it. 8. Carbonic Acid: The amount of carbonic acid or carbon dioxide as it is sometimes called, as found in the air, is used as an index to the purity of the air. This is not considered a poisonous gas. The real action of the car- bonic acid when taken into the system is not well known. It has the effect of producing physical depression, and where fpund in sufficient quantity would even cause death. Whatever its effect upon human life may be, its presence in any room used for habitation i's usually an indication of the lack of oxygen. Pure air has four parts carbonic acid in 10000 parts of air, and room air should never be allowed to have more than eight to ten parts in 10000 parts of air. It becomes the problem of the heating engineer, therefore, to provide air in sufficient quantities, and to enter and withdraw the air from the room in a manner such as will not be uncomfortable to the occupants, at the same time keeping the air fairly uniform in quality, throughout the room. Carbonic acid in the exhaled breath is about five times heavier than air, and therefore, would have a tendency to fall. It is exhaled, however, with excessive moisture and at a temperature higher than that of the room air, both qualities giving it a tendency to rise. These latter factors probably neutralize the excessive density, and as long as the air is not absolutely quiet, the result is a fair diffusion throughout the room air. In large audiences the heat given off from the occupants is sufficient to cause strong air currents which, in rising, lift this impure air to the upper part of the room. A method of determining the percentage of carbon dioxide in the air, based upon the fact that barium carbonate is nearly in- soluble in water, may be performed as follows: Provide eleven bottles with rubber stoppers having two holes each, and connect them continuously by glass and rubber tubing, so that if suction be applied at the first bottle of the series, air will be drawn in at the last of the series and the same air will be passed through all. In this way a sample of the air to be tested may be drawn into each bottle. The capac- ities of the bottles must be mad.e to be respectively, in ounces, 23%, 18%, 16%, 14, 9%, 7%, 5%, 4, 3%, 2% and 2. DETERMINING THE PURITY OF AIR 17 This may readily be done by partially filling with parafflne. Into each bottle is then placed % ounce of a 50 per cent, sat- urated solution of barium hydrate, Ba(OH) 2 . More of the air to be tested is drawn through the system until assurance is had that each bottle contains a fair sample. Each bottle is then thoroughly shaken, so that the liquid may be brought into good contact with the air sample. If the least turbidity or cloudiness appears in the 'First or largest bottle indicates 0.04 per cent. CO 2 Second bottle indicates 0,06 " " " Third " " 0.07 " Fourth " " 0.08 " Fifth " " 0.10 " " " Sixth " " 0.15 Seventh " " 0.20 " Eighth Ninth Tenth Eleventh 0.30 0.40 0.60 0.90 Care must be taken to have a fair sample of the air in each bottle. The glass tubes through the rubber stoppers should extend no farther than the bottom of the stoppers. Fig. 4, a, shows four of the bottles and their connections. As an example, suppose that the air of a room was tested and that in the first, second, third, fourth, fifth and sixth bottles the liquid became turbid after vigorous shaking. Such room air would have contained 0.15 per cent, of carbon dioxide, and would have been considered quite unfit for breathing. Fig. 4. 18 HEATING AND VENTILATION A second, less cumbersome, and, more delicate method of testing for the percentage of carbon dioxide will be described, as it is the method commonly used and only requires comparatively simple apparatus, as shown in Fig. 4, (b). A bottle of about 6 ounces capacity is fitted with a rubber stopper hav- ing two holes. Through one hole a glass tube is brought from the bottom of the bottle, and to the outer end of the tube is connected a valved bulb similar to those found on atomizers. Into the bottle are placed 10 cubic centimeters of a, solution made by dissolving .53 grams of anhydrous sodium carbonate, Na 2 CO 3 , in 5 liters of water, and adding .01 gram of phenolphthalein. The water used must have been previously boiled for at least one hour in an open vessel. With the apparatus so prepared, squeeze the bulb, thus forc- ing air from the room through the liquid and into the bot- tle. The open hole in the rubber stopper is then closed with the thumb, and the bottle shaken while, say, twenty is counted, then another bulb-full of air is inserted, and again shaken. This process is continued and the number of bulbs of air noted until the red color of the solution, due to the phenolphthalein, disappears. This number of bulb fillings is indicative of the purity of the air according to the table below. After such an apparatus is completed, it must be calibrated before being used. This is done by testing the number of bulb fillings of pure country air necessary to clear the liquid, which will usually vary from 40 to 70. A new table for that special apparatus is then obtained from the one given below by proportion. In the table given, this number of bulb fillings, with purest country air, is 48. If, with the apparatus made up, it is found that, say, 60 bulb fillings are required, then the proportionate table would be made by multiplying the number of bulb fillings given below by the ratio of 60 -r- 48, or 5 to 4. It is important that the bulb be compressed the same amount for each filling, and that the shaking of the bottle and contents be continued the same length of time after each filling, to obtain uniform results. DETERMINING THE PURITY OF AIR 19 TABLE I. Fillings Per Cent CO 2 Fillings Per Cent CO a 48 .030 13 .08 40 .038 12 .083 35 .042 11 .087 30 .048 10 .09 28 .049 9 .10 26 .051 8 .115 24 .054 7 .135 22 .058 6 .155 20 .062 5 .18 19 .064 4 .21 18 .066 3 .25 17 .069 2 .30 16 .071 15 .074 14 .077 The methods outlined for the approximate estimation of CO 2 are satisfactory for determining whether or not ventila- ting systems maintain a proper degree of purity of air. If exact percentages of CO, CO 2 , O and N are required, the Orsat apparatus must be employed, for description of which see Engineering Chemistry by Stillman, page 238. See also Car- penter, H. & V. B., Chap. II, and Hempel's Gas Analysis, tran- slated by Dennis. 9. Amount of Air Required per Person: The need of a continuous supply of fresh air in our residence and business houses can scarcely be over-estimated. Health is probably the greatest of all blessings and pure air is absolutely es- sential to health. The average adult, when engaged in or- dinary indoor occupations, will exhale about twenty cubic inches of air per respiration. He will also have sixteen to twenty respirations per minute, making a total of 400 cubic inches or, say, .25 cubic foot of air exhaled per minute. If as in Art. 6, exhaled air contains 4 per cent. CO 2 , then the average person will exhale 60 x .25 x .04 = .6 cubic foot CO 2 per hour, (Pettenkofer, Smith & Parker), which is con- stantly being diffused throughout the air of the room, thus rendering it unfit for use. If this carbonic acid gas could be disassociated from the rest of the air and expelled from the room without taking large quantities of otherwise pure air with it, the problems of the heating engineer would be 20 HEATING AND VENTILATION simplified, but this cannot be done. Because of this rapid diffusion, it is necessary to flood the room with fresh air in order that the purity may be maintained at a safe value. The ideal conditions "would be to have it the same as that of the outside air, but the mechanical difficulties around such a ventilating 1 system would be so great as to render it prohibitive. The standard of purity which should be aimed at, and one, as well, which may be attained with a first class system, is, .06 of one per cent. CO 2 , i. e., six parts of CO 2 in 10000 parts of air. A system, however, which maintains a standard of eight parts in 10000 would be considered fairly satisfactory. This may be put in a simple form for calculation. Let Q L = cubic feet of atmospheric air needed per hour per person; A = cubic feet of COa given off per hour per person; n the standard of purity to be maintained (al- lowable parts of COo in 10000 parts of air); and p = the standard of purity in atmospheric air, say, 4; then If we wish to maintain a purity in the room of seven parts CO 3 in 10000 parts of air, and pure air contains four parts in 10000, we have Qi = . 6 4- (.0007 .0004) = 2000 cubic feet of air per hour. Another formula, quoted from Carpenter's Heating and Ventilating of Buildings, very similar to the above, is where a = the purity of the exhaled breath, say 400 parts in 10000, n the purity to be maintained in the room and 6 = the cubic feet of air exhaled per minute. Substituting, as above, Q L = (400 X 60 X .25) -=- (7 4) = 2000 cubic feet. Based upon .6 cubic foot of COs exhaled per person per hour, Table II gives the amount of air needed to maintain the various standards of purity. It should be understood that no hard and fast rule can be given for the air requirement per person. This, natur- ally, would be a different amount when considering the physical development for each person in health; it would also be different for the same person according to his occu- AIR REQUIRED PER PERSON 21 pation at the time, sleep being the least, waking rest somewhat greater, and physical exercise the greatest; but it is decidedly varying when considering the state of the person's health, or the sanitary value of his surroundings. According as the degree of purity is demanded, the air supply must be increased to suit it. TABLE II. Cubic F eet of Air per Person per Hour. n A Qi 6 .6 3000 7 .6 2000 8 .6 1500 9 .6 1200 10 .G 1000 Generally, it is understood that the average adult sub- jected to average conditions will require 1800 cubic feet of air per hour. The amount of air needed for ventilation then in most cases can be represented by the formula Q' = 1800 N, wnere N = the number of people to be provided for. The following table quoted from Carpenter's H. & V. B., and from Morin in Encyclopedia Britannica, gives a fair value for the amount of air per occupant per hour, that should be supplied to rooms used for various purposes. TABLE III. Hospitals, Ordinary 2000-2400 cu. ft. per hour. " Epidemic 5000 " " " " Work Shops, Ordinary 2000 " " Unhealthy trades ..3500 Prisons 1700 Theaters 1400-1700 " " Meeting halls 1000-2000 Schools, per child 400- 500 " " adult 800-1000 " " Recent practice would tend to increase these values somewhat; especially those relating to school bouse ventll- 22 HEATING AND VENTILATION ation, where a good estimate would be 800 to 1800 respec- tively. One ordinary gas burner of 20 candle power, using, say, four cubic feet of gas per hour, will vitiate as much air as three or four people. Where many lamps are used, this fact should be taken into account. In summing up the subject of ttie fresh air supply, it is well to call attention to the fact that the ordinary running conditions of any room cannot be absolutely determined by a single test for carbon dioxide. Trials should be frequently made and rec- ords kept. Upon one day the conditions may be unusually fav- orable and would show a small amount of CO 2 even though a very small amount of fresh air be admitted; while on other days, when the conditions are not so favorable, a large amount of fresh air would have to be supplied to maintain the proper purity within. If the only requirement, therefore, governing the ventilation of buildings should be that a satis- factory CO 2 test be passed, there would be a large oppor- tunity to overrate or underrate, as the case may be, the ven- tilating system of the building. The only safe method in rating ventilating systems is to require a minimum air supply in addition to a maximum permissible percentage of C0 2 , 10. Moisture with Air: Moisture with the air is a benefit to both the heating and ventilating systems in any room. With moisture in the room, a person may feel comfortable when the temperature is several degrees lower than the comfortable temperature of dry air. Dry air takes up the moisture from the skin. The vaporization of this moisture causes a loss of heat from the body, and gives to the per- son a sense of cold, which is only relieved when the tem- perature of the room is increased. Air space that is fairly saturated with moisture will not permit of much evaporation from the skin, because there is not much demand for this moisture with the air; consequently the body retains that heat and the person has a sensation of warmth which is only relieved by lowering the temperature of the air of the room. On the other hand, at low temperatures the mois- ture with air chills the surface of the skin by convection, a condition that is not so noticeable when the air is dry. It follows from the above statement that the range of com- fortable temperatures is less for moist air than for dry air. Concerning the effect of moisture in its relation to the heating and ventilating of the room, we may say that thor- MEASUREMENT OF HUMIDITY 23 oughly dry air has not the quality of intercepting- radiant heat; moisture, however, has this quality. Moist air has also somewhat less weight than dry air and is more buoyant. Because of the possibility of storing up the radiant heat within the particles of moisture, and, because of its con- vection qualities, it serves as a good heat carrier for the heating system. 11. Humidity of the Airt The actual humidity is the amount of moisture expressed in grains or in pounds per cubic foot, mixed with the air at any temperature. The relative humidity is the ratio of the amount of moisture actu- ally with the air divided by the amount of moisture which the same volume could hold at the same temperature when saturated. It is very important that the heating engineer be able to add to or to take away from the amount of the moisture in the air supply of any building. To find the amount of moisture that should be added or subtracted in any case, it is first necessary to determine the humidity of the air current at various points along its course. This may be obtained by the aid of the wet and dry bulb ther- mometer or by any one of a number of hygrometers supplied by the trade. The wet and dry bulb ther- mometer has a very simple appli- cation, and is probably in most gen- eral use. The principle of its ap- plication is as follows: having two thermometers, Fig. 5, let one of them register the temperature of the room air, the other one being kept wet by a cloth which covers the bulb and projects into a vessel filled with water, shown between the two thermometers. If the air Is saturated the two thermometers will record the same temperature; if, however, the air is not saturated the thermometer readings will dif- fer an amount depending upon the Fig. 5. humidity. It will readily be seen that the lowering of the temperature in the wet thermometer is due to the extraction of the heat in vaporizing the moisture from the bulb to the air. 24 HEATING AND VENTILATION In taking readings, let the mercury find a constant level In each thermometer and then note the difference in temper- ature between the two. In Table 10, Appendix, at this difference and at the room temperature read off the relative humidity; then take from Table 9, Appendix, the amount of moisture with saturated air at the temperature recorded by the dry thermometer, and multiply this by the humidity. The result is the amount of moisture with the air per cubic foot of volume. APPLICATION. Room air, 70 degrees; difference in readings, 6 degrees. From Table 10, the humidity is 72 per cent. From Table 9, col. 7, .72 X .001153 = .00083 pounds per cubic foot. To avoid the necessity for the use of tables, various in- struments have been designed, which, graphically, give the relative humidity directly. Fig. 6, shows such an instrument, Fig. commonly known as the Jiygrodeik. To find, by it, the relative humidity in the atmosphere, swing the index hand to the left of the chart, and adjust the sliding pointer to that de- gree of the wet bulb thermometer scale at which the mer- cury stands. Theoi swing the index hand to the right until MEASUREMENT OP HUMIDITY 25 the sliding pointer intersects the curved line which extends downward to the left from the degree of the dry bulb thermometer scale, indicated by the top of the mercury column in the dry bulb tube. At that intersection, the in- dex hand will point to the relative humidity on scale at bot- tom of chart. Should the temperature indicated by the wet bulb thermometer be 60 degrees and that of the dry bulb 70 degrees, the index hand will indicate humidity of 55 per cent., when the pointer rests on the intersecting line of 60 degrees and 70 degrees. For accurate work any instrument of the wet and dry bulb type should be used in a current of air of not less than 15 feet per second. 12. For Close Approximation* and to avoid calculations, the humidity chart, Fig. 7, may also be used in determining relative humidity, absolute humidity, dew point, temperature of wet bulb and temperature of dry bulb. On the left of the chart is a scale referring to horizontal lines giving tempera- tures of the wet bulb. The scale on the right hand, referring to the lines curving downward from right to left, is the scale of the room, or dry bulb, temperatures. The scale along the bottom of the chart is one of relative humidity. The scale of numbers up the center of the chart refers to the lines curving downward from left to right, and indicates the absolute hu- midity, i. e., grains of moisture per cubic foot with the air. The use of the chart may be most readily understood by a few applications. APPLICATION. Given dry bulb 70 degrees and wet bulb 60 degrees. Determine relative humidity, absolute humidity, temperature of dew point for room, etc. First, starting on the right hand scale at 70, follow down the line this number refers to until it crosses the horizontal line of 60 degrees, wet bulb temperature. From this intersection drop to the relative humidity scale and read there 55 per cent. This may be checked with the table. To obtain the absolute humidity will be noticed that the intersection of the 70 degree and C- o o >ER CENT Fig. 7. HUMIDIFYING THE AIR 27 <2*>ord t >i a s i & o o low 15 per cent, for pantry stair and exposure low for floor and hall way on second floor low 10 per ct. for exposure 9 1 "o tn S-i i i 10 ;-, O Is M o o> Add closet to room Allow 10 per cent.for closet and exposure 3 5J 3 * * Diameter of grate allowing ventilation for ten people = 24 inches. Cold air duct = 569 square inches = 18 X 32 inches. In selecting the various stacks and leaders it would be well to standardize as much as possible and avoid the extra expense of installing so many sizes. This can be done if the net area is not sacrificed. BURNACE HEATING 57 Fig. 33. 58 HEATING AND VENTILATION FURNACE HEATING 59 5ctonD FIPOR. PLAN Fig. 15. CHAPTER V. FURNACE HEATING AND VENTILATING. SUGGESTIONS ON THE SELECTION AND INSTALLATION OF FURNACE HEATING PARTS. 49. Selection of the Furnace: In selecting a furnace for residence use or other heating service, special attention should be paid to the following- points: easy movement of the air, arrangement and amount of heating surface, shape and size of the fire pot, method of feeding fuel to the fire and type and size of the grate. The furnace gases and the air to be heated should not be allowed to pass through the furnace in too large a unit volume or at too high a velocity. The gases should be broken up in relatively small volumes, thus giving an opportunity for a large heating surface. Concerning the gas passages themselves, it may be said that a number of small, thin passages will be found more efficient than one large passage of equal total area. This is plainly shown in a similar case by comparing the effi- ciency of the water-tube or tubular boiler with that of the old fashioned flue boiler; i. e., a large heating surface is of prime importance. Again, it is desirable that the total flue area within the furnace should be great enough to allow the passage of large volumes of air at low velocities, rather than small volumes at high velocities. This permits of less forcing of the fire and consequently lowers the tem- perature of the heating surface. The latter point will be found valuable when it is remembered that metal at high temperatures transmits through its body a greater amount of impure gases from the coal than when at low tempera- tures. Concerning velocities, it may be said that on account of the low rate of transmission of heat to or from the gases, long flue passages are necessary, so that gases mov- ing at a normal rate will have time to give off or to take up a maximum amount of heat before leaving the furnace. Air is heated chiefly by actual contact with heated sur- faces and not much by radiation. Consequently, the ef- ficiency of a furnace is increased when it is designed so that the gases a>nd air in .their movement impinge perpen- dicularly upon the heated surfaces at certain places. This FURNACE HEATING 61 point should not be so exaggerated that there would be serious interference with the draft. The efficiency is also increased if the general movement of the two currents be in opposite directions. Furnaces for residences are usually of the portable type, Fig. 16, the same being enclosed in an outer shell composed of two metal casings having a dead air space or an asbes- tos insulation between them. Some of the larger sized Fig. 16. plants, however, have the furnace enclosed in a permanent casement of brick work, as in Fig. 17. Each of the two types of furnaces give good results. The points usually governing the selection between portable and permanent settings are price and available floor space. The cylindrical fire pot is probably better than a con- ical or spherical one, there being less danger of the fire clogging and becoming dirty. A lined fire pot is better than an unlined one, because a hotter fire can be maintained in it with less detriment to the furnace. There is of course a loss of heating surface in the lined pot, and in some forms of furnaces the fire pot is unlined to obtain this increased 62 HEATING AND VENTILATION heating surface. It seems reasonable to assume, however, that the lined pot is longer lived and contaminates the air supply less. Pig. 17. Fig. 18. FURNACE HEATING 63 Some form of shaking or dumping grate should be se- lected, as a stationary grate is far from satisfactory. Care should be exercised also in the selection of the movable grate, as some forms not only stir up the fire but permit much of it to fall through to waste when being operated. The fuel is fed to the fire pot from the door above the fire. This is called a top-feed furnace. In some forms, how- ever, the fuel is fed up through the grate. This is called the under-feed furnace, Fig. 18, and is rapidly gaining in favor. The latter type requires a rotary ring grate with the fuel entering up through its center. The size of the furnace may be obtained from the estimated heating capacity in cubic feet of room space as given in the sample Table 16, Appendix. Another and perhaps a bet- ter way, and one that serves as a good check on the above, is to select a furnace from the calculated grate area. See Art. 46. Having selected the furnace by the grate area, check this with the table for the estimated heating capacity and the heating surface to see if they agree. What is known as a combination heater is shown in Fig. 19. It is used for heating part of the rooms of a resi- dence by warm air, as in regular furnace work, and the remainder of the rooms by hot water. In this manner, rooms to be ven- tilated as well as heated may be connected by the proper stacks and leaders to the warm air deliveries of such a combination heater, while rooms requir- ing less ventilation or heat only may have radiators installed and connected to the flow and return pipes shown In the figure. Also, because of the difficulty in heating certain exposed rooms, with warm/ air, these rooms may be supplied by the positive heat of the Fig. 19. more reliable water circulation. 64 HEATING AND VENTILATION 50. Location of the Furnace: Where other things do not interfere, a furnace should be set as near the center of the house plan as possible. Where this is not wise or possible, preference should be given to the colder sides, say the north or west. In any case, it is advisable to have the leader pipes as near the same length as can be made. The lengtn of the smoke pipe should be as short as possible, but it will be better to have a moderately long smoke pipe and obtain a more uniform length of leader pipes than to have a short smoke pipe and leaders of widely different lengths. The furnace should be set low enough to get a good upward slope to the leaders from the furnace to their re- spective stacks. This should be not less than one inch per foot of length and more if possible. These leader pipes should be dampered near the furnace. The location of the furnace will call forth the best judgement of the designer, since the right or wrong decis- ion here can make or mar the whole system more com- pletely than in any other manner. 51. Foundation: All furnaces should have directions from the manufacturer to govern the setting. Each type of furnace requires a special setting and the maker should be-t be able to supply this desired Information concerning it. Such information may be safely followed. In any case the furnace should be mounted on a level brick or concrete foundation specially prepared and well finished with cement mortar on the inside, since this interior is in contact with the fresh air supply. 52. Fresh Air Duct: This is best constructed of hard burned brick, vitrified tile or concrete, laid in four inch walls with cement mortar and plastered inside with ce- ment plaster, all to be air tight. The top should be covered with flag stones with tight joints. The riser from this, leading to the outside of the building, may be of wood, tile or galvanized iron, and the fresh air entrance should be vertically screened. The whole should be with tight joints and be so constructed as to be free from surface drainage, dirt, rats and other vermin. This duct may be made of metal or boards as substitutes for the brick, tile or concrete. Board construction is not so satisfactory, although it is the FURNACE HEATING cheapest, and whenever used should be carefully constructed, An opening- may be made in the fresh air duct near the furnace for the purpose of admitting the duct which carries the recirculated air from the rooms to the furnace. Both of these ducts should have dampers that may be opened or closed. See Fig. 12. Both ducts should also be provided with doors that can be opened temporarily to the cellar air. Sometimes it is desirable to have two or more fresh air ducts leading- from the different sides of the house to the furnace so as to get the benefit of any change in air pressure on the outside of the building. Proper arrangements may be made for pans of clear water in the air duct near the furnace to give moisture to the air current, although only a small amount of moisture will be taken up at this point. In most cases where moistening pans are used, they are installed in con- nection with the furnace itself. A good way to moisten the air fs to have moistening pans built in just behind the register face, Fig. 20. These pans are shallow and should not be permitted to seriously inter- fere with the amount of air enter- ing- through the register. Fig. 20. 53. Recirculatlng Duct: A duct should be provided from some point within the building, through the cellar and entering into the bottom of the furnace or into the fresh air duct near the furnace; this is to carry the warm air from the room back to the furnace to be reheated for use again within the building. In many cases tin or gal- vanized iron is used for the material for the recirculating pipe. Where this enters the furnace, or the fresh air duct near the furnace, it should be planned with sufficient turn so that the air would be projected through the furnace, thus placing a hindrance to the fresh cold air from following back through this pipe to the rooms. The exact location of the same will depend, of course, on the location of the register installed for this purpose. The construction of the 66 HEATING AND VENTILATION duct may agree with the similar construction of the fresh air duct. 54. Leader Pipes: All leader pipes should be round and free from unnecessary turns. They should be made from heavy galvanized iron or tin and should be laid to an upward pitch of not less than one inch per foot of length, and more if it can possibly be given. The connections with the furnace should be straight, but if a turn is necessary, provide long radius elbows. All connections to risers or stacks should be made through long radius elbows. Rect- angular shaped loots having attached collars are sometimes used, but these are not so satisfactory because of the im- Fig. 21. FURNACE HEATING pirigemcnt of the air against the flat side of the stack; also because of the danger of the leader entering too far into the stack and thus shutting off the draft. Leaders should connect to the first floor registers by long radius el- bows. Leader pipes should have as few joints as possible and these should be made firm and air tight. Fig. 21 shows different methods of connecting between leaders and stacks, also between leaders and registers. The outside of all leader pipes should be covered to avoid heat loss and to provide additional safety to the plant. The covering is usually one or more thicknesses of asbes- tos paper or mineral wool. 55. Stacks or Risers: The vertical air pipes leading to the registers are called stacks or risers. They are rect- angular or oblong in section and are usu- ally fitted within the wall. See Big. 22. The size of the studding and the distances they are set, center to center, limit the effective area of the stack. All stacks should be insulated to protect the wood- work. This is done by making the stack small enough to clear the woodwork by at least one-quarter inch and then wrapping it with some non-conducting material such as asbestos paper held in place by wire. Another way, and one which is prob- ably more satisfactory, is to have pat- ented double walled stacks having an air space between the walls all around. The outside wall is usually provided with vent holes which allow the circulation of air between the walls, thus protecting any one part from becoming overheated. All stacks should be made with tight joints and should have ears or flaps for fasten- ing to the studding. Patented stacks are made in standard sizes and of various lengths. The sizes ordinarily found in practice are about as given in Table 17, Appendix. A stack is sometimes run up in a corner or in some recess in the wall of a room where its appearance, after Fig. 22. 68 HEATING AND VENTILATION being finished in color to compare with that of the room, would not be unsightly. This is necessary in any case where the stack is installed after the building is finished. This method is desired by some because of its additional safety and because more stack area may be obtained than is possible when placed within a thin wall. All stacks should be located in partition walls looking toward the outside or cold side of the room. This protects the air current from excessive loss of heat, as would be the case in the outside walls. It also provides a more uniform distribution of air. The area of the stack best adapted to any given room is another point in furnace work which brings out a wide diversity of practice. Results from different installations show variations as great as 50 per cent. This is not so noticeable in the first floor rooms as it is in those of the second floor. In a great many cases the architect specifies light partition walls between large upper rooms, say, four inch studding set sixteen inch centers, between twelve foot by fifteen foot rooms, heavily exposed. From theoretical calculation of heat losses, these rooms require larger stacks than can be placed between studding as stated; however, it is very common to find such rooms provided for in this way. One possible excuse for it may be the fact that the room is designed for a chamber and not for a living room. Any sacrifice in heating capacity in any room, even though it be used as a sleeping room only, should be done at the sug- gestion of the purchaser and not at the suggestion of the architect or engineer. Every room should be provided with facilities for heat as though it were to be used as a living room in the coldest weather, then there would be fewer complaints of defective heating plants and less migrating from one side of the house to the other on cold days. This lack of heating capacity for any room is some- times overcome by providing two stacks and registers in- stead of one. This plan is very satisfactory because one of the registers may be shut off in moderate weather. How- ever, it requires an additional expense which is scarcely justified. A possible improvement would be for the archi- tect to anticipate such condition and provide suitable partition walls so that ample stack area could be put in. The ideal conditions will be reached when the architect act- FURNACE HEATING ually provides air shafts of sufficient size to accommodate either a round or a nearly square stack. When this time comes a great many of the furnace heating 1 difficulties will have been solved. A double stack supplying air to two rooms is some- times used, having a partition separating the air currents near the upper end. This practice is questionable because of the liability of the pressure of air in the room on the cold side of the house forcing the heated air to the other room. A better method is to have a stack for each room to be heated. 56. Vent Stacks: Vent stacks should be placed on the inner or partition walls and should lead to the attic. They may there be gathered together in one duct leading to a vent through the roof if desired. 57. Air Circulation Within the Room: The location of the heat register, relative to the vent register, will deter- Fig. 23. mine to a large degree the circulation of the air within the room. Fig. 23, a, b, c and d, shows clearly the effect of the different locations. The best plan, from the standpoint of heating, is to enter the air at a point above the heads of the 70 HEATING AND VENTILATION occupants and withdraw it from the floor line, at or near the same side from which the air enters. This gives a more uni- form distribution as shown by the last figure. It is doubtful, however, if this method will give the best ventilation in crowded rooms where the foul air naturally collects at the top of the room. Furnace heating is not so well cared for in this regard as are the other forms of indirect heating, the air being admitted at the floor line and required to find its own way out. 58. Fan Furnace Heating System: In large furnace installations where the air is carried in long ducts that are nearly, if not quite, horizontal, and where a continuous sup- ply of air is a necessity in all parts of the building, a com- bination fan and furnace system may be installed. These are frequently found in hospitals, schools and churches. Such a system may be properly designated a mechanical warm air system. In comparison with other mechanical systems, however, it is simpler and cheaper. The arrangement may be illustrated by Fig. 66 with the tempering coils omitted and the furnace substituted for the heating coils. The fan should .always be between the air inlet and the furnace so as to keep a slight pressure above atmosphere on the air. side and thus reduce the leakage of the fuel gas through the joints of the furnace. By this arrangement there is less volume of air to be handled by the fan and a smaller sized fan may be used. Fan-furnace systems may be set in multiple if desired, i. e., one fan "operating in connection with two or more fur- naces. Paddle wheel fans are preferred, although the disk wheel may be used where the pipes are large and where the air must be carried but short distances. For fan types see Chapter IX. 59. Suggestions for Operating Furnaces: Furnaces are designated hard coal and soft coal, depending upon the type and the construction of the grate, hence the grade of coal best adapted to the furnace should be used. The size of the open- ings in the grate should determine the size of the coal used. Keep the fire pot well filled with coal and have it evenly distributed over the grate. Keep the fire clean. Clinkers should be removed from the fire once or twice daily. It is not necessary to stir the fire so completely as to waste the coal through the grate. FURNACE HEATING 71 When replenishing a poor fire do not shake the fire, but put some coal on and open the drafts. After the coal is well ignited then clean the fire. The ash pit should be frequently cleaned, because an accumulation of ashes below the grate soon warps the grate and burns it out. Keep all the dampers set and properly working. Have a damper in the smoke pipe and keep it open only so far as is necessary to create a draft. Keep the water pans full of water. Clean the furnace and smoke pipe thoroughly in all parts at least once each year. Keep the fresh air duct free from rubbish and impurities. Allow plenty of pure fresh air to enter the furnace at all times. In cold weather part of this supply may be cut off. Have the basement well ventilated by means of outside wall ventilators, or by special ducts leading to the attic. Never permit the basement air to be circulated to the living rooms. To bank the fires for the night, clean the fire, push the coals near the rear of the grate, cover with fresh fuel to the necessary depth (this will be found by experience), set the drafts so they are nearly closed and partially open the fire doors. 72 HEATING AND VENTILATION REFERENCES. References on Furnace Heating:. TECHNICAL BOOKS. Snow, Prin. of Heat, p. 27. Snow, Furnace Heat., p. 7. I. C S., Prin. of Heat. & Vent., p. 1237. Carpenter, Heat. & Vent. Bldgs., p. 310. Hubbard, Power, Heat. & Vent., p. 423. TECHNICAL PERIODICALS. Engineering Review. Warm Air Furnace Heating, C. L. Hub- bard, Nov. 1909, p. 42; Dec. 1909, p. 45; Jan. 1910, p. 66; Feb. 1910, p. 48; March 1910, p. 51; May 1910, p. 48; Aug. 1910, p. 29. Warm Air System of Heating and Ventilating, R. H. Bradley, May 1910, p. 32 Mechanical Furnace Heating and Ventilating, June 1910, p. 49. Heating and Vent. System installed in Public School, Fairview, N. J., July 1910, p. 47. Combined System of Warm Air and Hot Water Heat, for a Residence, Jan. 1909, p. 26. Warm Air Heating Installation in a Brooklyn Residence, March 1909, p. 38. The Heating and Ventilating Magazine. Advanced Methods of Warm Air Heat- ing, A. O. Jones, Aug. 1904, p. 88. Air Pipes, Sizes Required for Low Velocities, Oct. 1905, p. 7. Report of Committee (A. S. H. V. E.) to Collect Data on Furnace Heating, Jan. 1906, p. 35. An Improved Application of Hot Air Heating, A. O. Jones, July 1906, p. 31. Domestic Engineering. Sanitation in Hot Air Heating, James C. Bayles, Vol. 25, No. 6, Sept. 25, 1903, p. 261. Trans. A. 8. H. & V. E. Test of Hot Air Grav- ity System, R. C. Carpenter, Vol. IX, p. 131. Heat Radiators using Air instead of Water and Steam, Geo. Alysworth, Vol. IX, p. 259. Velocities in Pipes and Registers in a Warm Air System, Vol. XII, p. 352. Relative Size Hot Air Pipes, Vol. XIII, p. 270. Velocity of Air in Ducts, Vol. VII, p. 162. CHAPTER VI. HOT WATER AND STEAM HEATING. DESCRIPTION AND CLASSIFICATION OF THE SYSTEMS. 60. Hot "Wafer and Steam Systems Compared to Fur- nace Systems: As compared to the warm air or furnace plant, the hot water and the steam installations are more complicated in the number of parts; they use a more cum- bersome heat carrying medium, for which a return path to the boiler must be provided; and have parts, in the form of radiators, which occupy valuable room space. But the steam and hot water plants have the advantage in that their circulations, and hence their transference of heat, are quite positive, and not affected by wind pressures. A hot water or a steam system will carry heat just as readily to the windward side of a house as it will to the leeward side, a point which, with a furnace installation, is known to be quite impossible. F urnace heating, on the other hand, has the advantage of inherent ventilation, while the hot water and steam systems, as usually installed, provide no ventilation except that due to air leakage. 61. The Parts of Hot Water and Steam Systems: A hot water or a steam system may be said to consist of three principal parts: first, the boiler or heat generator; second, the radiators or heat distributors; and third, the connecting pipe-lines, which provide the circuit paths for the hot water or the steam. In the hot water system it is essential that the heat generator be located at the lowest point in the circuit, for, as was explained in Art. 5, the only motive force is that due to the convection of the water. In the steam system this is not essential, as the pressure of the steam forces it outward to the farthest points of the system. The water of condensation may or may not be returned by gravity to the boiler. Hence, with a steam system a radiator may be placed below the boiler, if its condensation be trapped or otherwise taken care of. 74 HEATING AND VENTILATION 62. Definitions: In speaking of the piping of heating installations, several terms, commonly used by heating en- gineers, should be thoroughly understood. The large pipes in the basement connected directly to the source of heat, and serving as feeders or distributors of the heating me- dium to the pipes running vertically in the building, are known as mains. The flow mains are those carrying^ steam Fig. 24. Pig. 21 or hot water from the source of heat towards the radiators, and the return mains are those carrying water or condensation from the radiators to the source of heat. Those vertical pipes in a building to which the radiators are directly connected are called risers, while the short horizontal pipes from risers to radi- ators are usually termed riser arms. As there are flow mains and return mains, so also, there are flow risers and return risers. A radiator should have at least two tappings, one below for the entry of the heating medium, and one on the end section opposite, near the top for air discharge as shown by the connected steam radiator of Fig. 24. It may have three, a flow tapping and a return tapping at the bottom of the two end sections, and the third or air tapping near the top of the end section at the return end as shown by the connected hot water radiator of Fig. 25. A return HOT WATER AND STEAM HEATING 75 main traversing the basement above the water line of the boiler is designated as a dry return and carries both steam and water of condensation; one in such position below the water line as to be filled with water is designated a wet return, and the returns of all two-pipe radiators connecting with wet returns are said to be sealed. 63. Classification: One classification of hot water and steam systems is based upon the position and manner in which the radiators are used. The system which is, per- haps, most familiar is the one wherein radiators are placed directly within the space to be heated. This heating is ac- Fig. 26. Big. 27. complished by direct radiation and by air convection cur- rents through the radiators, no provision being made for a change of air in the room. This is known as the direct system, and, while it causes movements of the air in the room, it produces no real ventilation. See Fig. 26. In the direct-indirect system, the radiator is also placed within the space or room to be heated, but its lower half is so encased and connected to the outside of the build- HEATING AND VENTILATION ing that fresh air is continually drawn up through the radiator, is heated, and thrown out into the room as sfoown by Fig 1 . 27. Thus is established a ventilating system mor^ or less effective. In the purely indirect system, Fig. 28, 'the radiating sur- face is erected somewhere remote from the rooms to be neated, and ducts carry the heated air from the radiator to the rooms either by natural convection, as in some in- stallations, or by fan or blower pressure, as in others. When all the radiation for an entire building is installed Fig. 28. together in one basement room, and each room of the build- ing has carried to it, its share of heat by forced air through ducts from one large centralized fan or blower, the system is called a Plenum System, and is given special consideration in Chapters IX to XL 64. A second classification of steam and hot water sys- tems is made according to the method of pipe connection between the heat generator and the radiation. That known as the one-pipe system, Fig. 29, is the simplest in construc- tion and is preferred by many -for the steam installations. As the name indicates, its distinguishing feature is the single pipe leading from the source of heat to the radiator, the steam and the returning condensation both using this path. In the risers and connections, the steam and con- densation flow in opposite directions, thus requiring larger pipes than where a flow and a return are both provided. In this system the condensation usually flows with the steam in the main, and not against it, until it reaches such a point that it may be dripped to a separate return and then led to the boiler. In the so-called one-pipe hot water system, radiators have two tappings and two risers, but the flow riser is tapped out of the top of the HOT WATER AND STEAM HEATING 77 Fig. 29. single basement main, while the return riser is tapped into the bottom of that same main by either of the special fit- tings shown in section in Fig. 30. The theory is that the hot water from the boiler travels along the top of the horizontal base- ment main, while the cooler water from the radiators travels along the bottom of this same main. Hence the neces- sity for tapping flow risers out of the top and return risers into the bottom of this main, thus avoiding a mixing of the two streams. Where mains are short and straight as in the smaller Pig-. 30. residence installations, this system 78 HEATING AND VENTILATION seems to give satisfaction; but it is very evident that, where basement mains are long and more complicated, a mixing f the two streams is unavoidable, thus rendering the sys- tem unreliable. The two-pipe system is used on both steam and hot water installations. For steam work it is probably no better than the one-pipe system but for hot water work it is much preferred. In this system two separate and dis- tinct paths may be traced from any radiator to the source of heat." In the basement are two mains, the flow and the return, and the risers from these are always run in pairs, the flow riser on one side of a tier of radiators, the return riser on the other side. A two-pipe steam system must have a sealed return. Typical two-pipe main and riser con- nections are shown in E ig. 31. Fig. 31. Fig. 32. 65. A third system, known as the attic main, or Mills system, has found much favor with heating engineers in the installation of the larger steam plants although it could HOT WATER AND STEAM HEATING 79 be applied as well to the larger iiot water plants. The distinguishing- feature, when applied to a steam system, is the double main and single riser, so arranged that the condensation and live steam flow, in the same direction. This is accomplished by taking the live steam directly to the attic by one large main, which there branches, as need be, to supply the various risers, only one riser being used for each tier of radiators and the direction of flow of both steam and condensation in risers being downward. Hence, this system avoids the unsightliness of duplicate risers, as in the two-pipe system, and avoids the disadvantage of the one-pipe basement system, the last named having steam and condensation flowing in opposite directions in the same pipe. Fig. 32 shows two common methods of connecting risers and radiators with this system. 66. Vacuum Systems for Steam: Most commonly, the systems mentioned, when steam, are installed as the so- called low pressure systems, which term indicates an abso- lute pressure of about 18 pounds per square inch or 3Y 2 pounds gage pressure. On extensive work, it has been found advantageous to install a vacuum system to increase economy, also to insure positive steam circulation by prompt removal of condensation through vacuum returns. Even for comparatively small residence installations vacuum ap- plications of various kinds are becoming common. Vacuum systems may be divided into two classes, ac- cording to the way in which the vacuum is maintained. For comparatively small plants, not using exhaust steam, the vacuum is maintained by mercury seal connections, and these plants are usually referred to as mercury seal vacuum systems. These mercury seals may be attached to any standard one or two-pipe system by merely replacing the ordinary air valve by a special connection, which in real- 81) HEATING AND VENTILATION ity is only a barometer. An iron tube, Fig. 33, dips just below the surface of the mercury in the well on the floor, and extends vertically to the radiator air tap- ping to which the tube connects by a fitting which will allow air to pass into and through the barometer, but will not allow steam to pass. When the system is first fired up and steam is raised to several pounds gage, the air leaves all the radiators by bubbling through the mercury seal at the end of the vertical iron tube. If the fire is then allowed to go out, the steam will condense, and produce an almost perfect vacuum in the entire system, provided all pipe fitting has been carefully done. This system may be operated as a vacuum system at 4 or 5 pounds absolute pressure and have the water boiling as low as 150 to 160 degrees. The flexibility of this system recommends it highly. Applied to a residence or store, the plant may be operated during the day at sev- eral pounds gage pressure, if necessary, but when fires are banked for the night, steam re- mains in all pipes and radiators as long as the temperature of the water does not fall much below 150 degrees. This is in sharp contrast with the ordinary system, where steam disap- pears from all radiators as soon as the water temperature drops below 212 degrees. The promptness with which heat may be obtained in the morn- ing is noteworthy, for, if the vacuum has been maintained, steam will begin to circulate as soon as the water has been raised to about 150 degrees. According to demands of the weather, the radiators may be kept at any temperature along the range of 150 to 220 degrees, thus giving great flexibility. Instead of having a barometric tube at each radiator, one mercury seal may be supplied in the basement, and the air tappings of all radiators connected to the top of the tube by ^4 inch piping. The Trane vacuum system is usually so installed, and is an excellent example of this vacuum type. I HOT WATER AND STEAM HEATING 81 67. The second class of vacuum systems includes those designed especially for use in office buildings, and where- in the vacuum is maintained by an aspirator, exhauster or pump of some description. This exhauster may handle only the air of the system, that is, it may be connected only to the air tappings of all radiators, as in the Paul system, Fig. 34, or the exhauster may handle both air and con- densation and be connected to the return tappings of all radiators, as in the Webster system, Fig. 35. The Paul Fig. 34. Fig. 35. system is fundamentally a one-pipe system, using exhaust cr live steam and maintaining its circulation without back pressure, by exhausting each radiator at its air tapping, and also exhausting the condensation from the basement tank in which it has been collected by gravity. For an aspirator this system uses either air, steam, or hot water, as the conditions may determine. The Webster system is fundamentally a two-pipe system and exhausts from the radiators both the air and water of condensation, all radi- ator returns being- connected to the (usually) steam driven vacuum pump. These systems are designed to use both exhaust and live steam, and hence are finding wide application in the modern heating of manufacturing plants. See also Chapter XII. CHAPTER VII. HOT WATER AND STEAM HEATING. RADIATORS, BOILERS, FITTINGS AND APPLIANCES- The various systems just described are merely different ways of connecting the source of heat to the distributors of heat, i. e., methods of pipe connections between heater and radiators. Many forms of radiators exist, as well as many types of heaters and boilers, each adapted to its own peculiar condition. It is in this choice of the best adapted material where the heating engineer shows the degree of his practical training, and the closeness with which he fol- lows the latest inventions, improvements and applications. 68. Classification as to Material: Radiators may be classified, according to material, as cast iron radiators, pressed steel radiators and pipe coil radiators. Cast radi- ators have the hollow sections cast, as one piece, of iron. The wall is usually about % inch to % inch thick, and is finally tested to a pressure of 100 pounds per square inch. Sections are joined by wrought iron nipples which, at the same time, serve to make passageways between any one section and its neighbors for the current of heating me- dium, whether of steam or hot water. Cast iron radiators have the disadvantage of heavy weight, danger of break- ing by freezing, occupying much space, and having a com- paratively large internal volume, averaging a pint and a half per square foot of surface. Pressed radiators are made of sheet steel of No. 16 gage, and, after assembly, are galvanized both inside and out. Each section is composed of two pressed sheets that are joined together by a double seam as shown at a, Fig. 36, which illustrates a section through a two-column unit. Fig. 36. The joints between the sections or units are of the same kind. It is readily seen that such construction tends to- ward a very compact radiating surface. Pressed radia- HOT WATER AND STEAM HEATING 83 tors are comparatively new, but, in their development, promise much in the way of a light, compact radiation. In comparison with the cast iron radiators, they are free from the sand and dirt on the inside, thus causing less trouble with valves and traps. The internal volume will approxi- mate one pint per square foot of surface. See Fig. 37. Radiators composed of pipes, in various forms, are commonly referred to as coil radiators. They are daily becoming less common for direct and direct-indirect work, because of their extreme unsightliness. Piping is still much used as the heat radiator in indirect and plenum systems, although both cast and pressed radiators are now designed for both of these purposes where low pressure steam is used. In all coil radiator work, no matter for what purpose, 1 inch pipe is the standard size. However, in some cases pipes are used as large as 2 inches in diam- eter. This 1 inch pipe is rated at 1 square foot of heating surface per 3 lineal feet and has about 1 pint of containing capacity per square foot of surface. 69. Classification as to Form: Radiators may again be classified in accordance with form, into' the one, two, three, and four-column floor types, the wall type, and the flue type. See Fig. 37. These terms refer only to cast and pressed radiators. By the column of a radiator is meant one of the unit fluid-containing elements of which a sec- tion is composed. When the section has only one part or vertical division, it is called a single-column or one-column type; when there are two such divisions, a two-column; when three, a three-column; and when four, a four- column type. What is known as the wall type radiator is a cast section one-column type so designed as to be of the least practicable thickness. It presents the appear- ance, often, of a heavy grating, and is so made as to have from 5 to 9 square feet of surface, according to the size of the section. One-column floor radiators made with- out feet are often used as wall radiators. A flue radiator is a very broad type of the one-column radiator, the parts being so designed that the air entering between the sections at the base is compelled to travel to the top of the sections before leaving the radiator. This type is therefore well adapted to direct-indirect work. See Fig. 37. HEATING AND VENTILATION Stairway Type Dining Room Type Flue Type Circular Type CAST RADIATORS Wall Type Two-Column Type Three-Column Type Four-Column Type PRESSED RADIATORS Single-Column Two-Column Type Type Three-Column Type Fig:. 37. Wall Type HOT WATER AND STEAM HEATING 85 Many special shapes of assembled radiators will be met with, but they will always be of some one of the fun- damental types mentioned above. For instance, there are "stairway radiators," built up of 'successive heights of sections, so as to fit along the triangular shaped wall under stairways; there are "pantry" radiators built up of sections so as to form a tier of heated shelves; there are "dining room" radiators with an oven-like arrangement built into their center; and there are "window radiators" built with low sections in the middle and higher ones at either end, so as to fit neatly around a low window. Fig. 37 shows a number of these common forms as used in practice. 70. Classification as to Heating Medium: A third class- ification of radiators, according to heating medium em- ployed, gives rise to the terms steam radiator and hot water radiator. Casually, one would notice little difference between the two, but in construction there is a vital differ- ence. Steam radiation has the sections joined by nipples along the bottom only, but hot water radiation, has them joined along the top as well. This is quite essential to the proper circulation of the water. Steam radiation is always tapped for pipe connections at the bottom. Hot water rad- iation may have the flow connection enter at the top, and the return connection leave at the bottom, or may have both connections at the bottom. Hot water radiation can be heated very successfully with steam, but steam radia- tion cannot be used with hot water. 71. High versus JLow Radiators: In the adoption of a radiator height, the governing feature is usually the space allowed for the radiator. Thus, if a radiator of 26 inches in height requires so many sections as to become too long, then a 32 inch or a 38 inch section may be taken. In gen- eral, however, low radiators should be used as far as possible, for, with a high radiator, the air passing up along the sides of the sections becomes heated before reaching the top, and therefore, receives less heat from the upper half of the radiator, since the temperature difference here is small. Hence, the statement that low radiators are more efficient, that is, will transmit more B. t. u. per square foot per hour than will the high radiators. 86 HEATING AND VENTILATION 72. Effect of Condition of Radiator Surface on the Transmission of Heat: The efficiency of a radiator depends very largely upon the condition of its outer surface, a rough surface giving off very much more heat than a smooth surface. Painting, bronzing, shellacing or cover- ing the radiator in any manner affects the ability of the radiator to impart heat to the air circulating around it. Various tests bearing upon this question have been con- ducted, agreeing fairly well in general results. A series of tests conducted by Prof. Allen at the University of Michigan, indicated that the ordinary bronzes of copper, zinc or aluminum caused a reduction in the efficiency below that of the ordinary rough surface of the radiator of about 25 per cent., while white zinc paint and white enamel gave the greatest efficiency, being slightly above that of the original surface. Numerous coats of paint, even as high as twelve, seemed to affect the efficiency in no appreciable manner, it being the last or outer coat that always de- termined at what rate the radiator would transmit its heat. TABLE X. Dimensions and Surfaces of Radiators, per Section. si g "g Radiator Heights. Type of Radiator IS 1 = I *1 as 'H 45" 44" 38" 82" 26" 23" 22" 20" 18" 16" 14" 53 lOol. O. I 5 3 3 2% 2 1% 1% 2 Ool. O. I 8 8 5 4 8>i 2% 2% 2 8 Ool. O.I 9% 3 .... 6 5 4% 3K 3 2% 4 Ool O I. ,. -,/ QT/ 8 gi/ 5 4 8 19* 3 7 8 5 4 6 424 4 1 Ool Press . . 4 l s/ n I'K 1 X 2 Ool Press 2 4 2 Ji 9 3 Ool Press 2% 5M 4^ 94 1 Ool. Wall 1 Pressed 73. Amount of Surface Presented by Various Radiators: Table X, gives, according to the columns and heights, HOT WATER AND STEAM HEATING 87 the number of square feet of heating surface per section in cast and pressed radiators. This table will be found to present, in very compact form, the similar and much more extended tables in the various manufacturers' catalogs. An approximate rule supplementing this table and giving, to a very fa^r degree of accuracy, the square feet of aur- face in any standard radiator section, is as follows: mul- tiply the height of the section in inches by the number of columns and divide by the constant 20. The result is the square feet of radiating surface per section. The rule ap- plies with least accuracy to the one column radiators. 74. Hot Water Heaters: Heaters for supplying the hot water to a heating system may be divided into three classes: the round vertical, for comparatively small installations; the sectional, for plants of medium size; and the water tube or flre tube heater with brick setting for the larger in- stallations and for central station work. The round and sectional types usually have a ratio between grate and heating surface of 1 to 20, while the water tube or fire tube heater will have, as an average, 1 to 40. Many different arrangements of heating surface are in use to-day, every manufacturer having a product of particular merit. Trade catalogs supply the most up-to-date literature on this subject, but cuts of each of the types mentioned above may be found in Pig. 38. 75.. Steam Boilers: The products of many manufac- turers show but little difference between the hot water heater and the steam boiler. The latter is usually supplied with a somewhat larger dome to give greater steam stor- age capacity. For heating purposes, steam boilers fall into the same three classes as mentioned under water heat- ers, having about the same ratio of heating surface to grate surface. With the steam boiler generating steam at, say, 5 pounds gage, the temperature on one side of the heating surface is about 227 degrees, while in a water heater the temperature on the same side is about 180 degrees. Hence, with the same temperature of the burning gases, the tem- perature difference is greater in a water heater than in a boiler, resulting in a more rapid transfer of heat, and a correspondingly greater efficiency. 76. Combination Systems: What are known as com- bination systems are frequently used, principally the one HEATING AND VENTILATION which combines warm air heating with either steam or hot water. For such a system there is needed a combina- tion heater, as shown in Fig. 19. It consists essentially of a furnace for supplying warm air to some rooms, the down- stairs of a residence, for instance, and contains also a coil Fire Tube Type Fig. 38. HOT WATER AND STEAM HEATING 89 for furnishing hot water to radiators located in other rooms, say, on the upper floors, or in places where it would be difficult for air to be delivered. Considerable difficulty has been encountered in properly proportioning the heating sur- face of the furnace to that of the hot water heater, and the systems have not come into general use. 77. Fittings: Common and Special: Couplings, elbows and tees, especially for hot water work, should be so formed as to give a free and easy sweep to the contents. It is highly desirable in hot water work to use pipe bends of a radius of about five pipe diameters, instead of the common elbow. In either case all pipe ends should be carefully reamed of the cutting burr before assembling. This is most important, as the cutting burr is sometimes heavy enough to reduce the area of the pipe by one-half, thus creating serious eddy currents, especially at the elbows. If the single main hot water system be installed, great care should be used to plan the mains in the shortest and most direct routes, and the special fittings described and shown in Art. 64 should be used. What are known as eccentric reducing fittings are often of value in avoiding pockets in steam lines. Fig. 39 shows Fig. 39. types of these, which should always be used when, by re- duction or otherwise, a horizontal steam pipe would pre- sent a pocket for the collection of condensation with its re- sultant water hammer. Valves for either steam or hot water should be of the gate pattern rather than the globe pattern. The latter is objectionable in hot water systems because of the resistance offered the stream of water, due to the fact that the axis of the valve seat opening is perpendicular to the axis of the pipe connected. The globe valve is objectionable in a steam system because of the fact that in a horizontal run 90 HEATING AND VENTILATION of pipe it forms very readily a pocket for the collection of condensation, thus often producing a source of water hammer. In every way gate valves are preferable, for, as shown in Fig. 40, they present a free opening'without turns. The same caution applies in the use of check valves. Swing checks should al- ways be specified rather than lift checks, for the former offer much less re- sistance to the passage of the hot water, or the steam and condensation, as the case may be. P ig. 41 Fig. 40. shows a lift check and a swing check. To avoid the annoyance so often experienced by leaky packing around valve stems, there have been designed and Fig. 41. placed on the market various forms of packless valves. These are to be especially recommended for vacuum work, as the old style valve with its packed stem is, perhaps, the cause of more failures of vacuum systems than any other one item. Fig. 42 shows a section of this type of valve using the diaphragm as the flexible wall. All pack- less valves will be found to use a dia- phragm of -one form or another. Quick - opening Valves, or butterfly valves, are much used on hot water radi- ators; one quarter turn of the wheel or handle provided serves to open these full Fig. 42. and, when closed, they are so arranged that HOT WATER AND STEAM HEATING 91 a small hole through the valve permits just enough leakage to keep the radiator from freezing. Special radiator valves for steam are also to be obtained. Air valves have a most important function to discharge. As the air accumulates above the water or steam in the Fig. 43. radiators, its removal becomes absolutely necessary, if all of the radiating surface is to remain effectual. For this purpose small hand valves or pet cocks, Fig. 43, are in- serted near the top of the end section in all hot water work; and either these same valves or automatic ones are inserted for steam work. Valves are not as essential on two-pipe steam systems as on water or single-pipe steam systems, yet are generally used. For steam the air valve should be about one-third the radiator height from the top. Fig. 44 shows a common type of automatic air valve using the principle of the expansion stem. As long as the air flows around the stem and exhausts, the stem re- mains contracted, and the needle valve open; but when the hot steam enters and flows past the expansion stem, it lengthens sufficiently to close the needle valve. In other forms of air valves the heat of the steam closes the needle valve by the expansion of a volatile liquid in a small closed retainer. In still other forms the lower part of the valve casing is filled with water of condensation upon which floats an inverted cup, having air entrapped within. This cup carries the needle of the valve at its upper ex- tremity, the heat of the steam expanding the air sufficiently to raise the cup and close the valve. Where the system Is de- signed to act as a gravity installation, special air valves must be used which will not allow air to enter at any time. Fig. 92 HEATING AND VENTILATION 45 shows a type of automatic valve designed to accommo- date larger volumes of air with promptness, as when a long steam main or large trap is to be vented. This type employs a long cen- tral tube, as shown, which carries at the top the valve seat of the needle valve. The needle itself is carried by the two side rods. As long as the air flows up through the central pipe, the needle valve will remain open; but when hot steam enters the tube, it expands, and carries the valve seat up- ward against the needle, thus closing the valve. The size and strength of parts makes this form a very reliable one. The expansion tank, Fig. 46, for a hot wat- er system is often located in the bath room or closet near the bath room and its overflow connected to proper drainage. It should be at least 2 feet above the highest radiator. The connection to the heating system mains is most often by a branch from the nearest radiator riser, or it may have an independ- ent riser from the basement flow main. The capacity of the tank is usually taken at about one-twentieth of the volume of the entire system, or a more easily applied rule is to divide the total radiation by 40 to ob- tain the capacity of the tank in gallons. Fig. 45. See Table 33, Appendix. Figr. 46. CHAPTER VIII. HOT WATER AND STEAM HEATING. PRINCIPLES OF THE DESIGN, WITH APPLICATION. In a hot water or steam system, the first important item to be determined by calculation is the amount of radiation, in square feet, to be installed in each room. Nearly all other items, such as pipe sizes, boiler size, grate area, etc., are estimated with relation to this total radia- tion to be supplied. The correct determination, then, of the square feet of radiation in these systems is all-im- portant. 78. Calculation of Radiator Surface: Considering the standard room of Chapter III, where the heat loss was de- termined to be 14000 B. t. u. per hour on a zero day, the problem is, to find what amount of surface and what size of radiator will deliver to the room, under the conditions as given, just about 14000 B. t. u. per hour. Experiments by numerous careful investigators have shown that the ordin- ary cast iron radiator, located within the room and sur- rounded with comparatively still air, gives off heat,a,t the rate of 1.7 "B. t. u. (1.6 to 1.8, or 1.7 averag&) per tfegree difference between the temperature of the surrounding air and the average temperature of the heating medium, per hour. This is called the rate of transmission. With hot water the average conditions within the radiator have been found to be as follows: temperature of the water en- tering the radiator 180 degrees; leaving the radiator 160 degrees; hence, the average temperature at which the in- terior of the radiator is maintained is 170 degrees. Since, in this country, the standard room temperature is 70 de- grees, and, for hot water, the "degree difference" is 170 70 = 100, then a hot water radiator will give off under standard conditions 1.7 X 100 = 170 B. t. u. per hour. The temperature within a steam radiator carrying steam at pressures varying between 2 and 5 pounds gage is usually taken at 220 degrees, and the total transmission is approx- imately 1.7 X (220 70) = 255 B. t, u. per square foot per 94 HEATING AND VENTILATION hour. The general formula for the square feet of radiation, then, is R _ Total B. t. u. lost from the room per hour 1.7 (Temp. diff. between inside and outside of rad.) For hot water, direct radiation heating, this becomes, to the nearest thousandth H Rw = .006 H (30) 1.7 (170 70) For steam, direct radiation H R* = .004 H (31) 1.7 (220 70) It will be noticed from (30) and (31) that R w = 1.5 R B which accounts for the practice that some people have of finding all radiation as though it were steam, and then, when hot water radiation is desired, adding 50 per cent, to this amount. APPLICATION. From the standard room under considera- tion, formula 30 gives Rw .006 X 14000 = 84 square feet of radiator surface for hot water; and formula 31 gives R$ = .004 X 14000 = 56 square feet of radiator surface for steam. From these values the number of sections of a giv- en type of radiator can be determined by dividing by the area of one section, as explained in the preceding chapter. The length of the radiator may also be found from this same table, by noting the thickness of the sections, and multiplying by their number. Formulas 30 and 31 give the standard ratios be- tween the heat loss and direct radiation. If, however, the radiation is installed as direct-indirect, it is quite common practice to increase the amount of direct radiation by 25 per cent, to allow for the ventilation losses. On this basis formulas 30 and 31 become, respectively, Rw = .0075 H (32) R 8 = .005 H (33) Duct sizes for properly accommodating the air in direct- indirect heating may be taken from the following. To ob- tain the duct area in square inches, multiply the square feet of radiation by .75 to 1 for steam, and by .5 to .75 for hot water. To obtain the amount of air which may be expected to enter and pass through the radiator into the HOT WATER AND STEAM HEATING 95 room, multiply the square feet of radiation by 100 for steam, or by 75 for hot water. This gives the cubic feet of air entering per hour. Again, if the radiation is installed as purely indirect, yet not as a plenum system, it is common to increase the amount of direct radiation by 50 per cent. Now formulas 30 and 31 become, respectively, R w = .009 H (34)-a R a = .006 H (34)-b F or proportioning the duct sizes in indirect heating use the following table. To obtain the duct area in square inches, multiply the square feet of radiation installed by Steam Hot Water First Floor 1.5 to 2.0 1.0 to 1.33 Second Floor 1.0 to 1.25 .66 to .83 Other Floors .9 to 1.0 . 6 to .66 Vent ducts, where provided, are usually taken .8 of the area of supply ducts. Also, for finding the amount of air in cubic feet, which may be reasonably expected to enter under these conditions, Carpenter gives the following: Multiply the square feet of indirect radiation by Steam Hot Water First Foor 200 150 Second Floor 170 130 Other Floors 150 115 If this amount of air is insufficient for the desired degree of ventilation, more air must be brought in by correspond- ingly larger ducts, and for each 300 cubic feet additional with steam, or each 200 cubic feet additional with hot water, add one square foot to the radiation surface. A steam system may be installed to work at any pres- sure, from a vacuum of, say, 10 pounds absolute, to as high a pressure as 75 pounds absolute. To calculate the prop- er radiation for any of these conditions use formula 31 or its derivatives, and substitute the proper steam tempera- ture in place of 220 degrees. In like manner, to find the amount of hot water radi- ation for any other average temperatures of the water than the one given, merely substitute the desired average 96 HEATING AND VENTILATION temperature in the place of 170. One point should be re- membered, the maximum drop in temperature as the water passes through the heater will seldom be more than 20 degrees, even under severe conditions. More often it will be less, but this value is used in calculations. Again, the temperature of the entering water may be at the boiling point, if necessary, thus causing each square foot of sur- face to be more efficient and consequently reducing the to- tal radiation in the room. To illustrate, try formula 30 with a drop in temperature from 210 to 190 degrees and find 64 square feet of radiator surface for this room. Since a radiator always becomes less efficient from continued use, it is best to design a system with a lower temperature as given in the formula, and then, if necessary under stress of conditions, this system may be increased in capacity by increasing the water temperature, say, up to the boiling point. 79. Empirical Formulas: All of the above formulas may be considered as rational and checked by years of experience and application. Many empirical formulas have been de- vised in an attempt to simplify, but the results are always so untrustworthy that the rules are worthless unless used with that discretion which comes only after years of prac- tical experience. Many of these rules are based on the cubic feet of volume heated, without any other allowance, these being given anywhere from one square foot of steam surface per 30 cubic feet of space, to one square foot to 100 cubic feet. The extreme variation itself shows the un- reliableness of this method, and under no conditions should it be used for proportioning radiating surface. Various central heating companies, and others, proportion radia- tors for their plants according to their own formulas, among which the following may be noted. GWG G W C (a) Rw = 1- 1 R* = 1- h 2 10 60 2 10 200 2 (b) Rw = G + .05 W + .01 C R = (G + .05 W + .01 (?) (c) Rv> = .75 G + .10 W + .01 C Rs = .5 G + .05 W + .005 C It is evident that these are really simplified forms of Car- penter's original formula. When applied to the sitting room, where Carpenter's formula gave, for hot water and HOT WATER AND STEAM HEATING 97 steam, 84 square feet and 56 square feet, respectively, (a) gives 85.5 and 63, (b) gives 75 and 50, and (c) gives 82.5 and 46 respectively. Another approximate rule devised by John H. Mills and still used to some extent is "Allow 1 square foot of steam radiation for every 200 cubic feet of volume, 1 square foot for every 20 square feet of exposed wall and 1 square foot for every 2 square feet of exposed glass." Applying this to the standard room, it gives 9.75 -f- 13.25 + 18 = 41 square feet of steam radiation as against 56 square feet by rational formula. This shows a considerable difference from the rules preceding. 80. Greenhouse Radiation: The problem of properly proportioning greenhouse radiation is considered, by some of such special nature as to prohibit the use of theoretical formulas. The fact that the glass area is so large compared to the wall area and the volume, combined with the fact that the head of water in the system is small and that the radiation surface is usually built up as coils from 1&, 1% or 2 inch wrought iron pipe, gives rise to a problem that differs essentially from that of a room of ordinary construction. It is not surprising, therefore, to find a great variety of empir- ical formulas designed exclusively for this work. Whatever merit these may have, they do not give the assurance that comes from the application of rational formulas. It is always best to use rational formulas first and then check by the various empirical methods. Formulas 30 and 31, stated in Art. 78, when properly modified, are applicable to greenhouses and give very re- liable results. As stated above, the radiating surface Is usually that of wrought iron pipes hung below the flower benches or along the side walls below the glass. The trans- mission constant, K, for wrought iron or mild steel is 2.0 to 2.2 B. t. u. per square foot per degree difference per hour, making the total transmission per square foot of coil surface per hour about 2(170 70) = 200 for hot water, and 2(220 70) = 300 for steam. These values may be safely used. The only necessary modification of the two formulas men- tioned, consists in replacing the constant 1.7 by 2, giving for hot 98 HEATING AND VENTILATION = .005 H (3)-a 2(170 70) And for steam H R, = .0033 H (35)-b 2(220 703 If, however, the highest temperature at which it is desirable to maintain the house in zero weather is other than 70 de- grees, this temperature should be used instead of 70. In a greenhouse there is very little circulation of air, hence the heat loss. H, would be found from the equivalent glass area i. e., (G + .25 TF). Formula (35)-a and b would then reduce to R w = .35 (G + .25 TF) and R s = .23 (G + .25 TF). Because of the fact that the heat loss through the wall is very small compared to that through the glass, some per- sons prefer to drop the last term entirely. If this is done the simple relations, R w = .35 G, and R a .23 G, will be obtained for a greenhouse of maximum temperature of 70 degrees. It is noticed that these values give about one square foot of H. TF. radiation to three square feet of glass area, and one square foot of steam radiation to five square feet of glass area as approximate rules. These figures should be considered a minimum. Empirical rules for greenhouse radiation, quoted by many firms dealing in the apparatus, are usually given in the terms of the number of square feet of glass surface heated by one lineal foot of 1% inch pipe. A very commonly quoted and accepted rule is, one foot of 1% inch pipe to every 2^4 square feet of glass, for steam; or, one foot of 1% inch pipe to every 1% square feet of glass, for hot water, v\hen the interior of the house is 70 degrees in zero weather. The following table, from the Model Boiler Manual, shows the amount of surface for different interior temperatures and different temperatures of the heating medium. In general, it may be said that in greenhouse heating, great care should be used in the rating and the selection HOT WATER AND STEAM HEATING of the boilers or heaters. It is well to remember that the severe service demanded by a sudden change in the weather is much more difficult to meet in greenhouses than in ordin- ary structures, and that a liberal reserve in boiler capacity is highly desirable. TABLE XI. s |M !! H 400 450 50 550 600 (55 70 75 800 85 Temperature of Water in Heating Pipes Steam 140 1600 1800 2000 Three Ibs. Pressure Square feet of glass and its equivalent proportioned to one square foot of surface in heating pipes or radiator 4.33 8.63 8.07 gKfr.98 2.19 1.86 1.58 1.37 1.16 .99 5.25 4.65 3.92 3-89 2-89 2.53 2.19 1.92 1.63 1.42 6-66 5-55 4-76 4.16 8.63 3.22 2.81 2-5 2.17 1.92 7.69 6.66 5.71 5. 4.83 3.84 8-44 3.07 2.78 2.46 8. 7-5 7. 6.5 6. 5.5 5. 4.5 4. 3.5 This table is computed for zero weather; for lower temperatures add iy a per cent, for each degree below zero. 81. The Determination of Pipe Sizes: The theoretical determination of pipe sizes in hot water and steam systems has always been more or less unsatisfactory, first, because of the complicated nature of the problem when all points having a bearing upon the subject are considered, and second, because it is almost an impossibility to even ap- proximate the friction offered by different combinations and conditions of piping. The following rather brief analysis gives a theoretical method for determining pipe sizes where friction is not considered. In a hot water system let the temperatures of the water entering and leaving the radiator be, respectively, 180 and 160 degrees; then it is evident that one pound of the water in passing through the radiator, gives off 20 B. t. u. Under these conditions the standard room would have 14000 -f- 20 = 700 pounds of water passing through the radiator per hour. Converting this to gallons, it is found to be 84.03. But the radiation for this room was found to be 84 square feet. Whence, it may be said that a hot water radiator 100 ^ HEATING AND VENTILATION under normal conditions of installation and under heavy service requires one gallon of water per square foot of sur- face per hour. Knowing the theoretical amount of water per hour, it remains only to obtain the theoretical speed at which it travels, due to unbalanced columns, to obtain finally, by division, the theoretical area of the pipe. Consider a radiator to be about 10 feet above the source of heat, and the temperature in the flow riser to be 180 degrees and in the return riser 160 degrees, good values in practice. Now, the heated water in the -flow riser weighs 60.5567 pounds per cubic foot, while that in the return riser weighs 60.9697 pounds per cubic foot. The mo- / W W \ tive force is f = g [ ) where g is the acceleration \ w + wJ due to gravity, W is the specific gravity (weight) of the cooler column and W is the specific gravity (weight) of the warmer column. Substitute / for g in the velocity formula and obtain v = fafh and / / W W \ v =-/ 2gh( ) (36) \ \W + W / Inserting values W, W and assuming h = 10 feet, we have v = V2 X 32.2 X 10 X .0034 = V 2 -1896 = 1.47 feet per second. From this, it has become a custom to speak of 1.5 feet per second or 5400 feet per hour, as the theoretical velocity of water in, say, a first floor riser, disregarding the effect of all friction and horizontal connections. Theoretical veloci- ties for any other height of column and for other temper- atures may be obtained in like manner. Continuing this special investigation and changing the 84 gallons per hour to cubic inches per hour by multiplying by 231, the internal pipe area may be obtained by dividing by the unit speed per hour which gives (84 X 231) + (5400 X 12) = .3 square inch. This corresponds to approximately a % inch pipe and without doubt, would supply the radiator if the sup- position of no frictional resistances could be realized. This ideal condition, of course, cannot be had, nor can the fric- tion in the average house heating plant be theoretically treated with any degree of satisfaction. Hence it is still the custom to use tables for the selection of pipe sizes, HOT WATER AND STEAM HEATING 101 based upon what experience has shown to be good practice. Such tables, from various authorities, may be found in the Appendix. It is safe to say that one should never use any- thing- smaller than a 1 inch pipe in low pressure hot water work. With steam systems, where the heating medium is a vapor, and subject in a lesser degree to friction, the discrepancy between the theoretical and the practical sizes of a pipe is not so great as in hot water. Each pound of steam, in condensing, gives off approximately 1154 181 = 973 B. t. u. To supply the heat loss of the standard room, 14000 B. t. u. per hour, it would require 14.5 pounds of steam per hour. When it is remembered that the calculated surface of the direct steam radiator for this room was 56 square feet, it appears that a radiator, under stated conditions and under a heavy service, requires one-fourth of a pound of steam per square foot of surface per hour. This may be shown in another way: each square foot of steam radiation gives off 255 B. t. u. per hour; then, each square foot will condense 255 -j- 973 =: .26 + pounds of steam per hour. Now the volume of the steam per pound at the usual steam heating pressure, 18 pounds absolute, is 21.17 cubic feet. Since the standard room radiator required 14.5 pounds per hour, it would, in that time, condense steam corres- ponding to a void of 21.17 X 14.5 307 cubic feet per hour. This is the volume of the steam required by the radiator, and, if the speed of the steam in the pipe lines be taken at 15 feet per second, or 54000 feet per hour, the area of the pipe would be 307 X 144 -7- 54000, or .82 square inch, corresponding very closely to a 1 inch pipe. For a two- pipe system this would be considered good practice under average conditions; but in a one-pipe system, where the condensation is returned against the steam in the same pipe that feeds, a pipe one size larger would be taken. Table 33, Appendix, calculated from Unwin's formula, may be used in finding sizes and capacities of pipes carrying steam. In addition to this, Tables 26, 27, 28 and 29 give sizes that are recommended by experienced users. For a theoretical discussion of loss of head by friction in hot water and steam pipes, see Arts. 144 and 172. 82. Grate Area: To obtain the grate area for a direct radiation hot water or steam system by the B. t. u. method, 102 HEATING AND VENTILATION the same analysis as found in Chapter IV, may be applied. The total B. t. u. heat loss, H, is that calculated by the formula and does not include Hv, the heat loss due to ven- tilation, since with the direct hot water or steam system as usually installed no ventilation is provided. In any special case where ventilation is provided in excess, use E r instead of H. The commercial rating of heaters and boilers is a subject each day receiving greater attention at the hands of manufacturers; yet it is a subject where much uncer- tainty is felt to exist. Hence the recommendation, "Always check grate area by an actual calculation," rather than rely entirely upon the catalog ratings. 83. Pitch of Mains: The pitch of the mains is quite as important in hot water as in steam work. This should not be less than 1 inch in 10 feet for hot water systems, and not less than 1 inch in 30 feet for steam systems. Greater pitches than these are desirable, but not always practic- able. In hot water plants the pitch of the basement mains, whether flow or return, is upward as these mains extend from the source of heat, that is, the highest point is the farthest from the heater. In steam plants the mains, under any condition of arrangement, always pitch downward in the direction of the flow of the condensation. 84. Location and Connection of Radiators: In locat- ing radiators, it is best to place them along the outside or the exposed walls. When allowable, under the windows seems to be a favorite position. Especially in buildings of several stories, the radiators should be arranged, where possible, in tiers, one vertically above another, thus re- ducing the number of and avoiding the offsets in the risers. In the one-pipe system any number of radiators may be con- nected to the same riser. In the two-pipe system several radiators may have either a common flow riser, or a common return riser, but should never have both, either with hot water or with steam. The connections from the risers to the radiators should be slightly pitched for drainage and are usually run along the ceiling below the radiator connected. These connections should be at least two feet long to give that flexibility of connection to the radiator made necessary by the expan- HOT WATER AND STEAM HEATING 103 sion and contraction of the long riser. Similarly, all risers should be connected to the mains in the basement by hori- zontals of about two feet to allow for the expansion and contraction of the mains. A system thus flexibly connected stands in much less danger of developing leaky joints than does one not so connected. For sizes of radiator connections see Table 24, Appendix. 85. General Application: Figs. 48, 49 and 50 show the typical layout of a hot water plant. Due to the similarity be- tween hot water and steam installations, the former only will be designed complete. In attempting the layout of such a system, the very first thing to be done is to decide at what points in the rooms the radiators should be placed. This should be done in conjunction with the owner as he may have particular uses for certain spaces from which radia- tors are hence excluded. The first actual calculation should be the heat loss from each room, with the proper exposure losses, and the results should be tabulated as the first column of a table similar to Table XII. In the example here given, this loss is the same as, and taken from, the table of computations for the furnace work, Art. 48, the house plans being identical. The second column of Table XII, as indicated, is the square feet of radiation; and since this is a hot water, direct radiation system, it is obtained by taking .006 of the items in the first column according to formula 30. Knowing this, a type and height of radiator can be selected, and the number of sections determined by Table X. Next obtain the lengths of radiators by multiplying the number of sections by the total thickness of the sections, as given in Table X, and determine whether or not the radiator of such a length will fit into the chosen space. If not, then a radiator of greater height and larger surface per section must be selected. Riser sizes and connections may be taken ac- cording to Tables 26 and 24 respectively. The column of Table XII headed "Radiators Installed" gives first the num- ber of sections; second, the height in inches; and third, the number of columns or type of the section. Locate radiators on the second floor and transfer the location of their riser positions to first floor plan, then to the basement plan. Locate radiators on the first floor and 104 HEATING AND VENTILATION transfer their riser locations to the basement plan, which will then show, by small circles, the points at which all risers start upward. This arrangement will aid greatly in the planning of the basement mains. The keynotes in the layout of the basement mains should be simplicity and directness. If the riser positions show approximately an even distribution all around the basement, it may be advisable to run the mains in complete circuits around the basement. If, again, the riser positions show aggregation at two or three localities, then two or three mains running directly to these localities would be most desirable. As an example, take the applica- tion shown here. The basement plan shows three clusters of riser ends, one under the kitchen, another under the study, and a third on the west side of the house. This condition immediately suggests three principal mains, as shown. The main toward the kitchen supplies the bath, chamber 4 and the kitchen, making a total of 131 square feet. Being only about 13 feet long, it would readily carry this radiation if of 2 inch diameter. See Table 29. The main to the study and the hall supplies chamber 1, the hall and the study, making a total of 221 square feet, which can be carried by a 2% inch pipe. The main to the west side of the house supplies chamber 2, chamber 3, the sitting room and the dining room, a total of 249 square feet, which would almost require a 3 inch main, according to the table, were it not for its comparatively short length. A 2^ inch pipe would amply supply this condition. In hot water work, as well as in steam, it is customary to take the connections to flow risers from the top of the mains, thus aiding the natural circulation, Fig. 31. If not taken directly from the top of the main, it is often taken at about 45 degrees from the top. This arrangement, with a short nipple, a 45 degree elbow, and the horizontal connec- tion about 1% to 2 feet long, makes a joint of sufficient flexibility between the main and riser to avoid expansion troubles. In the selection of a heater or boiler much that has been said concerning furnaces applies. The heater or boiler should, above all, have ample grate area, checked on a B. t. u. basis, and should have a sufficient heating surface so HOT WATER AND STEAM HEATING 105 designed that the heated gases from the fire impinge per- pendicularly upon it as often as may be without seriously reducing the draft. As shown by the total of the radiation column, a hot water boiler should be selected of such rated mains and risers. Since this loss is usually taken from 20 to 30 per cent., depending upon the thoroughness with which the basement mains are insulated, the heater for this house should have a rated capacity of not less than 720 square feet of radiation. TABLE XII. | 1* Radiators installed Lengths ofRad'or installed Riser Sizes II o"S *- *-* g "0 d tsS \\ 1 g 1 is s il hS & 3 * S o "S3 *a ffii: & o ^ c rt Sitting R 14000 84 15-82-3 14-44-3 34 42 1* i^ 1 Dining R. 10800 65 14-26-3 18-26-3 32 54 1% 1J4 IK Study 13250 80 82-14-3 20-14-P 72 60 1V4 1% Kitchen 11900 70 12-82-3 8 -45-4 24 1H 1H l>i Rec'p'n Hall 14000 84 15-82-3 14-44-8 84 42 i^ 1V4 Chamber 1 9400 57 18-26-3 16-26-3 30 48 iM IK IX Chamber 2 9850 60 13-26-3 16-26-3 30 48 1% 1M IX Chambers 6600 40 10-26-3 12-26-3 23 36 i 1 1 Chamber 4 5600 35 10-26-3 12-26-8 28 36 i 1 1 Bath... 4400 6-26-3 7-26-3 14 21 j 1 j "I leoi 166 HEATING AND VENTILATION. 4Lr *JL_t ttfia-Zft- I --- L, 15' 9i" - ifjl^'j. - 9' - Sir - ---- ** ^ J PLAM Ceiling 6 ' Fig. 48. HOT WATER AND STEAM HEATING 107 fipoR. PLAN Ceiling /O ' Fig. 49. 108 HEATING AND VENTILATION 5ttohD riPOR. PLAN Ceiling $' , Fig. 60. HOT WATER AND STEAM HEATING 109 86. Insulating: Steam Pipes: In all heating systems, pipes carrying steam or water should be insulated to protect from heat losses, unless these pipes are to serve as radiating surfaces. In a large number of plants the heat lost through these unprotected surfaces, if saved, would soon pay for first class insulation. The heat transmitted to still air through one square foot of the average wrought iron pipe is from 2 to 2.2 B. t. u. per degree difference of temperature between the inside and the outside of the pipe. Assuming the minimum value, and also that the pipe is fairly well protected from air currents, the heat loss is, with steam at 100 pounds gage and 80 degrees temperature of the air, (338 80) X 2 = 516 B. t. u. per hour. With steam at 50, 25, and 10 pounds gage respectively this will be 436, 374 and 320 B. t. u. If the pipe were located in moving air, this loss would be much increased. It is safe to say that the average low pressure steam pipe, when unprotected, will lose be- tween 350 and 400 B. t. u. per hour. Taking the average of these two values and applying it to a six inch pipe 100 feet in length, for a period of 240 days at 20 hours a day, we have a heat loss of 171 X 375 X 240 X 20 = 307800000 B. t. u. With coal at 13000 B. t. u. per pound and a furnace efficiency of 60 per cent, this will be equivalent to 39461 pounds of coal, which at $2.00 per ton will amount to $39.46. From tests that have been run on the best grades of pipe insulation, it is shown that 80 to 85 per cent, of this heat loss could be saved. Taking the lower value we would have a financial saving of $31.56 where the covering is used. Now if a good grade of pipe covering, installed on the pipe, is worth $35.00, the saving in one year's time would nearly pay for the covering. To be effective, insulation should be porous but should be protected from air circulation. Small voids filled with still air make the best insulating material. Hence, hair felt, mineral wool, eiderdown and other loosely woven ma- terials are very efficient. Some of these materials, however, disintegrate after a time and fall to the bottom of the pipe, leaving the upper part of the pipe comparatively free. Many patented coverings have good insulating qualities as well as permanency. Most patented coverings are one inch in thick- ness and may or may not fit closely to the pipe. A good ar- 110 HEATING AND VENTILATION rangement is to select a covering one size larger than the pipe and set this off from the pipe by spacer rings. This air space between the pipe and the patented covering is a good insulator in itself. Table 35, Appendix, gives the results of a series of experiments on pipe covering, obtained at Cornell University under the direction of Professor Car- penter. These values are probably as nearly standard as may be had. 87. "Water Hammer: When steam is admitted to a cold pipe, or to a pipe that is full of water, it is suddenly con- densed and causes a sharp cracking noise, that under certain conditions may become so severe as to crack the fittings and open up the joints. The noise is produced by the sudden rush of water in an endeavor to fill the vacuum produced by the condensed steam. Steam at atmospheric pressure occupies 1644 times the volume of the water that produced it, hence, by suddenly condensing it, a very high vacuum may be produced. This action causes a relatively high velocity in any body of water adjacent to it. The worst condition is found when a quantity of steam enters a pipe filled with water. Condensation suddenly takes place and the two bodies of water come together with high velocity causing severe concussion. Steam should always be admitted to a cold pipe, or to one filled with water, very slowly. 88. Returning the Water of Condensation, in a Low Pressure Steam Heating System, to the Boiler: In re- Eig. 51. Fig. 52. turning the water of condensation to the boiler four methods are in use; gravity, steam traps, steam loops and steam pumps. The gravity system is the simplest and is used in all cases where the radiation is above the level of the boiler and HOT WATER AND STEAM HEATING 111 where the boiler pressure is used in the mains. In a gravity return, no special valves or httings are necessary, but a free path with the least amount of friction in it is provided be- tween the radiators and a point on the boiler below the water line. No traps of any kind should be placed in this return circuit. When the radiation is below the water line, or where the pressure in the mains is less than that in the boiler, some form of steam-trap must be put in with special provision for returning this water to the boiler. Two kinds of traps may be had, low pressure and high pressure. The first is well represented by the bucket trap, Fig. 51, and the second, by the Bundy trap, Fig. 52. The action of these traps is as follows: Bucket trap. Water enters at D and collects around the bucket, which is buoyed up against the valve. The water collects and overflows the bucket until the com- bined weight of the water and bucket overbalances the buoyancy of the water. The bucket then drops and the steam pressure upon the inside, acting upon the surface of the water, forces it out through the valve and central stem to the outlet B. When a certain amount of this water has been ejected, the bucket again rises and closes the valve. This action is continuous. Bundy trap. Water enters at D through the central stem and collects in the bowl A, which is held in its upper position by a balanced weight. When the water collects in the bowl sufficiently to lift the weight, the bowl drops, the valve E opens, and steam is admitted to the bowl, thus forcing the water out through the curved pipe and the valve E. This action is continuous. Each trap is capable of lifting the water approximately 2.4 feet for each pound of differential pressure. Thus, for a pressure of 5 pounds gage within the boiler and 2 pounds gage on the return, the water may be lifted 7 feet above the trap, or say, to the top of an ordinary boiler. This is not sufficient, however, to admit the water into the boiler against the pressure of the steam. A receiver should be placed here to catch the water from the separating trap and deliver it to a second trap above the boiler which, in turn, feeds the boiler. Live steam is piped from the boiler to each trap, but the steam supply to the lower trap is 112 HEATING AND VENTILATION throttled, to give only enough pressure to lift the water into the receiver. A system connected up in this way is shown in Fig. 53. Traps which receive the water of condensation for the pur- pose of feeding the boiler are called return traps and sometimes work under a higher pressure' of steam than the separating traps. Many different kinds of traps are in general use but these will illustrate the principle of returning the condensation to the boiler. A very simple arrangement, and yet a very difficult one to operate satisfactorily, is by the use of the steam loop, Fig. 54. The water of condensation from the radiators drains to the receiver A, which is in direct communication with the riser B. The drop leg D, being in communication with the boiler through a check valve which opens toward the boiler at the lowest point, is filled with water to the point X, suffi- ciently high above the water line of the boiler that the static head balances the differential pressure between the steam in the boiler and that in the condenser. The horizon- tal run of pipe C serves as a condenser and, in producing a partial vacuum, lifts the water from the receiver. This water is not lifted as a solid body, but as slugs of water interspersed with quantities of steam and vapor. The water in A is at or near the boiling point and the reduced pressure in B reevaporates a portion of it which, in rising as a vapor, assists in carrying the rest of the water over the goose-neck. When the condensation in D rises above the point X, the static pressure overbalances the differential steam pressure, and water is fed to the boiler through the check. To find the location of the point X, above the water line in the boiler, the following will illustrate: Let the pres- sures in the boiler, condenser and receiver be respectively HOT WATER AND STEAM HEATING 113 5, 2 and 4 pounds gage, then the differential pressure between the boiler and condenser is 3 pounds per square inch. If the weight of one cubic foot of water at 212 degrees is 59.76 pounds, then the pressure is .42 pounds per square inch for each foot in height. Stated in other words, one pound dif- ferential pressure will sustain 2.4 feet of water. With a pressure difference of 3 pounds,, this gives 3 -r- .42 = 7.2 feet from the water level in the boiler to the point X, not taking into account the friction of the piping and check which would vary from 10 to 30 per cent. Assuming this friction to be 20 per cent, we have, 7.2 -^ .80 = 9 feet of head to produce motion of the water. Fig. 54. The length of the riser pipe B and its diameter, depend upon the differential pressure between the condenser and the receiver, and upon the rapidity of condensation in the horizontal. With a differential pressure of 2 pounds this would sus- pend 2X2.4 = 4.8 feet of solid water. The specific gravity, however, of the mixture in this pipe is much less than that of solid water. For the sake of argument let this specific 114 HEATING AND VENTILATION gravity be 20 per cent, of that of solid water, then we would have a possible lift, not including friction, of 5 X 4.8 = 24 feet. This is 24 9 = 15 feet below the water level in the boiler. The diameter of the riser may vary for different plants, but for any given plant the range of diameters is very limited. These, as has been stated, are usually found by experiment. A drain cock should be placed in the receiver at the lowest point. When cold water has collected in the re- ceiver it is necessary to drain this water to the sewer before the loop will work. An air valve should be placed at the top of the goose-neck to draw off the air. If the horizontal pipe is filled with air, there will be no condensation and the loop will refuse to work. Never connect a steam loop to a boiler in connection with a pump or any other boiler feeder. To determine whether a loop is working or not, place the hand on the horizontal' pipe. If this is cold it is not working. The last method mentioned for feeding condensation to the boiler was by the use of a steam pump. This is fully dis- cussed in Art. 161. 89. Suggestions for Operating Hot Water Heaters and Steam Boilers: Before firing up in the morning, examine the pressure gage to see if the system is full of water. If there be any doubt, inspect the water level in the expan- sion tank. If it is a steam system, examine the gage glass and try the cocks to see if there is sufficient water in the boiler. See that all valves on the water lines are open. On the steam system try the safety valve to see if it is loose and see if the pressure gage stands at zero. Clean the fire and sprinkle over it a small amount of fresh coal. Open up the drafts and when the fire is burning well fill up with coal. In starting a fire under a cold boiler it should not be forced, but should warm up gradually. Hard coal may be thrown evenly over the fire. Soft coal should be banked in front on the grate, until the gases are driven off. It is then distributed back over the fire. The thickness of the fire will vary from four inches to one foot depending upon the draft and the kind of coal. HOT WATER AND STEAM HEATING 115 Clean the fire when it has burned low, partially closing the drafts while cleaning:. In a boiler or heater, using the water over continuously, there will be little need of cleaning out the inside. In a system using fresh water continuously, however, the boiler should be blown off and cleaned about once or twice a month. Never blow off a boiler while hot or under heavy pressure. In every system the heater or boiler should be thoroughly overhauled and cleaned before firing up in the fall. Keep the ash pit clean and protect the grates from burn- ing out. Keep the tubes and gas passages clean and free from soot. Inspect the pressure gage, glass gage, water cocks and thermometers frequently. In case of low water in a steam system, cover the fire with wet ashes or coal and close all the drafts. Do not open the safety valve. Do not feed water to the boiler. Do not draw the fire. Keep the conditions such as to avoid any sudden shock. After the steam pressure has dropped, draw the fire. Excessive pressure may be caused by the sticking of the safety valve in the steam system, or by the stoppage of the water line to the expansion tank in the hot water system. The safety valve should never be allowed to lime up, and the expansion tank should always be open to the heater and to the overflow. When leaving the fires for the night, push them to the rear of the grate and bank them as stated in Art. 59. References on Hot Water and Steam. TECHNICAL BOOKS. Snow, Principles of Heat., Chap. IX, X, I. C. S., Prin. of Heat, and Vent. p. 1185, 1091. Monroe, Steam Heat. & Vent., p. 13. Law- ler, Hot Water Heating, p. 19. Carpenter, Heat. & Vent. Bldgs., p. 150, 231. Thompson, House Heat, ty (steam & Water, p. 15. Hubbard Power, Heat. & Vent., pages 433, 464, 484, 505, 510. TECHNICAL PERIODICALS. Engineering News. Suggestions for Ehx'st Steam Heat, Apr. 7, 1904, p. 332. An Improved Steam Heat. System, Thermo- grade System, July 23, 1903, p. 80. Factory System of the United Shoe Machinery Co., W. C. Snow, May 25, 1905, p. 537. Heating a Trolley Car Barn, J. I. Brewer, April 29, 1909, p. 462. Engineering Review. Heat. & Vent, of the new Parental Home and School at Flushing, L. L, Jan. 1910, p. 48. A Hot Water System with Radiators and Boiler on the same Level, J. P. Lisk, Aug. 1908, p. 34. A Hot Water Heat. System for a City Residence, J. P. LLsk, June 1909, p. 44. Hot Water Heat. Apparatus in Plymouth Church, Brooklyn, N. Y., Dec. 1908, p. 19. Heat., Vent, and Temperature Regulation in the 116 HEATING AND VENTILATION Measles Pavilion of the Kingston Ave. Hospital, Brooklyn, N. Y., Jan. 1910, p. 35. Heat, and Vent. Plant of the Boston Safe Deposit and Trust Company's Building, C. L. Hubbard, April 1910, p. 37. Heat, and Vent. Installation in the Burnet St. School, Newark, N. J., Jan. 1909, p. 20. A Unique Low Pressure Steam Heat. Apparatus, Feb. 1909, p. 38. Practical Points on Steam Heating (Direct Heating), C. L. Hubbard, Aug. 1908, p. 29. (Indirect Heat.), Sept. 1908, p. 19. (Exhaust Steam Heat.), Nov. 1908, p. 21. Steam Heating Systems, Wm. J. Baldwin, March 1905, p. 7. Machinery. Shop Heating by Direct Radiation, C. L. Hubbard, July 1910, p. 884. Sizes of Pipe Mains for Hot Water Heating, C. L. Hubbard, Sept. 1909, p. 38. The Railway Review. Heating System of the Scranton St. Rail- way Shops, June 13, 1908, p. 480. Heating of Passenger Trains May 23, 1908, p. 408. The Pennsylvania R. R. System of Heat, and Vent. Passenger Trains, Feb. 22, 1908, p. 157. Vent, and Heating of Coaches and Sleeping Cars, July 18, 1908, p. 586. Hot Water Heating Arrangements for Passenger Stations, Oct. 10, 1908, p. 829. Typical Heating Plants, Horace L. Winslow Co., June 18, 1910, p. 596. The Heating & Ventilating Magazine. Res- idence Heating by Direct and Indirect Hot Water, July, 1905, p. 25. Carrying Capacities of Pipes in Low Pressure Steam Heating, Wm. Kent, E eb. 1907, p. 7. Standard Sizes of Steam Pipes, Jas. A. Donnelly, Jan. 1907, p. 21. Formula for Pipe Sizes in Hot Water Heating, Oliver H. Schlemmer, Sept. 1907, p. 9. Co-efficient of Transmission in Cast Iron Radiation, John R. Allen, Aug. 1908, p. 19. Relative Capacities of Pipes, John Jaeger, May 1907, p. 1. Methods of Figuring Radiation, Gerard W. Stanton, Dec. 1907. Computation of Radiating Sur- face, J. Byers Holbrook, Nov. 1904, p. 77. Domestic Engineering . A Practical Manual of Steam and Water Heating. E. R. Pierce, CSeries of Articles), Vol. 51, No. 2, April 9, 1910; Vol. 53, No. 9, Nov. 26, 1910. Proportions and Power of Low Pressure Heating Boilers, Vol. 47, No. 11, June 12, 1909, p. 319. How to Install and Cover a Steam or Hot Water Main, "Phoenix," Vol. 46, No. 10, March 6, 1909, p. 278. How to Secure Correct Pipe Sizes for Low Pressure Steam Heating, E. K. Munroe, Vol. 45, No. 9, Nov. 28, 1908, p. 243. Rules for Proportioning Indirect Heating Plants, R. T. Crane, Vol. 49, No. 6, Nov. 6, 1909, p. 143. Trans. A. #. H. & V. E. Circulation of Hot Water, J. S. Brennan, Vol. XI, p. 93. Residence Heating by Direct and Indirect Hot Water, E. F. Capron, Vol. XI, p. 174. Standard Sizes of Steam Mains, J. A. Donnelly, Vol. XIII, p. 43. The Carrying Capacity of Pipes in Low Pressure Steam Heating, Wm. Kent, Vol. XIII, p. 54. Heating and Ventilating a Group of Public Schools, S. R. Lewis, Vol. XIII, p. 187. The Com- bined Pressure and Vacuum Systems of Steam Heating, G. Hoffman, Vol. XIII, p. 223. Sizes of Return Pipes in Steam Heating Apparatus, J. A. Donnelly, Vol. XII, p. 109. Pro- portioning Hot Water Radiation in Combination Systems of Hot Water and Hot Air Heating, R. C. Carpenter, Vol. VII, p. 132. Tests of Radiators with Superheated Steam, R. C. Carpenter, Vol. VII, p. 185. Relative Economy of Steam, Vapor, Vacuum and Hot Water Heating for Residences, Vol. XII, p. 341. The Relation between the Completeness of Air Removal and the Efficiency of Steam Radiators, Vol. XII, p. 315. Advantage of Low Pressure Hot Water Heating Sys- tems, Vol. XI, p. 183, 209. Measurements of Wall Radiators, Vol. XII, p. 361. Advantages of Standard Dimensions of Radiator Valves and Connections, Vol. XIII, p. 148. The Relative Healthfulness of Direct and Indirect Heating Sys- tems, Vol. XIII, p. 36. Improving the Heating Capacity of a Radiator by an Electric Fan, Vol. VIII, p. 222. CHAPTER IX. MECHANICAL, WARM AIR HEATING AND VENTILATING SYSTEMS. DESCRIPTION OF SYSTEMS AND APPARATUS EMPLOYED. 90. Fire-places, Stoves, Furnaces and Direct Radiation Systems of both steam and hot water have, individually, advantages and disadvantages, but, in common, all lack what is increasingly being considered as of more import- ance than heating, namely, positive ventilation. Merely to heat a poorly ventilated apartment only serves to increase the discomfort of the occupants, and modern legislative bodies are reflecting the opinion of the times by the passage of compulsory ventilation laws affecting buildings with numerous occupants, such as factories, barracks, school houses, hotels and auditoriums. To meet this demand for the positive ventilation of such classes of buildings, there has been developed what is variously known as the hot Mast heating system, plenum system, fan Wast system or mechanical warm air system. 91. Elements of the Mechanical Warm Air System: Known by whatever name, this system contemplates the use of three distinctly vital elements; first, some form of hot metallic surface over which the forced air may pass and be heated; second, a blower or fan of some description to propel the air; and third, a proper arrangement of ducts or passageways to distribute this heated air to desired locations. P igs. 66 and 67 show these essentials, fan, heating coils and ducts in their relative positions with con- nections as found in a typical plant of this system. Many attachments and improved mechanisms may be had to-day in connection with this system, such as air washers and humidifiers, automatic damper control systems, and brine cooling systems whereby the heating coils may be used as cooling coils, and, during hot weather, be made to maintain the temperature within the building from 10 de- 118 HEATING AND VENTILATION grees to 15 degrees lower than the atmosphere. Any of these auxiliaries, however, change in no way the necessity for the three fundamentals named and their general ar- rangement as shown. 92. Variations in the Design ~f Mechanical Warm Air Systems: With regard to the position of the fan, two methods of installing the system are common. The first and most used is that snown by Fig. (55), a, where the fan Is in the basement of the building and forces the air by pressure upward through the ducts and into the rooms. This causes the air within the entire building to be at a ! / Fig. Diagram of Plenum System. b. Diagram of Exhaust System. pressure very slightly higher than the atmosphere, and hence all leakages will be outward through doors and win- dow crevices. A system so instaPed is usually called a plenum system. The fan may, however, be of the exhausting type, Fig. (55), b, and placed in the attic with which ducts from the rooms connect, so that the fan tends to keep the air of the building at a slight vacuum as compared with the atmosphere, thus inducing ventilation. Air is then PLENUM WARM ATR HEATING 119 supposed to enter the basement inlet, pass over the coil surface, and, when heated, pass to the various rooms through the ducts provided. But air from the atmosphere will just as readily leak in at windows or other crevices, as to come in over the heaters, and then the system will fail in its heating work. B or this reason the exhaust heating system, as it is usually known, is seldom installed, except where aid in the prompt removal of malodors is desired. Combined plenum and exhaust systems are to be recom- mended wherever the expense can be justified. 93. Blowers and Fans: Many methods of moving air for ventilating and heating purposes have been devised, some positive at all times, others so dependent upon the ex- istence of certain conditions as to be a constant source of trouble. It is coming to be a very generally accepted fact, that if air is to be delivered at definite times, in definite quantities and in definite places, it must be force^. there, and not merely allowed to go under conditions readily changing or disappearing. The recognition of this fact has led to a very common use of the mechanical fan or blower for im- pelling air, and this use has, in turn, caused the develop- ment of fans and blowers to a fairly high degree of efficiency. 120 HEATING AND VENTILATION By the aid of the mechanical apparatus, air may be moved positively in either of two ways, by the exhaust method and by the plenum method, each having developed fans best suited to its needs. In the exhaust method the fan is corn- Fig. 57. monly of the disk or propellor blade type, shown in Fig. 56 or 57, is usually installed in the attic or near the top of the building, although with a system of return ducts it may be installed in the basement, and moves the air by suction. Tue plenum system uses a fan of the paddle wheel type, shown in Bigs. 58 and 59; the first is the standard form of fan wheel in common use, and the second is a more recent development of the same, called the "turbine" fan wheel, shown direct connected to a De Laval steam turbine. Tne wheels of the fans are also shown. Tests of the latter wheel seem to show a somewhat higher efficiency than has heretofore been possible with the older forms. Both of these forms of fans are used in plenum work, and are placed on the forcing side of the circulating system just between the air Intake and the heater coils, or just follow- ing the heater coils, and hence produce a pressure within the building or suite heated, so that leakages are outward and not so detrimental to the good working of the plant as in the exhaust system. PLENUM WARM AIR HEATING 121 The motive power for fans may be of four kinds, electric direct drive, steam engine or steam turbine direct drive, and belt and pulley drive, as shown in Figs. 57, 58, 59 Fig". 58. Fig. 59. and 60. Which of these drives will be the most appropriate will depend entirely upon local conditions and the nature of the available power supply. The steam engine or steam turbine drive is perhaps the most common, since some steam must be present for the supply of the heating coils, and since, too, the exhaust of the engine or turbine may be used to supplement the live steam used for heating. See Art. 114. Pan housings are made in many different styles, and of various materials, the more readily to fit any given set of conditions. Materials employed may be of brick, wood, sheet steel or combinations of these. Steel housings are the most common and are made in such a variety of patterns as will fit any requirement of plenum duct direction. What are known as full housings are those where the entire fan wheel is encased with steel and the entire unit is self-con- 122 HEATING AND VENTILATION tained and above the floor line. Three-quarter housings are those where only the upper three-fourths of the fan wheel is encased, the completion of the air-sweep around the paddles being obtained by properly forming the brick foun- dation upon which the fan is installed. The larger fans are commonly three-quarter housed, especially if they are to deliver air directly into underground ducts. Fig. 58 shows a full housing and Fig. 60 a three-quarter housing. The circular opening in the housing around the shaft of the wheel is the inlet of the fan, the air being thrown by centrifugal force to the periphery and at the same time given a circular motion, thus leaving the fan tan- gentially through the discharge opening. This discharge may be had delivering at any angle around the wheel, and fans may be had with two or more discharge openings, usu- PLENUM WARM AIR HEATING 123 ally referred to as "multiple discharge fans," as shown in Fig. 61. Fig. 61. 94. Fresh Air Entrance to Building: and to Rooms: The air may enter through the building wall at the ground level or it may be taken from a stack built for the pur- pose, providing a down draft with entrance for the air at the top. This may be done in case rio washing or clean- ing systems are applied and in case the air carries a great deal of dust or dirt in from the street or from other similar places. Usually in isolated plants or in small cities, the air is taken in near the ground level from some area- way that is fairly free from dust. In the larger cities, however, either a washing system is installed to cleanse the air before it is sent around to the rooms, or the air is taken from an elevation somewhat above the ground as spoken of before. The velocity of the air should be from 700 to 1000 feet per minute at this point and where grill work or shutters of any sort are put in the opening, they are usually so planned as not to obstruct the flow of the air seriously. Usually a plain flat wire screen is placed 124 HEATING AND VENTILATION in the opening to keep out leaves, and doors are swung from the inside in such a way as to be thrown open, leaving practically the full value of the opening as a net area. Air entrance to rooms is accomplished through reg- isters or gratings which cover the ends of rectangular ducts or conduits called stacks, built into the brick walls and open- ing Into the respective rooms much as shown in section by Fig. 20. Register sizes considered standard are given in Table 14, Appendix. The velocity of the air at a plenum register may be somewhat higher than with a simple fur- nace, installation. With the plenum system the heat reg- isters are usually placed well above the heads of the occu- pants, near the ceiling, and the vent registers usually near the floor. Velocities allowable at registers and up stacks are shown in Table XIII, page 136. 95. Plenum Heating: Surfaces: Heating surfaces as used to-day in connection with plenum systems may be divided into two classes: coil surface, made of loops of 1 or 1% inch wrought iron pipe and cast surface, made of hollow rectangular castings provided with numerous staggered pro- jections to increase the outside surface and provide greater air contact. To make a neater of either kind of surface, successive units are placed side by side, until the requisite 'total area and depth has been obtained. See Arts. 110 and 111. Coil surface is of three kinds, that hav- ing the pipes inserted vertically into a hori- zontal cast iron header which forms the base of the section, Fig. 62, that having the pipes hori- zontally between two vertical side headers, Fig. 63, and that having one header vertical and one header horizontal called the mitre coil, Fig. 64. The first and last forms shown are made Fig. 62. with two, three or four PLENUM WARM AIR HEATING 125 pipes in depth. The standard number of pipes in any one section is four. Sometimes these pipes are spaced in straight lines parallel with the wind and sometimes are staggered. Staggered spacing no doubt makes each pipe slightly more ef- ficient but it adds friction to the fan. Efficiency tests of both spacings. however, show little difference in these methods. The horizontal sections and the mitre sections present this ad- vantage over the vertical pipe sections, that the steam and condensation is always flowing in the same direction and JHg. 63. =) drainage is very simple. With the vertical pipe section, steam in one half of the pipes must pass upward against the di ection of the flow of con- densation or it must carry the condensation with it. That half of the header supplying pipes which carry steam up- ward is usually drained for condensation by a small hole directly* into the return with the result that steam often blows through the header Fig. 64. 126 HEATING AND VENTILATION without traversing the pipe circuits. The third, or mitre section, in addition to per- fect drainage, has perfect ex- pansion; the vertical header serving as a steam supply, and the horizontal header as a drain, permit every pipe to assume any position nec- essary to account for a rea- sonable change of length. Cast iron radiating surface for plenum systems is shown in Fig. 65. It is composed, primarily, of sections not un- like the sections of an ordi- nary direct radiator in the way in which they are joined together at the top and bot- tom by nipples, thus forming what is termed a stack. Stacks are again assembled, one in front of another, with respect to the direction in which the air passes through them, the completed heater being then more or less cubical in pro- portion. The figure shows a ^_ Condensation' heater two sections in depth Fig. 65. and ten sections in width. Provided the conditions demand it, the heater may be built two or even three stacks in height, thus doubling or tripling the gross wind area. See Art. 111. Sections are usually made in but one thickness, 9 inches, and in three heights, 40 inches, 50 inches and 60 inches, pre- senting respectively, 11.5, 14 and 17 square feet of surface. It is unusual to assemble less than five or more than twenty- five sections to the stack. By the proper adjustment of num- ber of sections to the stack, and of stacks to the heater, any requirement of hot blast work may be met. PLENUM WARM AIR HEATING 127 ELEVATION. Fig. 66. Fan Room Layout with Single Ducts along Basement Ceiling and all Mixing Dampers at Plenum Chamber. 12S HEATING AND VENTILATION Pig. 67. E an Room Layout with Double Underground Ducts and Mixing Dampers at Base of Room Stacks. PLENUM WARM AIR HEATING 129 No matter what kind or type of heater may be selected, certain methods of installing- them have become common. They may be placed on either the suction or the force side of the fan, usually the former in drying- or evaporating- plants, but more often the latter in heating- plants. Because of their weight, ample and firm foundations must be pro- vided. In most installations for heating- purposes, where both tempered and heated air is supplied, the heater should be raised on its foundation 18 to 24 inches to allow a damper and passage way for tempered air. 96. Division of Coil Surface: It is considered best practice to install a hot blast heater in two parts, known as the tempering coil and the heating coil. In the calculations. Arts. 107-111, the total heating surf ace- $s first obtained and then this is split up into whatever arrangement is desired. The tempering coils should be placed in the air passageway, just within the intake for the building, and should contain from one-fourth to one-third of the total heating- surface. In this way the air is tempered before it reaches any other apparatus, thus protecting from accumulation of frost on fan and bearings and aiding in the process of lubrication. The .main heat coil is placed just beyond the fan on its force side. Exhaust steam from the engine is most commonly used in the tempering coil only, and live steam of properly reduced pressure in the main heater. This may be varied by conditions, however, and all surface supplied by exhaust steam if it is thought advisable. 97. Single Duct Plenum System: Duct systems in hot blast work may be either of the single duct type or the double duct type. In the single duct plant, every horizontal duct is carried independently from the base of the room to be heated to the small room called the plenum chamber, which receives the hot blast from the heater. This chamber is divided into an upper and a lower part, the upper receiving the heated air that has been forced through the heater, while the lower part receives only air that has been through the tempering coils. The leader duct, from the base of each vertical room-duct, is led directly opposite the parti- tion between these two chambers, and a damper, regulated by some system of automatic control from the rooms to be heated, governs whether cool air from the lower chamber, or hot air from the upper chamber, or a mixture of both, 130 HEATING AND VENTILATION shall be sent to the rooms. It can be readily seen that this system produces rather a complicated net work of dampers and ducts at the plenum chamber and this disadvantage has limited its use very much. 98. Double Duct Plenum Systems: As its name indi- cates, this system runs a double leader duct from the plenum chamber to the base of each vertical room-duct, the upper one of these ducts being in direct communication with the upper part of the .plenum chamber and carries hot air, while the lower one is in communication with the lower part of the plenum chamber and carries cool air. No mix- ing- or throttling is done except at the base of the vertical room-duct, where the mixing damper is lo- cated, it being controlled by hand or by automatics directly from the room above. With this scheme it is evident that the leader ducts for each room need not be run singly, but all the ducts having the same general direction combined in one large double trunk, from which branches are taken to the various room-ducts as required. Fig. 68. The difference between the two systems is shown by the two sketches, Figs. 66 and 67. A hot blast plant may be installed as a basement or as a sub-basement system. If the former, the leaders will be suspended from the basement ceiling and constructed, usu- ally, of sheet metal, thus forming what is often called a "false ceiling." If the latter, they will be just below the floor of the basement and will be constructed of brick and mortar, or of concrete, about four inches thick. For designs PLENUM WARM AIR HEATING 131 of conduits, ducts and dampers, see Figs. 60, 66, 67 and 68, the last showing a simple and direct installation often applied to factories of several stories. Fig. 69 shows a complete steel housed plenum unit of fan, coils, dampers, and duct connections. Fig. 69. 99. Air Washing and Humidifying Systems: In con- nection with mechanical warm air heating and ventilating systems, there is often installed apparatus for washing and humidifying the air. In crowded city districts where the air is laden with dust, soot, th.e products of combus- tion and other harmful gases, its purification and moisten- ing becomes a most important problem. The plenum system of heating and ventilating lends itself most readily to the solution of this problem, with the result that modern practice is tending more each day toward the combined installation of ventilating and humidifying apparatus. Fig. 70 shows a plenum system augmented by an air washing, purifying and humidifying apparatus. A purifier usually contemplates the installation of two parts, a washer and an eliminator. The washer consists essen- tially of an air duct, usually located immediately behind the tempering coils, and provided with streams or sprays of water through which the air must pass. Numerous schemes for breaking up the water in the finest sprays are on the market, and their relative merits may be judged from trade literature. Having caught the dust particles and dissolved the soluble gases from the air, the water falls to a collecting pan at the bottom of the spray chamber, and from there is again pumped through the spraying nozzles. As the water becomes too dirty or too warm, a fresh supply is 132 HEATING AND VENTILATION delivered to the collecting- pan. A small independent cen- trifugal pump is commonly used for the circulation of the spray water. Fig. 70. After passing through the washer, the air next encoun- ters the eliminator, the purpose of which is to remove or eliminate the surplus moisture and water particles remain- ing suspended in the air. This is accomplished by an arrangement of more or less complicated baffle plates, which cause the air to change its direction suddenly many times in succession, with the effect that the water particles im- pinge upon and adhere to, the baffle plates. These are suit- ably drained to the collecting- pan beneath the washer. As the air leaves the eliminator and enters the fan it may be relieved, with good apparatus, of 98 per cent, of all dust and dirt, may be supplied with moisture to very near the saturation point, and, in summer time under favorable con- ditions, may be cooled from 5 to 10 degrees lower than the atmosphere. This is due to the cooling effect of vaporizing part of the water. Special air cooling plants have been installed in connec- tion with the plenum system of ventilation, whereby refrig- erated brine could be circulated in the regular heating coils. The description of such a plant with data, may be found in the transactions of the A. S. H. & V. E. for the year 1908. CHAPTER X. MECHANICAL, WARM AIR HEATING AND VENTILATING SYSTEM. AIR, HEATING SURFACE AND STEAM REQUIREMENT. PRINCIPLES OF THE DESIGN. 100. Definitions of Terms: In the work under this gen- eral heading, some of the technical abbreviations that are frequently used are the following: H = B. t. u. heat loss per hour by the formula, Hv = B. t. u. heat loss per hour by ventilation, H' = total B. t. u. loss including ventilation loss, Q = cubic feet of air used per hour as a heat carrier, Q f = cubic feet of air used including extra air for ventila- tion, R = total square feet of heating surface in indirect heaters, ts = temperature of the steam or water in the heaters, t = highest temperature of the air at the register (let this be the same as the temperature of the air upon leaving the heater), t' = temperature of the air in the room, tv = temperature of the air at the register when extra air is used for ventilation, to = temperature of the outside air, K = rate of transmission of heat per square foot of surface per degree difference per hour, N = the number of persons to be provided with ventilation, V = velocity in feet per minute and v = velocity in feet per second. Other abbre- viations are explained in the text. 101. Theoretical Considerations: For illustrative pur- poses, references will frequently be made throughout this discussion to a sample plenum design, Figs. 74, 75 and 76. These show the essential points of most plenum work and will serve as a basis for the applications. In working up any complete design the following points should be theo- retically considered for each room: the heat loss, the cubic feet of air per hour needed as a heat carrier (this should be checked for ventilation), .the net area of the register in square inches, the catalog size of the register, and the area and size of the ducts. In addition to these the follow- ing should be investigated for the entire plant: the size of the main leader at the plenum chamber, the size of the principal leader branches, the square feet of heating sur- face in the coils, the lineal feet of coils, the arrangements of the coils in groups and sections, the horse power and 134 HEATING AND VENTILATION the revolutions per minute of the fan including the sizes of the inlet and the outlet of the fan, the horse power of the engine including the diameter and the length of stroke, and the pounds of steam condensed per hour in the coils. Fresh air is taken into the building at the assumed lowest temperature, to degrees, is carried over heated coils and raised to t degrees, is propelled by fans through ducts to the rooms and then exhausted through vent ducts to the outside air, thus completing the cycle. It will be the object to so discuss this cycle that it will be general and so it will apply to any case which may be brought up. 102. Heat Loss and Cubic Feet of Air Exhausted per Hour: It is assumed here, that in all mechanical draft heating and ventilating systems, tlie circulating air is all taken from tlie outside and thrown away after being used. Some installa- tions have arrangements for returning the room air to the coils, for reheating, but such schemes should be considered as features added to the regular design rather than as being a necessary part of it. It is best to design the plant with the understanding that all the air is to be thrown away, then it will be large enough for any service that it is expected to handle. Having found H by some acceptable formula, the total heat loss is (compare with Arts. 29 and 36.) (Q or Q') (f to) H' = H -\ (40) 55 When *' = 70 and to = zero, this formula reduces to H' = H + 1.27 (Q or Q') To determine whether Qo or Q f will be used find how many people would be provided with ventilating air with the volume Q. If Q = 55 H -j- (t *'), * = 140 and f = 70, then 55 H H H N = = = approximately (41) 1800 (t O 2290 2300 If more people than N will be using the room at any one time, then Q' will be used instead and this value would be 1800 times the number of persons in the room. In any ordinary case, Q will be sufficient. When this is so, formula (40) reduces to H' = 2 H (42) PLENUM WARM AIR HEATING 135 The reasoning- of this formula is easily seen when it is re- membered that the heat given off from the air in dropping from the register temperature, 140, to the room tempera- ture, 70% goes to the radiation and leakage losses, H, while that given off from the inside temperature, 70, to that of the outside temperature, 0, is charged up to ventilation losses, Hv. Since, then, these values are equal, H' = H -j- H = 2 H. APPLICATION. Referring to Fig. 75, room 15, and Table XXVI, page 140, it is seen that the calculated heat loss H, for this room, with f = 70 and to = 0, is 70224 B. t. u. per hour; also, that the cubic feet of air, Q, if t = 140, is 54775 per hour. Applying formula (42), the total heat loss, H', be- comes 140448 B. t. u. per hour, or twice the amount found by the heat loss formula. With 54775 cubic feet of air sent to the room per hour, this will provide good ventilation for thirty persons. Suppose, however, that fifty persons were to be provided for; this would require 50 X 1800 90000 cubic feet of air per hour. With this increased number of people in the room, the total heat loss would not be as stated above, but would be according to formula (40) 90000- (70 0) B' = 70224 H 184864. 55 103. Temperature of the Entering Air at the Register: In plenum work, the registers are placed higher in the wall and the velocity of the air is usually carried a little higher than in furnace work. It may be said that 140 is probably the accepted temperature for design, excepting where an extra amount of air is demanded for ventilation purposes. In the latter case, the temperature of the air would necessarily drop below 140 in order that the room would not be overheated. The general formula is 55 H tv = t' + (43) APPLICATION. Referring to room 15 and (compare with Art. 38) assuming the heat loss to have been figured as before with ventilating air supplied sufficient for 50 per- sons, 90000 cubic feet per hour, then the temperature of the air at the register is 55 H t = 70 H = 103%* 90000 136 HEATING AND VENTILATION The temperature of the air at the register is the same or slightly less than the temperature of the air upon leaving the coils. If this room were to be the only one heated, then the coils would be figured for a final temper- ature of the air at 104, but other rooms may have air entering at higher temperatures, hence the temperature t upon leaving the coils should be that of the highest t at the registers. 104. Cubic Feet of Air needed per Hour: The following amount of air will be needed per hour as a heat carrier (compare with Art. 36). 55 H H Q = ; where t = 140 and V 70, Q * t' 1.27 If extra air be needed for ventilation, Q' = 1800 N. 105. Air Velocities, V, in the Plenum System: Table XIII gives the velocities in feet per minute that have been found to give good satisfaction in connection with blower systems. TABLE XIII. Air Velocities in the Plenum System. Fresh Aii- Intake Over Coils Main Duct Near Fan Smaller Branch Ducts Stacks Registrs or other Open'gs Offices, Schools, etc. s ? S> 800 to 1200 F. P. M. Average KXK) F. P. M. 1200 to 1800 say 1500 800 to 1200 say 900 500 to 700 say 600 300 to 400 say 300 Auditoriums, Ohurches.etc. 1500 to 2000 say 1800 1000 to 1500 say 1200 600 to 800 say 700 400 to 600 say 400 Shops and Factories. 1500 to 3000 say 2000 1000 to 2000 say 1500 600 to 1000 say 800 400 to 800 say 500 106. Cross Sectional Area of Registers, Ducts, etc: With the above velocities in feet per minute, the square inches of net opening at any part of the circulating sys- tem can be obtained by direct substitution in the general formula. 144 (0 or Q') A = (Q or Q') X = 2.4 (44) 60 V V PLENUM WARM AIR HEATING 137 The calculated duct sizes, of course, refer to the warm air duct. The cold air duct in double duct systems need not be so large because on warm days, when only tempered air is needed, the steam may be turned off from one or more of the heaters and the warm air duct can then be used to furnish what otherwise would be required from the cold air duct. On account of this flexibility, it seems only nec- essary to make the cold air duct about one-half the cross sectional area of the warm air duct. For convenience of installation, therefore, it would be well to make the form- er of equal width to the latter and one-half as deep, unless by so doing the cold air duct becomes too shallow. APPLICATION. Assuming 2000000 cubic feet of air to pass through the main heat duct, 5 ig. 74, per hour at the velocity of 1800 feet per minute, the duct will be approximately 20 square feet in cross section, or 2y 2 by 8 feet. The two main branches at B, will carry about 800000 cubic feet per hour each at the same velocity and will be 7.4 square feet in area or, say, 2 by 4 feet. The same branches at C, will carry about 400000 cubic feet per hour each at a velocity of 1500 feet per minute and will be 4.4 square feet in area or, say, 2 by 2% feet and the branch D, will carry about 300000 cubic feet at a velocity of 1200 feet per minute and will be, say, 1^2 by 2% feet. The stack sizes were first figured for the velocity of 600 feet per minute. These sizes were then made to fit the lay- ing of the brick work such that the velocities would be anywhere between 300 to 600 feet per minute. The net register was figured for an air velocity of 300 feet per minute and the gross registers were assumed to be 1.6 times the net area. See Art. 126. 107. Square Feet of Heating: Surface, R, in the Coils: To determine theoretically the number of square feet of heating surface in the coils of an indirect heater, the fol- lowing formula may be used, H' R = (45) E ( t ...l^l \ 2 Since the coils are figured from the entire building loss, H r will include the sum of all the heat losses of the various rooms. The chief concern in the use of this formula, as 138 HEATING AND VENTILATION stated, is to determine the best value for K, the rate of transmission. Prof. Carpenter in H. and V. B., Art. 52, quotes extensively from experiments with coils in blower systems of heating and summarizes all in the formula, K = 2 + 1.3 V^T where v = average velocity of air over the coils in feet per second. With the four velocities most appli- cable to this part of the work, i. e., 800, 1000, 1200 and 1500 feet per minute, this becomes 800 feet per minute K = 6.9 1000 feet per minute K 7.3 1200 feet per minute K 7.8 1500 feet per minute K 8.5 In the table of probable efficiencies of indirect radiators in Art. 54 by the same author, the values are somewhat high- er, being, 750 feet per minute K = 7.1 1050 feet per minute K = 8.35 1200 feet per minute K = 9. 1500 feet per minute K = 10. The values of K, as given here, are certainly very safe when compared to quotations from other experimenters, some of them exceeding these values by 50 per cent. It is always well to remember that a coil that has been in service for some time is less efficient than a new coil, be- cause of the dirt and oil deposits upon the surface, hence it is best in designing, not to take extreme values for ef- ficiency. Assuming K = 8.5 and 1000 feet per minute air velocity, which are probably the best values to use in the calculations, also t = 227 (5 pounds gage pressure), t 140 and to = 0, formula 45 becomes E r H' H' R = say (46) / 140 + 0\ 1335 1400 8.5/227 } Table XIV quoted by Mr. C. L. Hubbard in Power Heat- ing & Ventilation, Part III, page 557, gives the efficiencies of forced blast pipe heaters and the temperatures of air delivered. PLENUM WARM AIR HEATING 139 TABLE XIV. Efficiencies of Forced-Blast Pipe Heaters, and Temperatures of Air Delivered. Velocity of air over coils at 800 feet per minute. Rows of Pipe Deep Tetnp. to which the air will be raised from zero Efficiency of the heating sur- face in B.t.u.per sq.ft. perhr Steam pressure in heater Steam pressure in heater 5 Ib. 20 Ib. 60 Ib. 5 Ib. 20 Ib. 60 Ib. 4 30 35 45 1600 1800 2000 6 50 55 65 1600 1800 2000 8 65 70 85 1500 1650 1850 10 80 90 105 1500 1650 1850 12 95 105 125 1500 1650 1850 14 105 120 140 1400 1500 1700 16 120 130 150 1400 1500 1700 18 130 140 160 1300 1400 1600 20 140 150 170 1300 1400 1600 For a velocity of 1000 feet per minute multiply the temperatures given in the table by 0.9 and the efficiencies by 1.1. Mr. F. R. Still of the American Blower Co., Detroit, gives the following formula for the total B. t. u. trans- mitted per square foot of surface per hour between the temperature of the steam and that of the entering air. Total B. t. u. transmitted = c ^v^ts fo) (47) in which case v is the velocity in feet per second and c is a constant as follows: 140 HEATING AND VENTILATION TABLE XV. Values of c. Safe Factor Max. Factor 1 section 4 rows of pipe 8.45 4.4 2 sections 8 rows of pipe 3. 8-4 3 sections 12 rows of pipe 2-63 2.85 4 sections 16 rows of pipe 2.88 2.45 5 sections 20 rows of pipe 2.12 2.2 6 sections 24 rows of pipe 1.95 2.05 7 sections 28 rows of pipe 1.80 1.95 8 sections 82 rows of pipe 1.65 1.85 9 sections 86 rows of pipe 1.52 1.8 10 sections 40 rows of pipe 1-4 1.75 From the above values of c, Table XVI has been com- piled, assuming * s = 227, to and c = a safe value. TABLE XVI. 31 Total transmission in B. t. u. per sq. ft. per hour. * = 227; * = s 4 8 12 16 20 24 28 82 800 2840 2470 2164 1920 1750 1606 1450 1860 1000 8200 2790 2440 2170 1900 1810 1670 1535 1200 8500 8040 2670 2860 2150 1980 1825 1678 1500 8950 8400 2981 2645 2400 2220 2020 1870 Cast iron heaters are being used for indirect heating in many cases, replacing the old-fashioned pipe coil heaters. The efficiency of these heaters is, according to tests, about the same as that of the pipe coil heaters and hence formulas 45 and 46 would apply in the same way for both kinds. PLENUM WARM AIR HEATING 141 Table XVII gives values of heat transmission for various sections, taken from tests upon Vento cast iron heaters set up in banks, and is added as a means of comparison with the values quoted on the pipe coil heaters. TABLE XVII. Rate of Transmission of Heat, K, through Vento Coils. Steam 227, air entering at 0. Velocities of air over coils. Sections 800 1000 1200 1500 1 7.6 8.8 10. 11.8 2 7.1 8.2 9.2 10.5 3 6.6 7.7 8.6 9.7 4 6".l 7.1 7.9 9. 5 5.6 6.5 7-8 8-8 6 5.2 6. 6.7 7-7 7 4.8 5.5 6-2 7-1 In applying these values of K to formula 45 it should be remembered that to would be used instead of K - APPLICATION 1. Where Heating Only is Considered. Refer ring- to Table XXV let H for the entire building be 1483251. Then from Art. 104, Q = 1156935, by formula 42, H f = 2966502 and by formula 46, the coil surface is 2966502 = 2222 square feet. R = 8.5 ^227 - 140 + \ With three lineal feet of 1 inch pipe per square foot of surface, we have 6666 lineal feet of coils in the heater. APPLICATION 2. Where Ventilation is Considered. Assume 1100 people in the building on a zero day and Q' = 2000000, then, H' = 1483251 + 1.27 X 2000000 = 4023251 and 4023251 R = =3014 sq. feet = 9042 lineal feet. 8.5^227 - 142 HEATING AND VENTILATION This value is probably the greatest amount that would be needed. In such a case, when the rooms were supplied with extra air, the register temperatures over the entire building- may be less than 140 degrees. Suppose in this case the temperature to be, by formula 43, t = 70 4- 55 X 1483251 -f- 2000000 = 111, then 4023251 B = = 2760 sq. ft. = 8280 lineal ft. Ill + / '('"- In using- this formula, the value t = 140 is to be recom- mended wherever part of the rooms are not provided with extra amounts of ventilating air. By so doing the ducts and registers may be held down to a more moderate size and at the same time give a safer figure for the heating surface. 108. Approximate Rules for Plenum Heating Surfaces: The following approximate rules are sometimes used in checking up heating surface in the coils. These are not recommended and should be used with caution. Rule 1. "Allow one lineal foot of 1 inch pipe for each 65 to 125 cubic feet of room space"; 65 for office buildings, schools, etc. and 125 for shops and laboratories. Since this building has approximately 500000 cubic feet of room space, it gives 7700 lineal feet of 1 inch pipe in the heater. Rule 2. "Allow 200 lineal feet of 1 inch pipe for each 1000 cubic feet of air per minute at a velocity of 1500 feet per minute." Applying to the above building when the air moves over the coils at 1000 feet per minute, the heated surface is only about four-fifths as valuable and would require 250 lineal feet per each 1000 cubic feet of air per minute. This gives 8333 lineal feet of coils. 109. Final Air Temperatures: Since the amount of heat transmitted is directly proportional to the difference of temperature between the two sides of the metal, it is readily seen that the first coils in the bank are the most efficient, and that this efficiency drops oft' rapidly as the air becomes heated in passing over the coils. Final tem- peratures, for different numbers of coil sections in banks, have been found by experiment and may be taken from Table XVIII. See also Table XIV, page 139. PLENUM WARM AIR HEATING 143 TABLE XVIII. Temperatures of air upon leaving Coils, steam 227, air entering- at 0. Sections No. of Bows Velocities of air through coils in F. P. M. 800 1000 1200 1500 1 4 42 33 28 23 2 8 71 62 56 52 3 12 96 87 80 75 4 16 119 108 101 93 5 20 136 125 116 108 6 24 153 140 131 120 7 28 169 155 143 131 8 32 183 166 154 141 These temperatures may be increased about 10 per cent, for 20 pounds gage pressure. Table XIX shows similar results quoted for the Vento cast iron heaters. TABLE XIX. Temperatures of air upon leaving Vento Coils, steam 227, air entering at 0. Number Velocities of air through coils in F. P. M. 01 STACKS deep 800 1000 1200 1500 1 38 34 31 29 2 69 62 59 55 3 98 89 83 76 4 120 110 103 94 5 135 125 118 109 6 148 138 130 120 7 155 145 138 128 144 HEATING AND VENTILATION 110. Arrangement of Coils in Pipe Heaters: Coil sec- tions are arranged with 2, 3 and 4 rows of pipes per sec- tion. Unless special reference is made to this point, the latter value is understood. Having found the total square feet of heating surface in the heater, obtain from the tem- perature tables the number of sections deep the heater will need to be to produce the desired temperature, and find the number of square feet of heating surface per section and per row of coils. Let this latter value be A. Also find the net wind area across the coils, assuming, say, 1000 feet per minute velocity. From the net wind area, find the gross cross sectional area of the heater by the value. Gross wind area = 2.5 times net wind area. (48) From the gross area the size of the heater may be selected. In selecting the heater, the following check should be ap- plied. Find the number of square feet of heating surface, B, in each row of the coils as figured from the gross area and compare with A. These must be made to agree. Let the net area between the tubes, N. A., the space occupied by the tubes, T. A., and the gross cross sectional wind area through the tube, Q. W. A., be respectively Q or Q' Q or Q' Q or Q' N. A. = ; T. A. = ; and G. W. A. = . (49) 60 V 40 V 24 7 Since the cross sectional space T. A. occupied by the tubes is to the coil surface per row as 1 : 3.1416, the total coil surface in one row of tubes is 3.1416 (Q or Q') (Q or Q') B! = = .08 40 7 7 Reduced to the basis of the net area, N. A., we have Ri = 4.8 times N. A. (50) If B is greater than A, then the total heating surface must be increased in that proportion, since the Dumber of sections cannot be less or the final temperature will drop below the required degree, and the net cross section cannot be less or the velocity of the air will be greater than that desired. On the other hand, suppose B should be less than A. In that case the total heating surface will not change from that calculated. Either B may remain the same as calculated and the number of sections increased (if de- sirable) until all the heating surface is accounted for, or A may remain constant and B may be increased. The latter PLENUM WARM AIR HEATING 145 method is probably a better one since it gives larger wind areas and consequently reduced velocities of the air, which in many cases is desirable, and avoids placing heating sur- face at the rear of the bank where it is less efficient. Assembled sections of pipe coil heaters are supplied by manufacturers from the smallest size of 3 feet x 3 feet, to the largest size of 10 feet x 10 feet; these dimensions being those of the gross cross-sectional area, and noi dimension*? over all. Between the two limits, both height and breadth usually vary by 6 inch increments. For exact sizes, consult dimension tables in manufacturers' catalogs. APPLICATION 1. In Article 107, let R = 2222, Q = 1156935, V = 1000 and t = 140; then from Table XVIII the heater will require 24 rows of coils in depth to give the required tem- perature. Next find RI = 93 square feet of heating surface per row, also N. A. = 19.7; T. A. = 29.1; and Q. W. A. = 48.5. Checking N. A. with an air velocity of 1000 feet per min- ute gives 1156935 -=- (60 X 1000) =19.3 square feet, which shows that the above arrangement is satisfactory. Now from the value G. W. A. = 48.5 select a heater, say, 6 feet x 8 feet. APPLICATION 2. In article 107, let R = 3014, Q' = 2000000, 7 = 1000 and t = 140; then as before, the heater will need 24 rows of coils. Find in this case RI = 126 and N. A. 26.3; T. A. = 39.4; and Q. W. A. = 65.7. Checking from the volume of air delivered, obtain N. A. = 33.3; T. A. = 50; and G. W. A. = 83.3. From N. A. = 33.3 find B x = 160, which shows that it will be necessary to increase the total heating surface to, j-^ LZ6 X 3014 = 3826 square feet. If it were considered advisable to have 1200 feet air velocity the heating surface per row would be reduced to 135 and the temperature, t, would be reduced to 131. Both conditions are reasonable and in many cases would be considered satisfactory. Selecting the heater for the gross area of 83.3 square feet, from the catalog size, would probably give a single section 9 feet x 9 feet or a double section, each part 6 feet x 7 feet. 111. Arrangement of Sections and Stacks in Vento Cast Iron Heaters: Applying only to Case 2, Art. 107, let R = 1*6 HEATING AND VENTILATION 3014, Q' = 2000000, V = 1000 N. A. (least value) = 33.3, and * = 140; also take for cast iron heaters G. W. A. = 2.3 times N. A. (51) From Table 34, Appendix, either of the following arrange- ments will give the necessary N. A. First. Six stacks, each 620 square feet, and built up of 20 sections 50 inches high on top of 20 sections, 60 inches high, making a total of 110 inches high and 100 inches long. Second. Seven stacks each 612 square feet, and built up of 18 sections^ 60 inches high on top of 18 sections 60 inches high, making a total of 120 inches high and 90 inches long. With the above ar- rangement of, say, six stacks, Table XIX gives a possible temperature of 138 degrees, which is slightly below what is required. It also gives a total heating surface of approxi- mately 25 per cent, in excess of the requirement. With this arrangement it will be necessary to increase the heating surface arbitrarily or to increase the air velocity. 112. Use of Hot Water in Indirect Coils: In most cases low pressure steam is used as a heating medium in the indirect coils. It is possible, however, to rse hot water instead, where a good supply is to be had. In such an arrangement the coils will be figured from formula (45), using all values the same as for steam excepting t s , which would be replaced by the average temperature of the water. The piping connections and the arrangements of the coils would follow the same general suggestions as already stated. 113. Pounds of Steam Condensed per Square Foot of Heating: Surface per Hour: From Art. 107 it is readily seen that the number of pounds of condensation per hour per square foot of surface in the coils is TJt m ~ R X Heat given off per pound of condensation. APPLICATION. Let R = 3014 and W = 4023251; also let one pound of dry steam at five pounds gage in condensing to water at 212 degrees give off 1155.6 180.9 = 974.7, say, 975 B. t. u. (see Tables 2 and 6, Appendix.), then 4023251 m = = 1.37 pounds. 3014 X 975 This amount should, of course, be considered an average. The first and last section in any bank would vary above PLENUM WARM AIR HEATING 147 and below this amount by as much as 50 per cent, in the average plant. The first coils should condense as much as 2 pounds of steam per square foot of surface per hour. 114. Pounds of Dry Steam Needed in Excess of the Exhaust Steam Given off Prom the Engine: Let the heat- ing value of the exhaust steam from the engine be, say, 85 per cent, of that of good dry steam, also let the engine use 40 pounds of dry steam per horse power hour in driv- ing the fan. From Art. 124, the engine will use 40 X 13.6 = 544 pounds of steam per hour and the heating value will be, 975 X .85 = 828 B. t. u. per pound or 828 X 544 = 450432 B. t. u. total per hour. Then 4023251 450432 = 3572819 B. t. u., and 3572819 975 3664 pounds of steam. The boiler will then supply to the engine and coils, 3664 + 544 = 4208 pounds of steam total and will represent, approximately, 4208 -r- 30 = 140 boiler horse power. CHAPTER XL MECHANICAL, WARM AIR HEATING AND VENTILATING SYSTEM. PRINCIPLES OF THE DESIGN, CONTINUED. FANS AND FAN DRIVES. 115. Theoretical Air Velocity: The theoretical velocity of air v, flowing from any pressure, pa, to any pressure, pb, is obtained from the general equation v = ^2gh, where v is given in feet per second, g 32.16 and Ji head in feet producing flow. This latter value may be easily changed from feet of head to pounds pressure and vice-versa. When exhausting air from any enclosed space into another space containing air at a different density, the force which causes movement of the air is pa p& say, PX. These recorded pressures may be taken by any stand- ard type of pressure gage and show pressures above the atmosphere. When exhausting into the atmosphere, the value pb is zero and pa = p x . The fact that a difference of pressure exists between two points indicates that there are either two actual columns (or equivalent as in Fig. 8) of air of different densities connected and producing motion, or that, by mechanical means, a pressure difference is crea- ted which may easily be reduced to an equivalent head h, in feet, by dividing the pressure head by the density of the air, as pressure difference pa pi> density d Let pa p& = PX = ounces of pressure per square inch of area producing velocity of the air; also, let g = acceleration due to gravity = 32.16 and d = density, or weight, of one cubic foot of dry air at 60 degrees and at atmospheric pres- sure (Table 9, Appendix, then, substituting in the gen- eral equation, we have 64.32 X 144p* = 87 VP* (53) .0764 X 16 Since the pressure producing flow is usually measured in inches of water, tiw, the above can be changed to equiva- lent height of air column by weight of water, per cu. ft. at given temp. X , weight of air at given temperature X 12 (54) PLENUM WARM AIR HEATING 149 Applying this to dry air at 60 degrees and water at the same temperature (Tables 9 and 6, also Art. 15), 62.37 Tiw h 68 h w 12 X .0764 then substituting in the general equation, find v = V 64 -32 X 68 h w = 66.2 Vtiw (55) Formula 54 at the temperatures 50, 55, 60, 65 and 70 degrees respectively, gives results varying between v = 65.5 V^ for 50 degrees and v 66.5 \T~^ for 70 degrees, which leads to the approximate general rule that the theoretical velocity of air, when measured by a water column gage that measures in inches of water, equals sixty-six times the square root of the height of the column in inches. Stated as a formula v = 66 ^/^i^^ (56) For calculations requiring accuracy, several factors would affect the final result; these are, atmospheric pres- sure, humidity, density of the air and temperature of the air. Let the atmospheric pressure and the humidity be constant, since these would affect the result but little, and take into account, first, the density of the air. Let the pressure of the atmosphere be 29.92 inches of mercury (14.7 pounds = 235 ounces per square inch area) then, since the density is proportional to the absolute pressure, the temperature remaining constant, we have from form- ula 53 64.32 X 144 px I px = 1336 \ (57) 235 + p x 235 + .0764 X 16 X 235 Also, from the relation existing between (53) and (55), formula 57 reduces to / h* v = 1336 \ (58) " 407 + h w From formulas 57 and 58 the second columns in Tables XX and XXI have been calculated. APPLICATION. Air is exhausted from an orifice in an air duct into the atmosphere. The pressure of the air within the duct is one ounce by pressure gage or 1.74 inches by a Pitot tube. Assuming the air to be dry and the barometer standing at 29.92 inches when the water in the tube is 60 degrees, what is the velocity of the air? By the approxi- mate formulas (53) and (56) 150 HEATING AND VENTILATION v = 87 V3~= 87 F. P. 8. and v = 66 yi^'4 = 87.2 F. P. 8. By formulas (57) and (58) 1 v = 1336 A/ = 86.3 F. P. 8. * 235+1 / OT~ and v = 1336 A/ = 87.1 F. P. 8. * 407 + 1.74 * TABLE XX. Column 2 figured from formula 57. Pressure In ounces per sq. Inch. Velocity of dry air at 6QO es- caping: into the atmosphere through any shaped orifice in any pipe or reservoir in which a griven pressure is main- tained. Vol. of air in cu ft. which may be discharged in 1 min. through an orifice having an effective area of discharge o f 1 sq. inch. Ool. 3 -4- 144 H. P. required to move the given vol. of air under the given con- ditions o f dis- charge. ( Col. 3 X Col. 1 ) Ft. per sec. Ft. per min. 16X33000 5* 30.80 1848-00 12.83 0.00044 % 43.56 2613.60 18.15 000124 % 68.27 8196.20 22.19 0.00227 % 61-56 3693-60 25-65 0.00349 ft 68.79 4127.40 28 66 0.00489 3 /4 75-35 4521.00 31.47 0.00642 % 81.87 4882.20 83.90 0.00809 1 86.97 5218-20 36-24 0-00988 1H ' 92.18 5530.80 88.41 0.01178 IX 97.18 5830.80 40.49 0.01380 itt 101.90 6114.00 42.46 0.01592 1 1 A 106.40 6384.00 44-83 0.01814 itt 110.82 6649.20 46.11 0.02046 l 3 /4 114-86 6891.60 47.86 0.02284 1% 118.85 7131.00 49 V -52 9.02533 2 122.47 7348.20 51.03 0.02787 PLENUM WARM AIR HEATING 151 TABLE XXI. Column 2 figured from formula 58. Pressure in inches o f Velocity of dry air at 60 escaping into the atmosphere through any shaped orifice in any pipe or reservoir in which a given pressure is maintained. water per sq. in. Peet per second Feet per minute .1 29-04 3^56.40 .2 29.67 1780 20 .3 36.25 2175-60 .4 41.86 2511.60 .5 46.80 2708 00 .6 51.26 3075.60 .7 55 36 21.60 .8 59-10 3516-00 .9 62.60 3756.00 1. 66.14 3968.40 1.1 69-36 4161-60 1.2 72.44 4346.40 13 75-39 4523.40 1.4 78-21 4692.60 1.5 80.96 4857-60 1 6 83.59 5015.40 1.7 86-16 5169.60 1.8 88-65 5819.00 1.9 91-27 5476.20 2. 93.42 5605-20 2.1 95-72 5743-20 2 2 97 96 5877 60 2 3 100.15 6009-00 2.4 102.29 6137.40 25 104.39 6263.40 2 6 106.43 6885-80 2.7 108-46 6507 60 2.8 110.43 6 Vwt. at any T T of air = umn 4 squared t* Wt. at 4600 + eoo 1 +- Col. 3. 30 97 1.07 .93 .87 40 98 1.04 .96 .92 50 .99 1.02 .98 .96 60 1.00 1.00 .00 1.00 70 1.01 .98 .02 1.04 80 1.02 .96 .04 1.08 90 1.03 94 -06 1.13 100 1.04 .92 .09 1.19 125 1.06 .89 .12 1.25 150 1 08 .85 .18 1.39 175 1.10 .82 .22 1.49 200 1 13 79 .27 1.61 250 1.17 .78 S7 1.88 800 1.21 .68 .47 2.16 350 1.25 .64 .56 2.43 400 1.28 .60 .67 2.79 500 1.36 .54 .85 3.42 600 1.43 .49 2.04 4.16 700 1.49 .45 2.22 4.93 800 1.56 .41 2.44 5.95 116. Actual Amount of Air Exhausted: When air of any pressure is exhausted from one receptacle to another through an orifice, the actual velocity remains about the same as the theoretical velocity, being slightly reduced by friction, but the volume of air discharged is greatly reduced because PLENUM WARM AIR HEATING 153 of the contraction of the stream just as it leaves the ori- fice. The greatest contraction or least size of the jet is located from the orifice a distance of about one-half the diam- eter of the opening. A round opening is the most efficient. Since the velocity is slightly reduced and the effective area of the opening reduced a still greater amount, the actual amount of air exhausted in any given time would be found by multiplying the theoretical amount by a constant which is the product of the coefficient of reduced velocity and the coefficient of reduced area. From tests the following ap- proximate values are quoted by the Sturtevant Company in Mechanical Draft, page 152. Orifice in a thin plate, .56 Short cylindrical pipe, .75 Rounded off conical mouth piece, .98 Conical pipe, angle of convergence about 6, .92 117. Results of Tests to Determine the Relation be- tween Pressure and Velocity: In Power, Heating and Ven- tilation, page 536, Mr. Hubbard gives curves, Fig. 71, show- ing the ratio of the air-velocity pressure to the peripheral- velocity pressure in fan experiments; also, between the air- velocity pressure and the dynamic pressure for degrees of discharge opening varying from 40 per cent, to 100 per cent, or full opening. 100 10 20 30 50 60 70 80 90 100 RATIO OF EFFECT. Fig. 71. 154 HEATING AND VENTILATION In the tests a pipe, the size of the fan outlet and about 12 feet in length, was attached directly to the casing and provided with a gate at the outer end to allow for any de- gree of opening. The fan was run at constant speed and the dynamic and static pressures were measured about mid- way of the pipe at full opening. Then the opening was changed by 10 per cent, reductions and readings taken. The pressure, corresponding to the peripheral-velocity pressure, was found by formula 56 and the results of the test were plotted in curves showing ratios to this peripheral-velocity pressure. As an illustration, the relation between the air velocity pressure to the peripheral-velocity pressure for full opening and discharging into free air is .43. Since the velocities always vary as the square root of the pres- sure (v \J2gh), we find that the velocities in this case vary as V * 43 - 65 - This shows that for this one condition, the air velocity at the free opening = .65 times the peripheral velocity of the fan. For methods of measuring velocity and pressure, see Art. 15. 118. Work Performed and Horse Power Consumed in Moving Air: The foot pounds of work performed in moving air equals the product of the moving force into the distance moved through in any given time. Let pa pi> = PX = moving force of the air in ounces per square inch and A = cross-sectional area of current in square inches, then the pounds per square inch will be p x -f- 16, and the foot pounds of work, W, and the horse power, H. P., absorbed per min- ute by the current of air in being moved, will be 60 px A v W = = 3.75 px A v (59) 16 3.75 px A v E. P. = = .000114 px A v (60) 33000 This formula may be stated in terms of the cubic feet of air discharged per minute. Take the relation between PJ> and ft w at 60 degrees as 12 p* = 16 X .433 h w ; also, A X v = 144 Q' when Q' = cubic feet of air discharged per second and, from formula (58), Jiw v 2 -4- 4356, then by substituting in formula 60 3.75 X .577 X v 2 X 144 Q' H. P. = : = .0000022 v 2 Q' (61) 4356 X 33000 APPLICATION 1. Let the effective area of a stream of dry air at 60 degrees, exhausting between the pressures of pa = PLENUM WARM AIR HEATING 155 \^/z ounces and po = % ounce, be 400 square inches. What is the work performed per minute and the horse power con- sumed? TF = 3.75 X (1% %) X 400 X .87 = 1305 foot pounds, and H. P. = .000114 X (1% %) X 400 X 87 = .1487. APPLICATION 2. A fan is delivering 1000000 cubic feet of air per hour to a heating system with a pressure of % ounce. What is the theoretical horse power of the fan? H. P. = .0000022 X (74. 5) 2 X 277 = 3.7 119. Actual Horse Power Consumed in Moving Air by Blower Fans: The theoretical horse power of a fan is that horse power necessary to move the air. This amount is al- ways exceeded, however, because of the inefficiency of the blower. Let E = efficiency of the blower, then formulas 60 and 61 become .000114 p x A v H. P. = (62) E .0000022 v* Q e H. P. = (63) E The value E varies with the peripheral velocity and the percentage of free outlet. When subjected to ordinary service, the efficiency of the fan or blower may vary any- where from 10 to 40 per cent. Probably a safe figure, for an efficiency not definitely known, is 30 per cent, for cen- trifugal fans in heating systems, (see also Art. 123.) 120. Carpenter's Practical Rules: Many experiments have been run upon blower fans to determine their capacity in cubic feet of air delivered per minute and to determine the horse power necessary to move this air. Probably as satisfactory as any are the rules quoted by Prof. Carpenter in H. & V. B., Art. 162, as follows: Rule. "The capacity of fans, expressed in cubic feet of air delivered per minute, is equal to the cube of the diam- eter of the fan wheel in feet multiplied by the number of revolutions, multiplied by a coefficient having the follow- ing approximate value: For fan with single inlet delivering air without pressure, 0.6; delivering air with pressure of one inch, 0.5; delivering air with pressure of one ounce, 0.4; for fans with double inlets, the coefficient should be in- creased about 50 per cent. For practical purposes of ven- tilation, the capacity of a fan in cubic feet per revolution will equal .4 the cube of the diameter in feet." Rule. "The delivered horse power required for a given 156 HEATING AND VENTILATION fan or blower is equal to the 5th power of the diameter in feet, multiplied by the cube of the number of revolutions per second, divided by one million and multiplied by one of the following' coefficients : For free delivery, 30; for de- livery, against one ounce pressure, 20; for delivery against two ounces of pressure, 10." The two above rules stated as formulas are as follows: where D = the diameter for pressure of one ounce, .5 . 6 for no pressure. Cu. ft. of air per min. C X R. P. M. in feet and C = (64) the, coefficient, .4 for pressure of one inch and D 5 (R. P, fif.) 3 X C H. P. = (65) 1000000 where C = 30 for open flow, 20 for one ounce and 10 for two ounces pressure respectively. These two rules may be checked up by sizes obtained from catalogs. They give, however, in ordinary calculations, very close approxima- tions. 121. If it is Desired to Obtain the Approximate Sizes of the Different Parts of the Fan \Vheel and Opening, the same can be found by the following table which gives good aver- age values for the standard makes of fans. For more com- plete data see tables in catalogs. TABLE XXIII. Diameter Wheel Diameter Inlet, Single Diameter Inlet, Double Dimensions of Exhaust Width of wheel at outer circumference Least radial distance from wheel to casing Maximum radial distance from wheel to casing D .66 D .5 D 6 D X .5 D to .08 D to .50 D to .5 D .6 D .16D 1. D to casing .50 D to 1. D Least side distance from wheel to casing. 05 D to . 08D Occupied Space of Full Housing Fan Discharge Vert. Discharge Horiz Length Width Height 1.7 D .7 D 1.5 D 1.5 D .7 D 1.7 D PLENUM WARM AIR HEATING 157 122. Fan Drives: Fans, for heating and ventilating purposes, may be driven by simple horizontal or vertical- throttling or automatic steam engines, or by electric mo- tors; the principal advantage of the latter being the clean- liness. In either case the power may be direct- connected or belt-connected to the fan. Direct-connected fans make a very neat arrangement, but they require slow speed engines or motors, occasionally making them so large as to be prohibitive. Where engines are used, any unusual noise or pounding in the parts is frequently carried through the fan to the air current and up to the rooms. Belted drives may run at higher speeds but they must of necessity be set off from the fan ten feet or more to get good belt contact. Noiseless chain drives will permit the same reductions of speed and will allow the engine to be set very close to the fan. Where a reduction is made in the space between the engine and the fan, it had best be made in the last named way. In deciding between an engine drive and a motor drive for use with steam coils, the amount of steam used in the engine should not be considered a loss, since this is all exhausted into the heater coils and is used instead of live steam from the boilers. An engine of high efficiency is not so essential either, unless the exhaust steam cannot be used. Enclosed engines running in oil are preferred when used on high speeds. The belt when used should, if pos- sible, have the tight side below to increase the arc of contact. Electric motors have more quiet action and in special cases should be specified. They would generally be speci- fied for installations where the exhaust steam could not be used, as in systems for ventilating only. This method of driving the fan is more satisfactory in many ways but its operation is usually more expensive. Direct current motors are desirable, whenever they can be applied, because of the convenience in obtaining changes of speed and because the motors may easily be direct-connected to the fan. Alter- nating current motors are used but they usually run at higher speeds, requiring reduction drives and are not so satisfactory in regulation. 123. Speed of the Pan: A blower fan, exhausting into the open air, will deliver air with a linear velocity slightly 158 HEATING AND VENTILATION below the peripheral velocity of the fan blades, but if this same fan be connected to a system of ducts and heater coils, the linear velocity of the air becomes much less be- cause of the increased resistance and the lag or slip that takes place between the fan blades and the moving air. In the average heating system this slip may be as great as 40 to 50 per cent. See Art. 119. It is customary, therefore, in applying blowers to heating systems, to consider the linear velocity of the air as it leaves the fan to be one- half that of the periphery of the fan blades. Since the velocity of the air upon delivery from the fan should not exceed 1800 to 2500 feet per minute, the outer point on the fan blades should not be expected to move faster than 3600 to 5000 feet per minute. Knowing this peripheral velocity, the revolutions per minute may be selected and the diameter obtained. In all direct-connected fans the revolutions per minute must agree with that of the engine or motor. In belted fans, however, this restriction need not apply. It is found that ordinary blower fans running at high speeds are very noisy and so practice has determined largely the number of rev- olutions to use. These may be taken as in the following table. TABLE XXIV. Speeds of Blower Fans in R. P. M. Diameter of wheel in inches Differential Pressures Va oz y 4 oz. loz. IK oz. 2 oz. 18 700 900 1100 1300 1500 24 650 700 825 1000 1150 86 400 500 575 675 800 48 300 375 400 500 600 60 225 290 340 400 475 72 175 230 290 340 40C 96 150 175 200 250 300 120 125 150 175 200 225 180 75 100 110 140 160 PLENUM WARM AIR HEATING 159 In some types of fans, the number of blades is in- creased and the depth of the blades is diminished, making the operation of the fan somewhat similar to that of the steam turbine. These fans take the name of turbine fana and from tests seem to show increased efficiency. As a result, this type of fan for the same work may be smaller for the same number of revolutions or it may be the same diameter and have a reduced speed. The above table does not apply to this type of fan, the speeds of which will average very closely to 70 per cent, of those in the table. 124. Size of the Engine: In obtaining 1 the size of the engine, it will be necessary first to assume the horse power. This had better be taken as a certain ratio to that of the fan. Probably a safe value would be H. P. of the engine = 3 H. P. of the fan (66) Having obtained the horse power of the engine, it will next be necessary to find the size of the cylinder. Let PI = the absolute initial pressure of the steam in the cylinder, i. e., atmospheric pressure + gage pressure, and r = number of the steam expansions in the cylinder, i. e., reciprocal of the per cent, of cut-off. The cut-off allowed for high speed engines in economical power service, approximates 25 per cent, of the stroke, but in engines for blower work this may be taken at 50 per cent, or half stroke. Find the mean effective pressure, PI, by the formula, 1 + hyperbolic logarithm of r P! = p a back pressure (67) r Next, let I = length of the stroke in inches and N = number of revolutions per minute and apply the formula 2p x I AN H. P. = (68) 12 X 33000 and find A, the area of the cylinder, from which obtain d, the diameter of the cylinder. In applying formula (68) it will b'e necessary to assume I, This, for engines operating blowers, may be taken, 2 I N = 200 to 400 Formula 67 assumes that the steam in the cylinder expands according to the hyperbolic curve, pv = p'v'. For values of hyperbolic or Naperian logarithms see Table 3, Appendix. 160 HEATING AND VENTILATION It also assumes no loss in the recompression of the steam in the cylinder. Both assumptions are only approximately correct, but the errors are slight and to a certain degree, tend to neutralize each other, hence the final results from this formula are near enough to be used for approximate calculations. For such work as this, r may be taken from 2 to 3, the former being probably pre- ferred. The back pressure should not be taken higher than, say, 5 pounds gage (19.7 pounds absolute), since this is determined by the pressure in the coils carrying exhaust steam. This pressure, in ordinary service, usually drops more nearly to atmospheric pressure. In finding the diameter and length of the stroke of the cylinder, it may be necessary to make two or more trial applications before a good size can be obtained. Owing to the fact that the initial steam pressure is frequently low, say not to exceed 40 or 50 pounds, the mean effective pressure is small, thus calling for a cylinder of large diameter. In such cases, the diameter of the cylinder may be greater than the length of the stroke. In cases, how- ever, where high pressure steam is used, say 100 pounds gage, the diameter of the cylinder would be less than the length of the stroke. APPLICATION 1. Assume the following to fit the design shown in Figs. 74, 75 and 76: good, dry steam from the boiler to the engine at 100 pounds gage pressure; direct- connected engine to fan, running at 200 revolutions per minute and delivering 2000000 cubic feet of air per hour to the building at one ounce pressure; steam cut-off in the cylinder at one-third stroke and used in the coils at 5 pounds gage pressure; find the sizes and horse powers of the fan and engine unit. Applying formulas (64), (65), (66), (67) and (68), 2000000 D. of fan = \l =7.5 feet. 60 X .4 X 200 (7.5) 5 X (3.3S) 3 X 20 H. P. of fan = = 10.2 1000000 H. P. of Engine = J X 10.2 = 13.6 / 1 + 1.0986 \ Pi = 115 I ) 19.9 = 60.5 pounds per 250 square inch. Now if 2 I N = 250, then I = = .625 feet = 400 PLENUM WARM AIR HEATING 161 13.6 X 12 X 33000 7.5 inches and A. = = 29 square 2 X 60.4 X 7.5 X 200 inches = 6% inches diameter. The engine would be, say, 6% inches X 7V 2 inches, at 200 R. P. M. APPLICATION 2. Assuming the values as in application 1, excepting that the steam is taken from a conduit main under a pressure of, say, 30 pounds per square inch gage, that 2 I N = 300, and that the steam cut-off in the cylinder is at one-half stroke. Then, as before, D of fan = 7.5 feet; H. P. of fan = 10.2; and H. P. of the engine = 13.6; the mean effective pressure is, however, / 1 + .6931 \ Pi = 45 ( J 19.9 = 18. 2 pounds per sq. in. 13.6 X 12 X 33000 and A = = 82 square inches. 2 X 18.2 X 9 X 200 Size of the engine would be 10% inches X 9 inches, at 200 R. P. M. 125. Piping Connections around Heater and Engine: Where the fans are run by steam power it is considered best to reduce the pressure of the steam by a pressure re- ducing valve before allowing the live steam to enter the coils. Where this reduction is made to 5 pounds or below, it may be entered into the same main with the exhaust steam from the engine, if desired; the back pressure valve on the exhaust steam line providing an outlet to the at- mosphere in case the pressure, for some reason, should run above the 5 pounds allowable back pressure. If the value of the back pressure is increased much above 5 pounds, the efficiency of the engine is seriously affected. In many installations where the condensation from the live steam is desired free from oil, a certain number of coils, only, are tapped for exhaust steam and this condensation trapped to a waste or sewer, the other coils delivering to a receiver of some sort for boiler feed or other purposes as may be required. Every system should be fully equipped with pressure reducing valves, back pressure valves, traps and a sufficient number of globe or gate valves on the steam supply, and of gate valves on the returns to make the system flexible and responsive to varying demands, at the will of the operator. Figs. 72 and 73 show a typical plan and elevation for such 162 HEATING AND VENTILATION connections. Some engineers advocate lifting the returns about 20 or 30 inches as shown at A and B to form a wate* seal for each section, thus making them independent in their action. This, in some cases where the coils are very deep, would, no doubt, be a benefit. 3TBACH PRESS. VA'^VE k - !&=r===3 5 ==r=^^ 3EPARATOF1. CHECK BO/LER Fig. 72. ' * BACK PRCS3 VALVE ifPReSS.Rt CX 3TEAM L.IVF JT| c !t UJ o * Q "> w - 1 - 1 flg p Size of registers in inches Size of stack in inches. 1. . 1 H 51,520 74,200 40,185 57,876 2 322 18x20 13x13 2... 8 1H \% l l /2 1% 29,400 86,260 42,210 35,350 22,932 28,283 32,923 27,573 1 1 1 1 184 226 263 220 17x18 17x21 17x25 17x21 17x13 17x13 17x18 17x18 4... 5 6... 7 8... 1H \% \% 1(5,520 16,520 42,210 12,885 12,885 32,923 1 1 1 103 103 263 13x13 13x13 17x25 13x 8 13x 8 17x13 9 10 Totals. 344,190 268,466 11 \ I 1 /* \% VA \% 1V4 l l A 81,130 115,430 40,500 55,370 63,840 48,440 51,940 23,660 23,660 63,840 63,281 99,039 34,775 47,507 54,775 89,672 40,513 19,377 18,455 49,795 2 4 1 2 2 1 2 1 1 2 506 792 278 380 488 317 824 155 148 898 17x24 17x18 17x26 17x18 17x21 17x80 13x20 13x20 13x20 17x18 17x13 17x13 17x18 17x13 17x18 17x13 13x18 13x18 13x13 17x13 12... 126,973 44,583 60,907 70,224 50,862 10 10 10 10 5 13 14. . 15 16 17 18 24,843 5 19 20 Totals. 540,100 467,189 21... 22 23... 24 25 26 27 28. 29. 30 l 1 1 1 1 1 II A i 81,130 17,150 103,460 17,150 31,900 48,580 93,030 28,420 37,380 54,110 63,281 13,377 88,764 13,377 27,447 41,682 79,819 22,163 29,156 42,206 2 1 2 1 1 2 2 2 1 2 506 107 710 107 220 333 638 177 233 338 17x24 13x13 21x28 13x18 17x21 13x20 17x80 13x15 17x21 13x20 17x13 13x 8 17x13 18x 8 17x13 13x18 17x13 13x 8 17x18 13x13 113,800 10 35,189 53,438 102,333 10 10 10 Totals. 598,961 421,272 Vent registers taken same size as heat registers. For sizes of engine .fan, heater coils, etc., see applications under these heads. PLENUM WARM AIR HEATING 165 166 HEATING AND VENTILATION gs g 5? PS h=| kd |^JD^=J ' t=4"B" C .M M M Fig. 75. PLENUM WARM AIR HEATING 167 OQ M=J i^j ^T-^ UT w* =-: >=l ^LELJsa- >Jj o a st I Fig. 76. 168 HEATING AND VENTILATION REFERENCES. References on 3Iechanical Warm Air Heating. TECHNICAL BOOKS. Snow, Furnace Heating, p. 99. Monroe, Steam Heat. & Vent., p. 124. Carpenter, Heating and Ventilating Buildings, p. 333. Hub- bard, Power, Heating and Ventilating, pages 525 and 551. TECHNICAL PERIODICALS. Engineering Review. Ventilating and Air Washing Appar- atus installed in the Sterling-Welch Building,, Cleveland, O., Jan. 1910, p. 38. Steam Heat, and Vent. Plant Required for Addition to the Hotel Astor, New York, March 1910, p. 27. Heating and Ventilating Plant of the Boston Safe Deposit and Trust Company's Building, C. L. Hubbard, April 1910, p. 37. Heating and Ventilating Installation on the Burnet St. School, Newark, N. J., Jan. 1909, p. 20. Heating and Venti- lating the New Jersey State Reformatory, Sept. 1909, p. 27. Comparison of Heat, and Vent. Plants Installed in Chicago Schools and Buildings at Various Periods, T. J. Waters, June 1906, p. 14. Heating and Ventilating of Schools, F. G. McCann, June 1906, p. 11. The Heating and Ventilation of Schools, Dec. 1904, p. 1; March 1905, p. 4; Sept. 1905, p. 1; Oct. 1905, p. 5. Note: The last two articles taken together comprise a complete series of the heating and ventilating of the schools of New York City. Machinery. Fans, C. L. Hubbard, Oct. 1905, p. 49; Nov. 1905, p. 109; Dec. 1905, p. 165. Heaters for Hot Blast and Ventilation, C. L. Hubbard, March 1907, p. 353. The Heating and Ventilation of Machine Shops, C. L. Hubbard, Sept. 1907, p. 1. Heating and Ventilating Offices in Shops and Factories, C. L. Hubbard, Feb. 1910, p. 437. Pans, Machinery's Reference Series, No. 39. The Heat- ing and Ventilating Magazine. Figuring Flow of Air in Metal Pipes by Chart, B. S. Harrison, Dec. 1905, p. 1. Flow of Air in Metal Pipes, J. H. Kinealy, July 1905, p. 3. Friction of Bends in Air Pipes, J. H. Kinealy, Sept. 1905, p. 1. A Test of Hot Blast Heating Coils, March 1905, p. 1. Simplifying the Installation and Operation of School Heating and Ventilating Apparatus, S. R. Lewis, July 1908, p. 10. A Rational For- mula Covering the Performance of Indirect Heating Surface, Perry West, March 1909, p. 1. Charts Showing the Perform- ance of Hot Blast Coils, B. S. Harrison, Oct. 1907, p. 23. The Engineering Magazine. Modern Systems for the Ventilation and Tempering of Buildings, Percival R. Moses, Feb. 1908. Do- mestic Engineering. Practical Suggestions about Blower Systems for Shop Heating, P. R. Still, Vol. 46, No. 4, Jan. 23, 1909 p. 100; Vol. 46, Jan. 30, 1909, p. 125. Trans. A. S. H. & V. E. Supplementing Direct Radiation by Fans, Vol. X, p. 286. Methods of Testing Blowing Fans, R. C. Carpenter, Vol. VI. p. 69. Some Experiments with the Centrifugal Fan, W. S. Monroe, Vol. V, p. 117. CHAPTER XII. MECHANICAL VACUUM, STEAM HEATING SYSTEMS. 127. In Addition to the Brief Discussion of vacuum steam heating as found in Arts. 66 and 67, it will be well to discuss more in detail the various systems by which this heating is accomplished. The advantages to be derived by the positive withdrawal of the air and the condensation from the radi- ators and pipes, compared to the natural circulation of the gravity system, are now too well established to need much discussion. Mains and returns that are too small, horizontal runs of piping that are unevenly laid so as to form air and water pockets, radiators that are only partially heated be- cause of the entrapped air, leaking air and radiator valves, radiators partially filled with condensation and all the accom- panying cracking and pounding throughout many of the grav- ity systems, are sufficient causes for the general public to demand a cure, if such cure can be found. One should not understand by this statement that every mechanical vacuum system is a cure for all the ills in the heating work, for even these systems may be improperly designed. The steam pipes may be too small to supply the radiators, although smaller pipes may be used in this than in the gravity work, the valves may be defective, or the vacuum specialties may be inefficient. Most of the defects in the average plant, however, are because of imperfections in that part of the system from the radiator to the boiler, and all of the first class vacuum systems are planned to meet just these conditions. Vacuum systems have other advantages over the gravity work, the principal one being that of lifting the return con- densation to a higher level. This is noticeable in the plac- ing of radiators or coils in basement rooms. Another very important advantage is in the laying out of the heating coils for. shop buildings and manufacturing plants. Low pres- sure gravity coils are limited to a length of about 75 feet. 170 HEATING AND VENTILATION Usually the condensation in a long coil of this kind is very great and requires extra heavy pressure on the steam end to circulate it. The steam follows the line of least resistance and forces the air out of certain pipes and permits it to re- main in others, the differential pressure not being great enough to eliminate all the air and heat the pipes uniformly. As a result of these conditions some of the pipes remain cold and ineffective as prime radiating surface. A vacuum sys- tem, with its positive circulation, increases the differential pressure, removes the air and gives uniform heating effect in coils that are several times as long as can 'be safely supplied by the gravity system. The accumulation of air in the radi- ators and coils is especially noticeable in systems vising ex- haust steam. When exhaust steam from engines or turbines is used in a gravity heating system, the back pressure is carried from atmospheric pressure to 10 pounds gage. With the ap- plication of the vacuum system it is possible to maintain this constantly at about atmospheric pressure. It is claimed by some, that it is possible to reduce the pressure in the radiators to such a degree that the pressure in the supply mains will fall considerably below atmosphere. No doubt the specialty Fig. 77. MECHANICAL, VACUUM HEATING 171 valves may be set so as to do this, but it would scarcely be considered an economical arrangement. The principal features of a mechanical vacuum system are shown in Fig. 77. Live steam is conducted to the engine and to the heating main, the latter through a pressure re- ducing valve to be used only when exhaust steam is insuf- ficient. The exhaust steam from the engines and pumps is conducted to the heating main and to the feed water heater. The exhaust steam line opens to the atmosphere through a back pressure valve which is set at the desired pressure for the supply steam. An oil separator shown on the exhaust steam line removes the oil and delivers it to an oil trap. At the entrance to the feed water heater, the exhaust steam passes through a series of baffle plates which remove the oil and entrained water from that part of the steam which enters the heater. A boiler feed pump and a vacuum pump, with the attending valves and governing appliances, com- plete the power room equipment. The steam supply to the heating system is piped to radiators and coils in the ordinary way, with or without temperature control. A thermostatic valve, or patented motor valve, is placed at the return end of each radiator and coil and these returns are then brought to- gether in a common return which leads to a vacuum pump or ejector. The return pipe and specialty valve for any one unit is usually y 2 inch. The combined return increases in size as more radiation is taken on. Horizontal steam mains usually terminate in a drop leg which is tapped to the return 8 to 15 inches above the bottom of the leg. Each rise in the system has a drop leg at the lower end of the rise. These points and all other points where condensation may collect are drained through specialty valves to the return. Water supply systems may be tapped for steam and return con- densation the same as any ordinary radiator. Steam is carried in the main at about atmospheric pressure, and just enough vacuum is maintained on the return to insure positive and noiseless circulation. In many cases where special lifts are required, these return systems are run under a negative pressure of 6 to 10 inches of mercury. Under such con- ditions water may be lifted from 6 to 10 feet. Either closed or opened feed water heaters may be used with the layout as given. Fig. 78 shows a section through the Marsh vacuum pump which represents a type very generally used in this work. 172 HEATING AND VENTILATION It will be noticed that this pump has a steam operated valve. The automatic governing feature of this valve tends to equal- ize the cylinder pres- sure to meet the vary- ing resistance in the main return of the heating system. Such a pump is handling alternately solid wa- ter and vapors, hence there is great ten- dency of the ordinary pump to race and pound at such times. In its operation the steam enters at A and passes into the space B through the annu- lar opening C be- Fig. 78. tween the reduced neck of the valve and the bore of the first chest wall. It is thus projected against the inside surface of the valve head before entering into the port and passing to the cylinder. On reaching the cylinder and driving the piston to the right, the reaction of the steam through port D to the opposite side of the valve head, tends to further open the steam port G. The valve then holds a position depending upon the relative strength of the forces which tend to move it in opposite directions, i. e., admission steam which tends to close the valve, and the cylinder steam which tends to open the valve. This is the governing feature. It will be noticed that the pump piston is in two parts and carries steam at admission pres- sure upon the inside. This steam is admitted along the dotted line to the center of the cylinder head, thence through a small tube and packing box to the hollow piston rod, which has a direct connection with the center of the piston. When the piston has moved sufficiently to bring the central space E in line with the duct D, steam is admitted to the right of the piston valve thus forcing it back, cutting off the steam at C, opening up the exhaust to the atmosphere through F and admitting steam to the other end of the cylinder. The action is thus reversed and continuous. Ejectors operated by steam, MECHANICAL VACUUM HEATING 173 water and electricity are also used to produce a vacuum. No comparison is made here of the various systems of pro- ducing vacuum since each gives satisfaction when properly installed. In each case there is a loss of energy but this loss is amply repaid in the added benefits. Several patented systems of mechanical vacuum heating are now upon the market. These are in large measure an outgrowth of the original Williames System, patented in 1882. Each system is well represented by the above diagram in all particulars concerning the steam and water circu- lation. The chief difference between them is in the thermo- static or motor connection at the entrance to each individual return. 128. Webster System: In this system a pump is used to produce the vacuum. A special fitting, called a water-seal motor, is used on all radiators, coils and drainage points. Fig. 79 shows a section of one of the valves. Other models are constructed so as to have the outlet in a horizontal di- rection, either parallel with or 90 degrees to the inlet. Jig. 80 shows an application of this to a radiator or coil. The dirt strainer is usually placed between the radiator or coil and ^HL C Fig. 80. the motor valve. This strainer collects the dirt and pro- tects from clogging the motor valve. C attaches to the re- turn end of the radiator or coil and L leads to the vacuum pump. O is the central tube, the lower end of which is a valve. A is a hollow cylindrical copper float, the central tube 174 HEATING AND VENTILATION of which fits loosely over spindle B. The function of the cylinder A is to raise the tube G from the seat H and open the discharge to the pump. Ordinarily, the float is down and the central tube valve is resting- upon the seat and cuts off communication with the radiator, excepting as air may be drawn from the radiator down the central tube around the spiral plug. The water of condensation accumu- lating in the radiator or coil passes into the chamber E, sealing the valve, and when sufficient water has accumulated to lift the float, it opens a passageway for a certain amount of the water to be withdrawn to the return. When this water becomes lowered sufficiently, the valve again seats itself and the cycle is completed. This action continues as long as water is present in the radiator. These motor valves are made of three sizes, y 2 inch, % inch and 1 inch. The first is the standard size and has a capacity of approximately 200 feet of radiation. Fig. 81 shows a ther mo static valve for many years in use by this Company and lately replaced by the above motor valve. It will be seen that the automatic feature in this valve is the compound rubber stalk, which expands and contracts under heat and cold. The adjusting screw at the top permits the valve to be set for any conditions of temperature and pressure within the radiator. The water of condensation passes through a screen and surrounds the rubber stalk. The temperature of the water being less than that of steam, the stalk contracts and the water is drawn through the opening A by the action of the pump. As soon as the water has been removed, steam flows around the stalk and ex- pands it until it closes the seat. This process is a continuous one and auto- matically removes the water from the radiator. The screen serves the purpose of the dirt strainer as mentioned above. A suction strainer, which is very similar to the dirt strainer only larger in capacity, is placed upon the return line next the pump. This fitting usually has a cold water connection to be used at times to assist in producing a more perfect Fig. 81. OF A LI FOB? ]CHANICAL VACUUM HEATING 175 vacuum. The piping system for the automatic control of the vacuum pump is shown in Fig. 82. It will be seen that the vacuum in the return operates through the governor to regu- late the steam supply to the pump cylinder, thus controlling the speed of the pump. Occasionally it is desirable to have certain parts of the heating system under a different vacuum. An illustration of this would be, where the radiators within the building were run under a neg- ative pressure of about one pound, and a set of heating coils Fig. 82. in the basement were to be carried under a negative pressure of four pounds. The Web- ster iSystem, type D, Fig. 83, meets this condition. The exact difference be- tween the suction pressure and the pressure in the radiators can be varied to suit any condition by the controller valve. A trap and a controller valve should be applied to each line having a different pressure from that in the suction line. A modulation valve, for graduating the steam supply to the radiator, has been designed by this Company and may be applied to any Webster Heating System to assist in its regulation. This modulation valve serves to graduate the steam supply to the radiators so that the pressure may be maintained at any point to suit the required heat loss from the building. 129. VamAuken System: In this system, as in the pre- vious one, the vacuum in the return main is produced by a vacuum pump which is controlled by an especially designed governor. The automatic valves which are placed on the radiators, coils and other drainage points along the system, are called Belvac Thermoflres, and are shown in section by Fig. 84. This valve is automatic and removes the water of 176 HEATING AND VENTILATION Fig-. 84. condensation by the controlling ac- tion of a float. It is connected to the radiator or coil at K and to the vacu- um return pipe at L. The water of condensation is drawn through the return pipe into chamber D until it reaches the inverted weir E which gives it a water seal. It is thence drawn upward into space D until it overflows into the float chamber AA, where it accumulates until the line of flotation is reached. When the float C lifts, the valve seat at B opens and allows the water 'to escape into the vacuum return pipe. After the removal of the w^ater the float again settles on seat B until sufficient water accumulates in the float chamber to again lift it, when the cycle is repeated. The air contained in the radiators or coils is drawn through the return and up through chamber D into the top of the float chamber. Here its direction follows arrows GO, being drawn through the small opening in the guide-pin at F, down through the hollow body of the copper float and valve seat B, into the vacuum return. This removal of air is continuous regardless of the amount of water present. The by-pass /, when open, allows all dirt, coarse sand or scale to pass directly into the vacuum return, thus cleaning the valve. By opening the by-pass /, only part way, the con- tents of chamber A may be emptied into the vacuum return without interfering with the conditions in space D. The ends of the float are symmetrical, hence it will work either way. The thermofires are made in four standard sizes of outlets, two having y 2 inch and two having % inch outlets. These valves have capacities of 125, 300, 550 and 1200 square feet of radiation respectively. Drop legs, strainers, governors and other specialties usually provided by such comipanies are supplied in addition to the thermofires. When a differential vacuum is to be ob- tained a special arrangement of the piping system is planned to cover this point. The piping connections around the auto- matic pump governor are the same as are shown in Fig. 82. MECHANICAL VACUUM HEATING 177 130. Automatic Vacuum System: In this system the automatic vacuum valve, which takes the place of the motor valve and thermofire in the two preceding systems, is shown in Pig. 85. K is the entrance to the radiator and L to the vacuum return. Screen V prevents scale and dirt from entering the valve. By-pass E is for emerg- \K ency use in draining off accumulated water and dirt, should the valve clog. With such an adjust- ment the bonnet of the valve may be removed for inspection without overflowing. Before the steam is turned on in the radiator the float is tipped, as shown in the figure, making a small wedge shaped opening through which the vacuum can pull on the radiator. When steam is admitted to the radi- ator, condensation flows into the valve, lifting the float and sealing the outlet against the passage of steam. As the valve continues to fill with water the float is lifted, and water passes to the vacuum return. As the water is drawn off the float falls and reseats on the nipple when about y 2 inch of water remains in the valve, thus maintaining the water seal. Fig. 86 shows the piping connections around the automatic pump gov- ernor. It will be seen that this connection differs from that of the Webster and Van Auken Systems, in that the pressure in the return main controls the flow of injection water into the Fig. suction strainer. 131. Paul System: Referring to Art. 67 it will be seen that the Paul System is essentially a one-pipe system, with the vacuum principle attached to the air valve. Its use is not restricted to the one-pipe radiator, since it may be applied 178 HEATING AND VENTILATION to the two-pipe radiator as well. The advantage to be gained, however, when applied to the former, is much greater than in the latter because of the greater possibility of air clog- ging the one-pipe radiator. This one fact has largely deter- mined its field of operation. This system differs from the ones just mentioned in two essential points; first, the vacu- um effect is applied at the air valve and the water of con- densation is not moved by this means; second, the vacuum effect is produced by the aspirator principle using water, steam or compressed air, as against the pumps used by the other companies. The same principle may also be applied to the tank receiving the condensation. By this means it is possible to remove all the air in the system and to produce a partial vacuum if necessary. Ordinarily the vacuum is supposed to extend only as far as the air valve at the radi- ator. If desired, however, this valve may be adjusted so that the vacuum effect may be felt within the radiator, and in some cases mlay extend into the supply main. Many modifications of the Paul System are being used. In its la- test development, the layout of the system for large plants, is Fig-. 87. MECHANICAL VACUUM HEATING 179 about the same as that shown in Fig 77, where all of the principal pieces of apparatus that go to make up the power room equipment are present. Fig. 87 shows a typical vacuum connection between one-pipe and two-pipe radiators and the exhauster. This diagram shows the discharge leading to a tank, sewer or catch basin. If exhaust steam were used, the discharge would probably lead into the steam supply to one or more of the radiators and then into the atmosphere. Where electric current can be had this exhausting may be done by the use of an electric motor. A specially designed thermostatic air valve is supplied by the Company to be used on this system. Other vacuum systems, each having a full line of specialty appliances, might be mentioned here but the above are con- sidered sufficient. 180 HEATING AND VENTILATION REFERENCES. References on Mechanical Vacuum Heating. TECHNICAL BOOKS. Snow, Principles of Heat., Chap. XL. Carpenter, Heating <& Vent. Blags., p. 285. Hubbard, Power, Heat. & Ventilation, p. 568. TECHNICAL PERIODICALS. Engineering Review. Steam Heating Installation in the Biology and Geology Building 1 and the Vivarium Building, Princeton University (Webster System), Jan. 1910, p. 27. Steam Heating and Ventilating Plant Required for Addition to Hotel Astor (Paul System), March 1910, p. 27. Heating Four Store Buildings at Salina, Kan., (Moline System, vacuum vapor), April 1910, p. 45. Steam Heating System for Henry Doherty's Mill, Paterson, N. J., May 1910, p. 37. Heating Residences at Fairfield, Conn., (Bremen's System of Vapor Heating), June 1910, p. 52. Heating Residence at Fleming- ton, N. J., (Vapor- Vacuum System), July 1910, p. 43. Heating System installed in the Haynes Office Building, Boston, (Web- ster Modulation System), Aug. 1910, p. 44. Heating the Silversmith's Building, New York, (Thermograde System), Jan. 1908, p. 8. Heating System in the New Factory of Jen- kins' Bros., Ltd., Montreal, Canada (Positive Differential System), Dec. 1907, p. 14. The Railway Review. Vacuum Ventila- tion for Street Cars, Oct. 23, 1909, p. 948. CHAPTER XIII. DISTRICT HEATING OR CENTRALIZED HOT WATER AND STEAM HEATING. GENERAL. 132. Heating Residences and Business Blocks from a cen- tral station is a method that is being employed in many cities and towns throughout the country. The centralization of the heat supply for any district in one large unit has an advantage over a number of smaller units in being able to burn the fuel more economically, and in being able to re- duce labor costs. It has also the advantage, when in con- nection with any power plant, of saving the heat which would otherwise go to waste in the exhaust steam and stack gases, by turning it into the heating system. The many electric lighting and pumping stations around the country give large opportunity in this regard. Since the average steam power plant is very wasteful in these two particulars, any saving that might be brought about should certainly be sought for. On the other hand, however, a plant of this kind has the disadvantage in that it necessitates transmitting the heating medium through a system of conduits, which generally is a wasteful process. The failure of many of the pioneer plants has cast suspicion upon all such enterprises as paying investments, but the successful operation of many others shows the possibilities, where care is exercised in their design and operation. 133. Important Considerations in Central Station Heat- Ing: In any central heating system, the following consider- ations will go far towards the success or the" failure of the enterprise: First. There should be a demand for the heat. Second. The plant should be near to the territory heated. Third. There should be good coal and water facilities at the plant. 182 HEATING AND VENTILATION Fourth. The quality of all the materials and the instal- lation of the same, especially in the conduit concerning in- sulation, expansion and contraction, and durability, are points of unusual importance. Fifth. The plant must be operated upon an economical basis, the same as is true of other plants. Sixth. The load-factor of the plant should be high. This is one of the most important points to be considered in com- bined heating and power work. The greater the proportion of hours each piece of apparatus is in operation, to the total number of hours that the plant is run, the greater the plani. efficiency. The ideal load-factor is where all of the apparatus is running at full load all the time. The average conduit radiates a great deal of heat, hence, the nearer the plant to the heated district the greater the economy of the system. Likewise a location near a railroad minimizes fuel costs; and good water, with the possibility of saving the water of condensation from the steam; all serve to the increased economy of the plant. It is to be expected that even a well designed plant, unless safeguarded against ills as above suggested, would soon succumb to inevitable failure. Two types of centralized heating plants are in use, hot water and steam. Each will be discussed separately. In the discussion of either system, certain definite conditions will have to be met. First of all, there should be a demand in that certain locality for such a heating system, before the plant can be considered a safe investment. To create a de- mand requires good representatives and a first class resi- dence or business district. When this demand is obtained the plan of the probable district to be heated will first be platted and then the heating plant will be located. In many cases the heating plant will be an added feature to an al- ready established lighting or power plant and its location will be more or less a predetermined thing 1 . In addition to these material and financial features just mentioned, one must consider the legal phases that always come up at such a time. These relate chiefly to the franchise requirements that must be met before occupying the streets with conduit lines, etc. All of these considerations are a part of the one general scheme. DISTRICT HEATING 183 134. The Scope of the \Vork in Central Station Heating may be had from the following outline: { Exhaust Steam Heaters Live Steam Heaters CENTRAL STA- Hot Water Heating Heating Boilers by use of. I Economizers Injectors or TION HEATING Co-Mingle rs Exhaust Steam . Steam Heating. Live Steam In the hot water system the return water at a lowered tem- perature enters the power plant, is passed through one or more pieces of apparatus carrying live or exhaust steam, or flue gases, and is raised in temperature again to that in the outgoing main. From the above, a number of combinations of reheating can be had. Any or all of the units may be put in one plant and the piping system so installed that the water will pass through any single unit and out into the main; or, the water may be split and passed through the units in par- allel; or, it may be made to pass through the units in series. All of these combinations are possible, but not practicable. In most plants, two or three combinations only are provided. In the existing plants the order of preference seems to be, exhaust steam reheaters, economizers, heating boilers, inject- ors or co-minglers, and live steam heaters. All of the above pieces of reheating apparatus operate by the transmission of heat through metal surfaces, such as brass, steel or cast iron tubes, excepting the co-mingler, this being simply a barometric condenser in which the exhaust steam is condensed by the injection water from the return main, the mixture being drawn directly into the pumps. The objection to the tube transmission is the lime, mud and oil deposit on the tube surfaces, thus reducing the rate of transmission and requiring frequent cleaning. The ob- jections to the co-minglers are, first, that the pumjp must draw hot water from the condenser and second, that a certain amount of the oil passes into the heating line. With per- 184 HEATING AND VENTILATION fected apparatus for removing the oil, the co-mingler will no doubt supersede, to a large degree, the tube reheaters in hot water heating. In the steam system the proposition is very much simplified. The exhaust steam passes through one or more oil separating devices and is then piped directly to the header leading to the outgoing main. Occasionally a connection is made from tuis line to a condenser, such that the steam, when not used in the heating system, may be run directly to the condenser. These pipe lines, of course, are all properly valved so that the current of steam may easily be deflected one way or the other. In addition to this exhaust steam supply, live steam is provided from the boiler and enters the header through a pressure reducing valve. In any case when the exhaust steam is insufficient the supply may be kept constant by auto- matic regulation on the reducing valve. In selecting between hot water and steam systems the preference of the engineer is very largely the controlling factor. The preference of the engineer, however, should be formed from facts and conditions surrounding the plant, and should not come from mere prejudice. The following points are some of the important ones to be considered: First cost of plant installed. This is very much in favor of the steam system in all features of the power plant equip- ment, the relative costs of the conduit and the outside work being very much the same. Cost of operation. This is in favor of the hot water sys- tem because of the fact that the steam from the engines may be condensed at or below atmospheric pressure, while the exhausts from the engines in the steam systems must be carried from five to fifteen pounds gage, which naturally throws a heavy back pressure upon the engine piston. Pressure in circulating mains. This is in favor of the steam system. The pressure in any steam radiator will be only a few pounds above atmosphere, while in a hot water sys- tem, connected to high buildings, the pressure on the first floor radiators near the level of the mains, becomes very excessive. The elevation of the highest radiator in the circuit, therefore, is one of the determining factors. Regulation. It is easier to regulate the hot water system without the use of the automatic thermostatic control, since the temperature of the water is maintained according to a DISTRICT HEATING 185 schedule, which fits all degrees of outside temperature. When automatic control is applied, this advantage is not so marked. Returning the icater to the power plant. In most steam plants the water of condensation is passed through indirect heaters, to remove as much of the remaining heat as possible and is then run to the sewer. This procedure incurs a consider- able loss, especially in cold weather when the feed water at the power plant is heated from low temperatures. This point is in favor of the hot water system. Estimating charges for heat. This is in favor of the steam system since, by meter measurement, a company is able to apportion the charges intelligently. The flat rate charged for water heating and for some steam heating is in many cases a decided loss to the company. 135. Conduits: In installing conduits for either hot water or steam systems the selection should be made after determining, first, its efficiency as a heat insulator; second, its initial cost; third, its durability. Other points that must be accounted for as being very essential are: the supporting, anchoring, grading and draining of the mains; provision for expansion and contraction of the mains; arrangements for taking off service lines at points where there is little move- ment of the mains; and the draining of the conduit. Some conduits may be installed at very little cost and yet may be very expensive propositions, because of their in- ability to protect from heat losses; while, on the other hand, some of the most expensive installations save their first cost in a couple of years' service. Many different kinds of insulating materials are used in conduit work such as mag- nesia, asbestos, hair felt, wool felt, mineral wool and air cell. Each of these materials has certain advantages and under cer- tain conditions would be preferred. It is not the real purpose here to discuss the merits of the various insulators, because the quality of the workmanship in the conduit enters into the final result so largely. The different ways that pipes may be supported and insulated in outside service will be given, with general suggestions only. E ig. 88 shows a few of the many methods in common use. A very simple conduit is shown at A. This is built up of wood sections fitted end to end, then covered with tarred paper to prevent surface water leaking in and bound with straps. The pipe either is a 186 HEATING AND VENTILATION loose fit to the bore and rests upon the inner surface, or is supported on metal stools, driven into the wood or merely resting upon it. These stools hold the pipe concentric with the inner bore of the log. With much movement of the pipe endwise, from expansion and contraction, these stools should not be used unless they are loose and have a wide surface contact with the wood. A metal lining with the pipe resting directly upon it is considered good. The conduit is laid to a good straight run in a gravel bed and usually over a small tile drain to carry off the surface water, excepting as this drain is not necessary in sections where there is good gravel drainage. The insulation in A. is only fair. The air space around the pipe, however, is to be commended. B is an improvement over A and is built up of boards notched at the edges to fit together. The materials used, from the outside to the center, are noted on the sketch beginning with the top and reading down. This covering is in general use and gives good satisfaction from every standpoint. C shows a good insulation and supports the pipe upon rollers at the center of a line of halved, vitrified tile. The lower half of the tile should be graded and the pipe then run upon the rollers, after which it may be covered with some pre- pared covering and the remaining space next the tile filled with asbestos, mineral wool or other like material. D shows the same adapted to cellar work. Occasionally two pipes are run side by side, main and return, in which case large halved tiles may be used as in E, having large metal supports curved on the lower face to fit the tile. If these supports are not desired the same kind of straight tiles may be used with a Tee tile inserted every 8 to 12 feet having the bell looking down as in F. In this bell is built a concrete setting with iron supports for the pipes which run on rollers, over a rod. These rollers are sometimes pieces of pipes cut and reamed, but are better if they are cast with a curvature to fit the pipes to be supported. This form of conduit, when drained to good gravel, gives first class service. G, H and / show box conduits with two or more thicknesses of % inch boards nailed together for the sides, top and bottom. The bottom of the conduit is first laid and the pipe is run. The sides are then set in place and the insulating material put in, after which the top is set and the whole filled in. 7 shows DISTRICT HEATING 187 Fig-. 88. 188 HEATING AND VENTILATION the best form of box, since with the air spaces this is a very good insulator. All wood boxes are very temporary, hence, brick and concrete are usually preferred. K is a conduit with 8-inch brick walls covered with flat stones or halved glazed tiles cemented to place to protect from sur- face leakage. The bottom of the conduit has supports built in every 8 to 12 feet, and between these points the conduit drains to the gravel. The usual rod and roller here serve as pipe supports. The pipe is covered with sectional cover- ing and the rest of the space may or may not be filled with wool or chips, as desired. L shows the sectional covering omitted and the entire conduit filled with mineral wool, hair felt or asbestos, and ashes. M has the supporting rod built into the sides of the conduit and has the bottom of the con- duit bricked across and cemented to carry the leaks and drainage to some distant point. N shows a concrete bot- tom with brick sides, having the pipe supported upon cast- iron standards. The latest conduit has concrete slabs for bottom and sides and has a reinforced concrete slab top. This conies as near being permanent as any, is reasonable in price, and when the interior is filled with good non-con- ducting material, or when the pipe is covered with a good sectional covering, it gives fairly high efficiency. All conduits should be run as nearly level as possible to avoid the formation of air pockets in the main. Any un- usual elevation in any part of the main may require an air vent being placed at the uppermost point of the curve, other- wise air may form in such quantities as to retard circulation. 136. Layout of Street Mains and Conduits: No definite information can be given concerning the layout of street mains, because the requirements of each district would call for independent consideration. The following general sug- gestions, however, can be noted as applying to any hot water or steam system: Streets to be used. Avoid the principal streets in the city, especially those that are paved; alleys are preferred because of the minimum cost of installation and repairs. Cutting of the Mains. Do not cut the main trunk line for branches more often than is necessary. Provide oc- casional by-pass lines between the main branches at the most important points in the system, so that, if repairs are being DISTRICT HEATING 189 made on any one line, the circulation beyond that point may be handled through the by-pass. Such by-pass lines should be valved and used only in case of emergency. Offsets and Expansion Joints. Offsets in the lines hinder the free movement of the water and add friction head to the pumps; hence, in water systems, the number should be re- duced to a minimum. Long radius bends at the corners re- duce this friction. Offsets are especially valuable to take up the expansion and contraction of the piping without the aid of expansion joints. This is illustrated in !E ig. 89, where anchors are placed at A, and the gradual bending of the pipes at each corner makes the necessary allowance. The expansion in wrought iron is about .00008 inch per foot per degree rise in temperature; hence in a hot water main the linear expansion between and 212 is .017 inch per foot of length or 1.7 inches for each 100 feet of straight pipe. In hot water heating systems, however, the temperature of thid pipe should never be less than, say, 50, which would cause an expansion from hot to cold of only .013 inch per foot, or 1.3 inches for each 100 feet of straight pipe. In a steam main the temperature may vary anywhere from 50 to 300, making a lineal expansion of .02 inch per foot of length or 2 inches for each 100 feet of straight pipe. As here shown the movement from the anchor at A toward B may be absorbed by the swinging of the pipe about O. B.B. should therefore be as long as possible, say one full block, to avoid unduly straining the pipe at the joints. Allowing a maximum movement of 6 inches for Fig. 89. each expansion joint, the anchors would be spaced 500 and 300 feet center to center respectively, fcr hot water and steam mains. These figures would seldom be exceeded, and in some cases would be reduced, the spacing depending upon the type of expansion joint used. Ordinarily, 400 feet spacing would be recommended for hot water and 300 feet for steam. If the city layout meets this value fairly well, then the expansion joints and anchors may be made to alternate with each other, one each to every city block. 190 HEATING AND VENTILATION Fig. 90. DISTRICT HEATING 191 A few of the expansion joints in common use are shown In Fig. 90. A is the old slip and packed joint. This joint causes very little trouble except that it needs repacking frequently. It is very effective when properly cared for. The slip joint should have bronze bearings on both the outside of the plug and the lining of the sleeve. The ends of the plug and sleeve may be screwed for small pipes, or flanged for large ones. B shows an improved type of slip joint, having a roller bearing upon a plate in the bottom of the conduit, and plugs bearing against metal plates along the sides of the conduit to keep it in line. G and D show other slip joints very similar to A and B. C has one ball and socket end to adjust the joint to slight changes in the run of the pipe, and D has two packings enclosing the plug to give it rigidity. The drainage in each case is taken off at the bottom of the casting. E has two large flexible disks fastened to the ends of the pipe and separated from each other by an annular ring casting. These disks are frequently corrugated, are usually of copper and are very large in diameter so that the pipe has considerable movement without endangering the metal in the disks. F has a corrugated copper tube fastened at the ends to the pipe flanges. This is protected from ex- cessive internal pressure by a straight tube having a sli- ding fit to the inside of the flanges, thus allowing for end movement. G is very similar to E. It has, however, only one copper disk. This disk is enclosed in a cast iron case- ment, one side of which is open to the atmosphere, the other side having the same pressure as within the pipe. H is very similar to E, having two copper diaphragms to take up the movement. These diaphragms flex over rings with curved edges and are thus protected somewhat against failure. I shows a copper U tube which is sometimes used. This is set in a horizontal position and the expansion and contraction is absorbed by bending the loop. In all these joints those which depend upon the bending of the metal require little attention except where complete rupture oc- curs. In old plants, however, the rupturing of these dia- phragms is of frequent occurrence. The packed joint re- quires attention for packing several times in the year, but very seldom causes trouble other than this. 192 HEATING AND VENTILATION Anchors. In any long run of pipe, where the expansion and contraction of the pipe causes it to shift its position very much, it is necessary to anchor the pipe at intervals so as to compel the movement toward certain desired points. The anchor is sometimes combined with the expansion joint, in which case the conduit work is simplified. See Fig. 91. Service pipes to residences are taken off at or near the anchors. All condensation drains in steam mains are like- wise taken off at such points. Fig. 91. Valves. All valves on water systems should be straight- way gate valves. Valves on steam systems should be gate valves on lines carrying condensation, and renewable seat globe valves on the steam lines. Valves should be placed on the main trunk at the power plant, on all the principal branch mains as they leave the main trunk, on all by-pass lines, on all the service mains to the houses, and at such important points along the mains as will enable certain portions of the heating district to be shut off for repairs without cutting out the entire district. DISTRICT HEATING 193 Manholes. Manholes are placed at important points along the line to enclose expansion joints and valves. These man- holes are built of brick or concrete and covered with iron plates, flag stones, slate or reinforced concrete slabs. Care must be exercised to drain these points well and to have the covering strong enough to sustain the superimposed loads. 137. Typieal Design for Consideration: In discussing dis- trict heating, each important part of the design work will be made as general as possible and will be closed by an application to the following concrete example which re- fers to a certain portion of an imaginary city, Fig. 92, as available territory. A city water supply and lighting plant is located as shown, with lighting and power units ag- gregating 475 K. W., city water supply pumps aggregating 3000000 gallons maximum capacity, and smaller units re- quiring approximately 15 per cent, of the amount of steam used by the larger lighting units, all as stated in gen- eral instructions. Chapter XVI. It is desired to redesign this plant and to add a district heating system to it; the same Fig. 92. 194 HEATING AND VENTILATION to have all the latest methods of operation and to be of such a size as to be economically handled. Fig. 99 shows the essen- tial details of the finished plant. , 138. Electrical Output and Exhaust Steam Available for Heating Purposes Prom the Power Units: In the operation of such a plant, one of the principal assets is the amount of exhaust steam available for heating purposes. The amount may be found for any time of the day or night by construct- ing a power chart as in Pig. 93, and a steam consumption chart as in Fig. 94. Referring to Fig. 93, the, values here ilA -- -- .". -ISA --" J - _-, l_ > 200 o ~v>y " P |IN .TO 1 V i- ^ .. - ^ ... / * 2. 1. / 1 -. 4 I " t A 1 * / a i / 1 ; / j , . I- > f *' ' t 3 '; / / / /* Pf Fig. 93. given are assumed, for illustration, to be those recorded at the switch board of the typical plant on a day when heavy service is required. The curves show that the 75 KW. unit runs from 12 P. M. to 7 A. M. and from 6 P. M. to 12 P. M. with an output of 25 KW. It also runs from 7 A. M. to 10 A. M. and from 4 P. M. to 6 P. M. under full load. The 150 KW. unit runs from 4 A. M. to 7 A. M. with an output of 100 KW. and then increases to 125 KW. for the entire time until 6 P. M. when it is shut down. The 250 KW. unit is started up at 7 A. M. and runs until 6 P. M. under full load, when the load drops off to 150 KW. and continues until 10 P. M. when the unit is shut down, leaving only the 75 KW. unit running. The heavy solid line shows all the power curves superimposed one upon the other. Having given the KW. output, the gen- DISTRICT HEATING 195 eral formula for determining the horse power of the engines is KW. X 1000 I. H. P. = (69) 746 X E X E' where E and E' are the efficiencies of the generator and en- gine respectively. If we assume the efficiency of the gener- ator to be 90 per cent., and that of the engine to be 92 per cent., then formula 69 becomes, KW. X 1000 /. H. P. = = approx, 1.62 KW. (70) 746 X .90 X .92 Assuming that the 250 KW. unit consumes 24 pounds, the 150 KW. unit 32 pounds, and the 75 KW. unit 32 pounds of steam per /. H. P. hour respectively, when running under normal loads, we have the total steam consumed in the three units at any time shown by the lower curve in Fig. 94. zzooo - i 1 ! H | -,-.-.. tut 1 8000 ^ o xooojj IOOOOQ ftT |p^f- rf liiajjMf^Ti {M b. YS 8000 R- __ at 3 PU VI B 4oco - 2000 ~ 4_ _j , !=^Tr rss; rn a.n n . f.n. p. HOURS. Fig. 94. The upper curve shows the 15 per cent, added allowance for the smaller units. The values assumed for efficiencies and the values for steam consumption are reasonable, and may be used if a more exact figure is not to be had. It will be seen that the maximum steam consumption in the generating units in the power plant is 23100 pounds per hour and the minimum is 1490 pounds per hour. These two 196 HEATING AND VENTILATION amounts, then, together with the exhaust steam from the circulating pumps on the heating system, if a hot water system is installed, and that from the pumps in the city water supply, will determine the capacity of the exhaust steam heaters on the hot water supply and the capacity of the boilers or economizers to be used as heaters when the exhaust steam is deficient. 139. Amount of Heal Available for Heating: Purposes in Exhaust Steam, Compared with That in Saturated Steam at the Pressure of the Exhaust: To study the effect of ex- haust steam upon heating problems and to determine, if possible, the theoretical amount of heat given off with the exhaust steam under various conditions of use, let us make several applications: first, to a simple high speed non condensing engine using saturated steam; second, to a compound Corliss non condensing engine using saturated steam; third, to the first application when superheated steam is used instead of saturated steam; and fourth, to a horizontal reciprocating steam pump. Assume the follow- ing safe conditions: Case one boiler pressure 100 pounds gage; pressure of steam entering cylinder 97 pounds gage; quality of steam at cylinder 98 per cent.; steam consump- tion 34 pounds per indicated horse power hour; one per cent, loss in radiation from cylinder; and exhaust pressure 2 pounds gage. Case 2 boiler pressure 125 pounds gage; pressure at high pressure cylinder 122 pounds gage; quality of steam entering high pressure cylinder 98 per cent.; steam consumption 22 pounds per indicated horse power hour; 2 per cent, loss in radiation from cylinders and re- ceiver pipe, and exhaust pressure 2 pounds gage. Case three same as case one with superheated steam at 150 de- grees of superheat; Case four as stated later. The number of B. t. u. exhausted with the steam, in any case, is the total heat in the steam at admission, minus the heat radiated from the cylinder, minus the heat ab- sorbed in actual work in the cylinder. High Speed Engine. Case One. Let r heat of vapor- ization per pound of steam at the stated pressure, 'a? = qual- ity of the steam at cut off, q heat of the liquid in the steam per pound of steam, and W 8 = pounds of steam per DISTRICT HEATING 197 indicated horse power hour. From this the total number of B. t. u. entering the cylinder per horse power hour is Total B. t. u. W s (xr + q) (71) From Peabody's Steam tables r = 881, x = .98 and q = 307; then if W a = 34, Initial B. t. u. = 34 (.98 X 881 + 307) = 39792.92. Deducting the heat radiated from the cylinder we have 39792.92 X .99 = 39395 B. t. u. per horse power left to do work. The B. t. u. absorbed in mechanical work (useful work + friction) in the cylinder per horse power hour is (33000 X 60) -H 778 = 2545 B. ne, formula 74, which is rec- ommended to be used in connection with (73), may be applied and the theoretical diameters found. (The approx- imate diameters and the friction heads need not be calcu- lated in (73) for use in (74) providing some estimate may be made for the value hf, for the various lengths of pipe. If desired, hf may be assumed without any reference to the diameter, but this is a rather tedious process. For good discussion of this point see Church's Hydraulic Motors, Art. 121.) $IQ d = .479/% X - (74) where d, hf, and I are the .same as in (73), and Q = cubic feet of water passing through the pipe per second. This formula differs from those given in the references stated, in that the term % is inserted as a mean value between the two extreme conditions, as stated in Art. 144. APPLICATION. Let it be desired to find the diameter for the single main between the power plant and A, Art. 144, with h f = 1.47 2 X .02 X 200 X (4.74) 2 V 5 d .479 ( - : ---- \ = 1 ft. = 12 in. ^ 3 X 1.47 ' Applying to the entire line with hf as given in next to last line of Table XXVII, gives power plant to A, d = 12 inches; A to B, d = 10 inches; B to C, d = 8 inches; C to D, d = 6 inches; and D to E, d = 4 inches. In some cases, when close estimating is not required, it is satisfactory to assume a velocity of the water and find the diameter without considering the friction loss. In many cases, however, this would soon prove a positive loss to the Company. With a .low velocity, the pipe would be large, the first cost would be large and the operating cost would be low. On the other hand, if the velocity were high, the pipe would be small, the first cost would be small and the operating cost and depreciation would be large. As an illustration of how the friction head in- creases in a pipe of this kind with increased velocity, DISTRICT HEATING . 207 refer to the run of mains between B and C. Assuming a velocity of 10 feet per* second, which in this case would be very high, the friction head, hf, for the single main, be- comes 62 and the theoretical diameter is 5.5, say 6 inches. The friction head, as will be seen, is 5.4 times the cor- responding value when the velocity was 5 feet per second. Since the pump must work continually against this head, it would incur a financial loss that would soon exceed the extra cost of installing larger pipes. It is found in plants that are in first class operation that the velocities range from 5 to 7 feet per second. The calculations in Arts. 144 and 145 are very much simplified by the use of the chart shown in the Appendix. In planning a system of this kind, find the friction head on the pumps and the diameters of the pipes for various velocities, say 4, 6, 8 and 10 feet per second. Estimate the probable first cost and the depreciation of the conduit system for each velocity, and balance these figures with the operating cost for a period of, say five years, to see which is the most economical velocity to use in figuring the system. 146. Service Connections are usually installed from 30 to 36 inches below the surface of the ground, and are in- sulated in some form of box conduit which compares favor- ably with that of the main conduit. Service branches are li/4, IVa and 2 inch wrought iron pipe. These are usually carried to the building from the conduit at the expense of the customer. Such branch conduits are not drained by tile drains. 147. Total Steam Available and B. t. u. Liberated per Hour for Heating the Circulating Water: The amount of steam available for heating the circulating water is that given off by the generating units, plus that from the cir- culating pumps, plus that from the city water supply pumps if there be any, plus that from the auxiliary steaming units in the plant, i. e., small pumps, engines, etc. In the typical application this amounts to 23100 + 12720 + 8680 = 44500 pounds per hour. This steam, of course, is not equal to good dry steam in heating value because of the work it has done in the engine 208 HEATING AND VENTILATION and pump cylinders, but a good estimate of its value may be approximated. In addition to the terms used in for- mula 71, let q' heat in the returning condensation per pound; then the heat available for heating- purposes per pound of exhaust steam is B. t. u. = xr + q q' (75) It is probably safe to consider the quality of the steam as 85 per cent, of that of good dry steam at the same pressure. Since the pressure of the exhaust from a non condensing engine, as it enters the heater, is near that of the atmosphere, and since the returning condensation is at a temperature of about 180, the total amount of heat given off from a pound of exhaust steam to the circulating water is B. t. u. = .85 X 969.7 + 180.3 (180.54 32) = 856, say 850. If Wt be the pounds of exhaust steam available, the total number of B. t. u. given off from the exhaust steam per hour is Total B. t. u. = 850 W a (76) Applying this to the typical power plant gives 850 X 44500 37825000 B. t. u. per hour. This amount is probably a maximum under the conditions of lighting units as stated, and would be true for only 5 hours out of 24. At other times the exhaust steam drops off from the lighting units and this deficiency must be made good by heating the circulating water directly from the coal, by passing the water through heating boilers or by passing it through economizers where it is heated by the waste heat from the stack gases. 148. Amount of Hot Water Radiation in the District that can be Supplied by One Pound of Exhaust Steam on a Zero Day: In Art. 141, each pound of water takes on 25 B. t. u. in passing through the reheaters at the power plant, and gives off at least 20 B. t. u. in passing through the radiator. The number of pounds of water heated per pound of steam per hour is, W v = (Total B. t. u. available per pound of exhaust steam per hour) -~ 25, and the total radi- ation that can be supplied is Total B.t.u. available per Ib. of exhaust steam per hr. R W (77) 8.33 X 25 DISTRICT HEATING 209 which for average practice reduces to 850 R w = =: 4 square feet approx. (78) 208 Applying- formula 77 for the five hour period when the exhaust steam is maximum gives R w 37825000 -^ 208 = 181851 square feet. It is not safe to figure on the peak load conditions. It is better to assume that for half the time, 35000 pounds of steam are available and will heat 35000 X 4 = 140000 square feet of radiation. 149. The Amount of Circulating; Water Passe*! through the Heater Necessary to Condense One Pound of Exhaust Steam is Total B.t.u. available per Ib. of exhaust steam per hr. Wv, (79) 25 With the value given above for the exhaust steam this becomes, for 100 and 85 per cent, respectively, 1000 W w = = 40 pounds (80) 25 850 W w 34 pounds (81) 25 150. Amount of Hot Water Radiation in the District tlisit can be Heated by One Horse Power of Exhaust Steara from a Non Condensing Engine on a Zero Day: R w = 4 X (pounds of steam per H. P. hour) (82) This reduces for the various types of engines, as follows: Simple high speed 4 X 34 = 136 square feet. " medium " 4 X 30 = 120 " " Corliss 4 X 26 = 104 Compound high " 4X26 = 104 " medium " 4 X 25 = 100 " Corliss 4 X 22 = 88 151. Amount of Radiation that can be Supplied by Ex- haust Steam in Formulas 77 and 78 at any other Temper- ature of the "Water, fw, than that stated, with the Room 210 HEATING AND VENTILATION Temperature, t', remaining the same: The amount of heat passing through one square foot of the radiator to the room is in proportion to t w t'. In formulas 77 and 78, t w V 100. Now if tw be increased x degrees, so that tw t f = (100 + x), then each square foot of radiation in the building 100 + x will give off times more heat than before and 100 each pound of exhaust steam will supply only 4 X 100 square feet (83) 100 + x This for an increase of 30 degrees, which is probably a max- imum, is 4 R w = = 3 square feet (84) 1.3 Compared with (78), formula 83 shows, with a high tem- perature of the water entering the radiator, that less radi- ation is necessary to heat any one room and that each square foot of surface becomes more nearly the value of an equal amount of steam heating surface. Calculations for radiation, however, are seldom made from high temper- atures of the water,' and this article should be considered an exceptional case. 152. Exhaust Steam Condenser (Reheater), for Reheat- ing the Circulating Water: In the layout of any plant the reheaters should be located close to the circulating pumps and on the high pressure side. They are usually of the surface condenser type, Fig. 97, and may or may not be installed in duplicate. Of the two types shown in the fig- ure, the water tube type is probably the more common. The same principles hold for each in design. In ordinary heaters for feed water service, wrought iron tubes of iy 2 to 2 inches WATET? TUBE TVPt WATEP STEAM TUBLTVPE Fig. 97. DISTRICT HEATING 211 diameter are generally used, but for condenser work and where a rapid heat transmission is desired, brass or copper tubes are used, having diameters of % to 1 inch. In heating the circulating water for district service, the reheater is doing very much the same work as if used on the condens- ing system for engines or turbines. The chief difference is in the pressures carried on the steam side, the reheater con- densing the steam near atmospheric pressure and the con- denser carrying about .9 of a perfect vacuum. In either case it should be piped on the water side for water inlet and out- let, while the steam side should be connected to the exhaust line from the engines and pumps, and should have proper drip connections to draw the water of condensation off to a condenser pump. This condenser pump usually delivers the water of condensation to a storage tank for use as boiler feed, or for use in making up the supply in the heating sys- tem. In determining the details of the condenser the following important points should be investigated: the amount of heating surface in the tubes, the size of the water inlet and outlet, the size of the pipe for the steam connection, the size of the pipe for the water of condensation and the length and cross section of the heater. 153. Amount of Heating Surface in the Reheater Tubes: The general formula for calculating the heating surface in the tubes of a reheater (assuming all heating surface on tubes only), is Total B. t. u. given up by the exhaust steam per hr R t = ( 85 ) K (Temp. diff. between inside and outside of tubes) The maximum heat given off from one pound of exhaust steam in condensing at atmospheric pressure is 1000 B. t. u., the average temperature difference is approximately 47 degrees, and K may be taken 427 B. t. u. per degree dif- ference per hour. In determining K, it is not an easy mat- ter to obtain a value that will be true for average practice. Carpenter's H. & V. B. Art. 47 quotes the above figure for tests upon clean tubes, and volumes of water less than 1000 pounds per square foot of heating surface per hour. It is found, however, that the average heater or condenser 212 HEATING AND VENTILATION tube with its lime and mud deposit will reduce the efficiency as low as 40 to 50 per cent, of the maximum transmission. Assume this value to be 45 per cent.; then if W a is the number of pounds of available exhaust steam, formula 85 becomes 1000 TF, 1000 W, 1000 W, W, Rt = _ (86) K(t, tw) 427 X .45 X 47 9031 9.1 In "Steam Engine Design," by Whitham, page 283, the following formula is given for surface condensers used on shipboard: W L S = CK (!,. where = tube surface, W = total pounds of exhaust steam to be condensed per hour, L = latent heat of saturated steam at a temperature T it K theoretical transmission of B. t. u. per hour through one square foot of surface per degree dif- ference of temperature = 556.8 for brass, c = efficiency of the condensing surface = .323 (quoted from Isherwood), TI = temperature of saturated steam in the condensers, and * average temperature of the circulating water. "With L = 969.7, c = .323, K = 556.8 and TI t 47, we may state the formula in terms of our text as 969.7 W* W* Rt = = = (87) .323 X 556.8 X 47 8446 8.7 In Sutcliffe "Steam Power and Mill Work," page 512, the author states that condenser tubes in good condition and set in the ordinary way have a condensing power equivalent to 13000 B. t. u. per square foot per hour, when the condensing water is supplied at 60 degrees and rises to 95 degrees at dis- charge, although the author gives his opinion that a trans- mission of 10000 B. t. u. per square foot per hour is all that should be expected. This checks closely with formula 86, which gives the rate of transmission 9031 B. t. u. per square foot per hour. The following empirical formula for the amount of heat- ing surface in a heater is sometimes used: R t = .0944 W s (88) Where the terms are the same as before. DISTRICT HEATING 213 APPLICATION. Let the total amount of exhaust steam avail- able for heating the circulating- water be 35000 pounds per hour, the pressure of the steam in the condenser be atmos- pheric and the water of condensation be returned at 180; also, let the circulating water enter at 155 and be heated to 180. These values are good average conditions. The assump- tion that the pressure within the condenser is atmospheric might not be fulfilled in every case, but can be approached very closely. From these assumptions find the square feet of surface in the tubes. 35000 Formula 86, R t = - = 3846 sq. ft. 9.1 35000 Formula 87, R t = - = 4023 sq. ft. 8.7 Formula 88, R t = 35000 X .0944 = 3304 sq ft. 1000 X 35000 Satellite R t = -- = 3500 sq. ft. 10000 If 3846 square feet be the accepted value it will call for three heaters having 1282 square feet of tube surface each. 154. Amount of Reheater Tube Surface per Engine Horse Power: Let tc s be the pounds of steam used per I. H. P. of the engine; then from formula 86 Rt (per /. H. P.) = - (89) 9.1 This reduces for the various types of engines as follows: Simple high speed 34 -=- 9.1 = 3.74 square feet " medium " 30 -J- 9.1 = 3.30 " Corliss 26 -T- 9.1 = 2.86 Compound high " 26 ^ 9.1 = 2.86 " medium " 25 -j- 9.1 = 2.75 " Corliss 22 -H 9. 1=2. 42 155. Amount of Hot Water Radiation in the District that can he Supplied by One Square Foot of Reheater Tube Surface: If the transmission through one square foot of 214 HEATING AND VENTILATION tube surface be K (t s w ) = 9031 B. t. u. per hour and the amount of heat needed per square foot of radiation per hour = 8.33 X 25 = 208, as given in formula 77, then 9031 R w (per sq. ft. of tube surface) = = 43 . 4 sq. ft. (90) 208 156. Some Important Reheater Details: Inlet and Outlet Pipes: Having three heaters in the plant, it seems rea- sonable that each heater should be prepared for at least one- third of the water credited to the exhaust steam. From Art. 148 this is 140000 -f- 3 = 46667 gallons = 10800000 cubic inches per hour. The velocity of the water entering and leaving the heater may vary a great deal, but good values for calculations may be taken between 5 and 7 feet per second. Assuming the first value given, we have the area of the pipe = 10800000 -f- (5 X 12 X 3600) = 50 square inches, and the diameter 8 inches. The Size of the Reheater Shell. Concerning the velocity of the water in the reheater itself, there may be dif- ferences of opinion; 100 feet per minute will be a good value to use unless this value makes the length of the tube too great for its diameter. If this is the case the tube will bend from expansion and from its own weight. At this velocity the free cross sectional area of the tubes, assuming the water to pass through the tubes as in Fig. 97, would be 150 square inches. If the tubes be taken % inch outside diam- eter, with a thickness of 17 B. W. G., and arranged as usual in such work, it will require about 475 tubes and a shell diameter of approximately 30 inches. If the inner surface of the tube be taken as a measurement of the heating surface and the total surface be 1282 square feet, the length of the reheater tubes would be approximately 16 feet. The ratio of the length of the tube to the diameter is, in this case, 256, about twice as much as the maximum ratio used by some manufacturers. It would be better therefore to increase the number rf tubes and decrease the length. With a velocity of the water at 50 feet per minute, the values will be approximately as follows; free cross sec- tional area of the tubes, 300 square inches; number of tubes, 950; diameter of shell, 40 inches; length of tubes, 8 feet. These values check fairly well and could be used. DISTRICT HEATING 215 The Size of the Exhaust Steam Connection. To calculate this, use the formula 144 g, - (91) where y the additional heating boilers thrown into service. On the basis of 35000 pounds per hour, the exhaust steam and the stack gases together would heat 170960 square feet and there would be left 13540 square feet (184500 20 X 1548 4 X 35000), to be heated by additional boilers. Under minimum load this would be approximately 122500, leaving 62000 square feet to be heated by additional boilers. If one boiler horse power will supply 160 square feet of radiation, then it would require 84 and 387 boiler horse power re- spectively to supply the deficiency and the total horse power needed in each case would be 1632 and 1935. A more satis- factory analysis, however, is the following which is worked on the lasis of 44500 pounds per hour. DISTRICT HEATING 229 Let Ws = total number of pounds of steam used in the plant per hour = approximate number of pounds of exhaust steam available for heating the circulating water per hour; We = equivalent number of pounds of steam evaporated froir> and at 212; \ = total heat, above 32, in one pound of dry steam at the boiler pressure; q 1 = total heat, above 32, in one pound of feed water entering the boiler; then, if the latent heat of steam at atmospheric pressure = 969.7 B. t. u., we have W* (A a 1 ) We = (101) 969.7 and the corresponding boiler horse power needed as steam' ing boilers will be We B S H. P. = (102) 34.5 Next, the radiation in the district that can be supplied by the exhaust steam is Rw = 4 W s , and the amount sup- plied by the economizer is Re = 20 X B. H. P. From which we may obtain the capacity of the heating boilers as, Total Radiation 4 W s 20 B. H. P. Bw H. P. = (103) 160 The total boiler horse power of the plant is, therefore, the sum of B s H. P. and B w H. P. To obtain formula 103 for any specific case one must consider the maximum and minimum conditions of the steaming boiler plant. Let W s (max) maximum exhaust steam, and W s (min) = minimum exhaust steam. Then for the two following conditions we will have, Case 1, where the steaming and heating boilers are independent of each other, the total boiler horse power installed == B s H. P. + [total radiation 4 W s (min) 20 X 7?. H. P. in use] + 160; Also, Case 2, where a part or all of the steaming boilers are piped for loth steaming and water service, the total boiler horse power installed = B s H. P. + [total radiation 4 W s (max) 20 X B. H. P. in use] -j- 160. It will be noticed that the last term representing the economizer service is simply stated as boiler horse power and no distinction is made between steaming or heating service. This term will be difficult to estimate to an exact figure because it should be the total horse power in use at any one time, both steaming and heat- ing, and this can only be obtained by approximation. It makes no difference what service the boiler may be used for, the work of the economizer would be practically the same. 230 HEATING AND VENTILATION Probably the most satisfactory way is to substitute the value B a H. P. for B. H. P. in the economizer and get the approxi- mate total horse power, then if this approximate total horse power differs very much from that actually needed, other trials may be made and new values for the total horse power obtained until the equation is satisfied. Application. Let W s = pounds of exhaust steam, ^ = 1191.8 (125 pounds gage pressure), and q' = 28 (feed water at 60); then when W B = 44500 W e = 53400 B s H. P. = 1548 184500 4 X 22890 20 X 1548 B w H. P. Case 1 = = 387 160 184500 4 X 44500 20 X 1548 B w H. P. Case 2 = = 153 160 This shows that there is an excess of waste heat in Case 2, making a total boiler horse power, Case 1, = 1935 and Case 2, = 1548. Investigating Case 1 to see what error was intro- duced by using 1548 in the economizer, we find approximately 800 horse power of steam boilers in use, and the total horse power to be 1187, which is about 360 horse power on the unsafe side. Substitute again and check results. Case 2 is reasonably close. In any case the most economical size of boiler plant to install in a plant requiring both steaming and heating boilers is one where at least a part, if not all, of the boilers are piped so as to be easily changed from one system to the other. By such an arrangement the capacity may be made the smallest possible. After obtaining the theoretical size of the plant, it would be well to allow a small margin in excess so that one or two boilers may be thrown out of commission for repairs and cleaning without interfering with the working of the plant. Case 2 seems to be the better arrangement. Assuming 1800 total boiler horse power we might very well put in six 300 H. P. boilers arranged in three batteries. 168. Cost of Heating from a Central Station (Direct Fir- ing) : It will be 'Of interest in this connection to estimate approximately the cost in supplying heat by direct firing to one square foot of hot water radiation per year from the average central station. In doing this make the boiler as- sumptions to be the same as Art. 163. Take coal at 13000 DISTRICT HEATING 231 Fig. Power Plant Layout. 232 HEATIXG AXD VEXTILATIOX R. t. u- per pound, 2000 pounds per ton, and a boiler effi- ciency of per cent. "Water enters the boiler at 155 degrees from the returns, and is delivered to the mains at 180 de- grees. From the value of the coal as stated, we would have 15*0000 B. t. u. per ton given off to the water. This is equivalent to h eating- 24000 pounds, or 74&10 gallons, of water. If one ton of coal costs $2.00 at the plant, we have 200 -j- 74S10 = .0027 cents This represents the amount paid to reheat one" gallon of water, or to supply one s-quare foot of heading surface one tour at an outside temperature of zero degrees. Take the average temperature for the seven cold months at 32 de- grees. This is the average for the coldest year in the twenty years preceding 1&10. as recorded at the U. S. Exp. Station, LaFayette. Indiana. "We then have an average difference between the inside and the outside temperatures in any residence of 7t 32 = 2S. This makes the formula for the heat loss. Art. 2*, reduce to 3S -E- 70 = .54 of its former value. Now, if it takes one gallon of water per square foot of radiation per hour under maximum conditions, we have for the seven months .54 X ! X Zb S. 24 = 2722 gal- lons of water needed for each square foot of radiation per each healing year. This is equivalent to 2722 y .0027 = 7.35 cents per square foot of radiation for the heating year of seren months. When the plant is working under the best conditions this figure should be reduced. It tian be done with boilers of a higher eJideaey than that stated, and it can be done by using a cheaper coal, both of which are possible in many 1C*. Cwrt of Hratfms from a Oatral Station, f Tests: The following tests were conducted upon the Merchants R^atfng and Lighting Plant, LaFayette, Ind.; one in 19M and the other in 1M8. The plant was changed slight- ly between the two tests and the radiation carried upon the liaes was much increased, although tm all essential features the pHsit was the Miar. The circulating water was heated by rmhsast steam beaters and by heating boilers. The plant had the following important pieces of appara- tus employed hi grarisliag or absorbing the heat supply: DISTRICT HEATING 233 BOILERS (Steaming and Heating). Two 125 11. P. Stirling boilers. Total heating surface 2524 sq. ft. Three 250 H. P. Stirling boilers. Total heating surface 7572 sq. ft. Pressure on steaming boilers (gage), 150 Ibs. Pressure on heating boilers (approx.), 60 Ibs. ENGINES. One 450 H. P. Hamilton Corliss comp. engine, direct con- nected to a 300 K. W. Western Electric 72-pole alternating current generator 120 R. P. If. This engine carried the load of the plant when it was above 50 K. W., which was generally from 5:30 A. M. to 11:30 P. M. When this unit was run, direct current was obtained by passing the alternating current through a motor generator set. One 125 H. P. Westinghouse comp. engine, belted to one 75 K. W. 3-phase alternating and two direct current genera- tors, and run at 312 R. P. M, This unit was generally run between 11:30 P. M. and 5:30 A. ivi. One 250 H. P. Westinghouse comp. engine, belt connected to a 200 K. W. generator and two smaller machines. PUMPS. One centrifugal, two-stage pump, Dayton Hydraulic Co., direct connected to a Bates vertical high speed engine at 300 R. P. M. Two Smith-Vaile horizontal recip. duplex pumps 14 in. X 12 in. X 18 in. Each of the three pumps connected to the return main in such a way as to be able to use any combina- tion at any one time to circulate the water. The centrifugal pump had been in service only one season. It had a capacity about equal to the two reciprocating pumps and under the heaviest service this pump and one of the duplex pumps were run in parallel. One Smith-Vaile horizontal reciprocating tank pump 6 in. X 4 in. X 6 in. to lift the water of condensation from the exhaust heater to the tank. One Smith-Vaile horizontal reciprocating make-up pump 6 in. X 4 in. X 6 in. to replace the water that was lost from the system. 234 HEATING AND VENTILATION Two National horizontal reciprocating boiler feed pumps. One 9% in. Westinghouse air pump, to keep up the supply of air through the conduits to the regulator system in the heated buildings. One Deane vertical deep well pump, to deliver fresh water to the supply tank. One Baragwanath exhaust steam heater or condenser, having 1000 sq. ft. of heating surface. PARTIAL SUMMARY OF RESULTS. 1906 1. Square feet of radiation 118000 2. Temperature of circulating water in degrees F.-, flow main 158.36 3. Temperature of circulating water in degrees P., return main 139.9 4. Temperature of circulating water in degrees F., after leaving heater 145.6 5. Temperature of outside air in de- grees F 32.6 6. Temperature of stack gases in de- grees F., steaming boiler 7. Temperature of stack gases in de- grees F., heating boiler 562. 8. Draft in stacks (all boilers averaged) in inches of water . 68 9. Heating value of coal in B. t. u. per pound 12800 10. B. t. u. delivered to steaming boiler per hour by coal .18187000 11. B. t. u. delivered to heating boilers per hour by coal 19226000 12. B. t. u. delivered to circulating water by heating boilers per hour 11800000 13. B. t. u. to be charged to heating boil- ers (Item 12 Item 15) 7650000 14. B. t. u. delivered to circulating water by exhaust steam from tne gener- ating engines per hour 3600000 1908 150000 DISTRICT HEATING 235 15. B. t. u. thrown away during test from pump exhausts and available for heating- circulating water 4150000 8471000 16. B. t. u. available for heating- circu- lating water from all exhaust steam as in normal running (Item 14 + Item 15) 7750000 15073000 17. Total B. t. u. given to circulating water per hour (Item 13 + Item 16) . .15400000 22007000 18. Gallons of water pumped per hour [Item 17 (8.33 X Items 2-3)] 100000 108000 19. Gallons of water pumped per square foot of radiation per hour (Item 18 -^ Item 1) .85 .70 20. Efficiency of heating boilers (Item 12 -~ Item 11) approx .60 .55 21. Value of the coal in cents per ton of 2000 pounds at the plant 200. 175. 22. Average electrical horse power 68 141 Note. The above values are averages and were taken for each entire test. The B. t. u. values were considered sat- isfactory when approximated to the nearest thousand. 170. Regulation: The regulation of the heat within the residences is best controlled from the power plant. In most heating plants a schedule is posted at the power house which tells the engineer the necessary temperature of the circu- lating water to keep the interior of the residences at 70 degrees with any given outside temperature. In other heat- ing plants the regulation is by means of air carried from the compressor at the power house through a main running parallel with the water mains in the conduits and branching to each building where it is used under a pressure of 15 pounds to operate thermostats, which in turn control the water inlets to the radiators. A closer regulation is ob- tained in the latter system than in the former, but it is needless to say that the thermostats require careful adjust- ments and frequent inspections. 236 HEATING AND VENTILATION STEAM SYSTEMS. 171. Heating by steam from a central station, compared with hot water heating, is a very simple process. The power plant equipment is composed of a few inexpensive parts, the operation of which is very simple and easily explained. These parts have but few points that require rational de- sign. Because of the simplicity and because of the similarity to the preceding discussion on hot water systems, the work on steam systems will be very brief. All questions referring to the construction of the conduit, the supporting of the pipes, the provision for contraction and expansion, the drain- ing of the pipes and the draining of the conduits, are com- mon to both hot water and steam systems and are discussed in Arts. 135 and 136. A large part of the work referring directly to district hot water heating applies with almost equal force to steam heating. This part of the work, there- fore, will deal with such parts of the power plant equipment as differ from those of the hot water system. 'Steam heating may be classified under two general heads, high pressure and low pressure. A very small part, only, of the heating in this country is now done by what may be strictly called high pressure service, i. e., where radiators or coils are under pressures from 30 to 60 pounds gage, and this small amount is gradually decreasing. Ordinarily, steam is generated at high pressure at the boiler, 60 pounds to 150 pounds gage, and reduced for line service to pressures vary- ing from to 30 pounds gage, with a still further reduction at the building to pressures varying from to 10 pounds gage, for use in radiators and coils. Where exhaust steam is used in the main, the pressure is not permitted to go higher than 10 pounds gage, because of the back pressure on the engine piston. Where exhaust steam is not used, the pres- sures may go, as high as 30 pounds gage, thus allowing for a greater pressure drop in the line and a corresponding re- duction in pipe sizes. The principles involved in the power plant end of a steam heating system may be represented by Fig. 100. It will be seen that the exhaust steam from the engines or tur- bines has four possible outlets. Passing through the oil : separator, which removes a large part of the entrained oil, i part of the exhaust steam is turned into the heater for use in i DISTRICT HEATING 237 heating the boiler feed water. The rest of the steam passes on into the heating system. If there be more exhaust steam than is necessary to supply the heating system, the balance may go to the atmosphere through the back pressure valve. When the heating system is not in use, as would be the case in the four warm months of the year, the exhaust steam may be passed into the condenser. Fig. 100. It is very evident, from what has been said before, that it would not be economical to condense the steam in a con- denser as long as there is a possibility of using it in the heating system. The increased gain in efficiency, when con- densing the exhaust steam under vacuum, is very small com- pared to the gain when this same steam is used for heating purposes. It would also be very poor economy to use any live steam for heating when there were any exhaust steam wasted. When the amount of exhaust steam is insufficient, live steam is admitted through a pressure reducing valve. 172. Drop in Pressure and the Diameter of the Mains: The flow of steam in a pipe follows the same general laws as the flow of water. The loss of head may be represented by the well known formula Ji f = (104) 9d where hf = loss of head in feet, < = coefficient of friction, v = velocity in feet per second, I length of pipe in feet, 238 HEATING AND VENTILATION d = diameter of the pipe in feet and g = 32.2. Substitute, hi = 144 p -+- D, where p = drop in pressure in pounds and D = den- sity of the steam, and find 2 lv 2 P = (105) 144 gd The coefficient of friction is found to vary with the velocity of the steam and with the diameter of the pipe. Prof. Unwin found, that for velocities of 100 feet per second (good prac- tice for transmission lines), it could be expressed as follows, where c is a constant to be found by experiment, -\ ) 10 d ) which, when substituted in (105), gives lv 2 Dc 72 gd Let TF = pounds of steam passing per minute and efi = diam- eter of pipe in inches, then , = -_( + i ace, 1 / 3.6 \ W 2 lc P = ( 1 H ) (107) 20.663 \ di / d^D From this formula we may obtain any one of the three terms, W, d^ or p, if the other two are known. Table 31, Appendix, was compiled from (107) with c = .0027. For discussion, see Trans. A. S. M. E., Vol. XX, page 342, by Prof. R. C. Carpen- ter. Also Encyclopedia Britannica, Vol. XII, page 491. See also, Kent, page 670, and Carpenter's H. & V. B., page 51. It will be seen that Table 31 is compiled upon the basis of one pound pressure drop, at an average pressure of 100 pounds absolute in the pipe. Since, in any case, the drop In pressure is proportional to the square of the pounds of steam delivered per minute (other terms remaining constant), the amount delivered at any other pressure drop than that given (one pound) would be found by multiplying the amount given in the table by the square root of the desired pressure drop in pounds. Also, since the weight of steam moved at the same velocity, under any other absolute pressure, is ap- proximately proportional to the absolute pressures (other terms remaining constant), we have the amount of steam moved under the given pressure, found by multiplying the amount given in the table by the square root of the ratio of the absolute pressures. To illustrate the use of the table DISTRICT HEATING 239 suppose the pressure drop in a 1000 foot run of 6 inch pipe is 8 ounces, when the average pressure within the pipe is 10 pounds gage. The amount of steam carried per minute is 93.7 X V^5 -r V100 -T- 25 = 133 pounds. Or, if the drop is 4 pounds, at an average inside pressure of 50 pounds gage, the amount carried would be 150 pounds per minute. Con- versely find the diameter of a pipe, 1000 feet long, to carry 150 pounds of steam pe.r minute, at an average pressure of 10 pounds gage and a pressure drop of 8 ounces. 150 JfTHT" W (table) = X J = 264 poun ds V.5 ^ 65 which, according to the table, gives a 9 inch pipe. 173. Dripping: the Condensation from the Mains: The condensation of the steam, which takes place in the con- duit mains, should be dripped to the sewer or the return at certain specified points, through some form of steam trap. These traps should be kept in first class condition. They should be inspected every seven or ten days. No pipe should be drilled and tapped for this water drip. The only satisfactory way is to cut the pipe and insert a tee with the branch looking downward and leading to the trap. The sizes of the traps and the distances between them can only be determined when the pounds of condensation per running foot of pipe can be estimated. 174. Adaptation to Private Plants: District steam heat- ing systems may be adapted to private hot water plants by the use of a "transformer." This in principle is a hot water tube heater which takes the place of the hot water heater of the system. It may also be adapted to warm air systems by putting the steam through indirect coils and taking the air supply from over the coils. 175. General Application to the Typical Design: The following brief applications are meant to be suggestive of the method only and the discussions of the various points are omitted. Square feet of radiation in the district. R 8 = 184500 X 170 4- 255 = 123000 square feet. Amount of heat needed in the district to supply the radiation for one hour in zero weather. Total heat per hour = 123000 X 255 = 31365000 B. t. u. 240 HEATING AND VENTILATION Amount of heat necessary at the power plant to supply the radiation for one hour in zero weather. Assuming 15 per cent, heat loss in the conduit (this is slightly less than that allowed for the hot water two-pipe system, 20 per cent.), we have, 31365000 -=- .85 = 36900000 B. t. u. per hour. Total exhaust steam available for heating purposes. 1F S (max) = (23100 + 8680) X 1.15 36547 pounds per hour. W s (min) = ( 1490 -f 8680) X 1.15 = 11696 pounds per hour. Total B. t. u. available from exhaust steam per hour for heating. Let the average pressure in the line be 5 pounds gage and let the water of condensation leave the indirect coils in the residences at 140 degrees. We then have from one pound of exhaust steam, by formula 75, B. t. u. = .85 X 960 + 195.6 (140 32) 903.7 Assuming this to be 900 B. t. u. per pound, the total available heat from the exhaust steam for use in the heating system is, maximum total = 32892300 B. t. u. and the minimum total 10526iOn B. t. u. Square feet of steam radiation that can be supplied by one pound of exhaust steam at 5 pounds gage. tf s = 900 -r- (255 -f- .85) = 3. Total B. t. u. to be supplied by live steam. B. t. u. (max load) = 36900000 32892300 = 4007700 B. t. u. B. t. u. (min. load) = 36900000 10526400 = 26373600 B. t. u. Total pounds of live steam necessary to supplement the exhaust steam. Let the steam be generated in the boiler at 125 pounds gage. With feed water at 60 degrees Max. load = 4007700 -j- 1163.8 = 3444 pounds. Min. load = 26373600 -j- 1163.8 = 22661 pounds. Boiler horse power needed for the steam power units. As in Arts. 164 and 167, B s H. P. (max.) = 36547 X 1.2 -=- 34.5 = 1271. B s H. P. (min.) = 11696 X 1.2 -r- 34.5 = 407. Total "boiler horse power needed in the plant. Maximum load. B. H. P. (total) 1271 + (3444 X 1.2 4- 34.5) = 1391. It will be noticed that this total horse power is 157 horse power less than the corresponding Case 2 in Art. 167. This is accounted for by the fact that no steam is used up in work in the circulating pumps, also that the conditions of steam generation and circulation are slightly different. 1500 boiler horse power would probably be installed in this case. DISTRICT HEATING 241 Size of Conduit Mains. Let it be required to find the diameters of the mains system in Jig. 96 at the important points shown. Art. 144 gives the length of the mains in each part. Allow .3 pound of steam for each square foot of steam radiation per hour (this will no doubt be sufficient to supply the radiation and conduit losses). Try, first, that part of the line between the power plant and A, with an average steam pressure in the lines of about 5 pounds gage and a drop in pressure of iy 2 ounce per each 100 feet of run (approximately 5 pounds per mile). 25200 pounds per hour gives TF = 420. The length of this part of the line is 200 feet and the drop is 3 ounces, or .19 pound. TF (table) = 420 / /J9- X V 100 V . = 2158 pounds which gives a 15 inch pipe. Following out the same line, we have TABLE XXVIII. reasoning for all parts of the PPtoA AtoB BtoC CtoD DtoE Distance between points _ 200 500 1500 1500 500 Radiation supplied, sq. ft - 84000 57000 34000 19000 8000 Pressure-drop in pounds = p .19 .47 1.4 1.4 .47 Diameter of pipe in inches, by table 15 13 11 9 5 In general practice, these values would probably be taken 16, 14, 12, 10 and 6 inches respectively. Look up Table 30, Appendix, and check the above figures. 242 HEATING AND VENTILATION REFERENCES. References on District Heating. TECHNICAL BOOKS. Allen, Notes on Heating and Ventilation, p. 131. TECHNICAL PERIODICALS. Engineering Netcs. Comparison of Costs of Forced-Circula- tion Hot Water and Vacuum-Steam Systems, J. T. Maguire, Dec. 23, 1909, p. 692. Design of Hot-Water System with Forced-Circulation, J. T. Maguire, fc>ept. 2, 1909, p. 247. En- gineering Review. Determining Depreciation of Underground Heating Pipes, W. A. Knight, Jan. 1910, p. 85. Some Remarks on District Steam Heating, W. J. Kline, April 1910, p. 61. Toledo Yaryan System, A. C. Rogers, May 1910, p. 58. Some of the Factors that Affect the Cost of Generating and Dis- tributing Steam for Heating. C. R. Bishop, Aug. 1910, p. 56. Central Station Heating Plant at Crawf ordsville, Ind., B. T. Gifford, Dec. 1909, p. 42. Wilkesbarre Heat, Light and Motor Co., A Live Steam Heating Plant, J. A. White, July 1908, p. 32. The Heating and Ventilating Magazine. Schott Systems of Central Station Heating, J. C. Hornung, Nov. 1908, p. 19. Data on Central Heating Stations, Nov. 1909, p. 7. Cost of Heat from Central Plants, March 1909, p. 31. Steam Heating in Con- nection with Central Stations, Paul Mueller, Oct. 1909, p. 24; Nov. 1909, p. 1. A Modern Central Hot Water Heating Sta- tion, W. A. Wolls, July 1910, p. 15. Central Station Heating, F. H. Stevens, June 1910, p. 5. Domestic Engineering. Report of Second Annual Convention of the National District Heating Association at Toledo, O., June 1, 1910. Vol. 51, No. 11, June 11, 1910, p. 255. CHAPTER XIV. TEMPERATURE CONTROL IN HEATING SYSTEMS. 176. From tests that have been conducted on heating systems, it has been conclusively proven that there is less loss of heat from buildings supplied by automatic tempera- ture control, than from buildings where there is no such con- trol. A uniform temperature within the building is desir- able from all view-points. Where heating systems are oper- ated, even under the best of conditions, without such control, the efficiency of the system would be increased by its appli- cation. No definite statement can be made for the amount of heat saved, but it is safe to say that it is between 5 and 20 per cent. A building uniformly heated during the entire time, requires less heat than if a certain part or all of the building were occasionally allowed to cool off. When a building falls below normal temperature it requires an extra amount of heat to bring it up to normal, and when the inside temperature rises above the normal, it is usually lowered by opening windows and doors to enable the heat to leave rap- idly. High inside temperatures also cause a correspondingly increased radiation loss. E luctuations of temperature, there- fore, are not only undesirable for the occupants, but they are very expensive as well. 177. Principles of the System: Temperature control may be divided into two general classifications, small plants and large plants. The control for small plants, i. e., such plants as contain very few heating units, is accomplished by regu- lating the drafts by special dampers at the combustion cham- ber. This method controls merely the process of combustion and has no especial connection with individual registers or radiators, it being assumed that a rise or fall of temperature in one room is followed by a corresponding effect in all the other rooms. This method assumes that all the heating units are very accurately proportioned to the respective rooms. The dampers are operated through a system of levers, which system in turn is controlled by a thermostat. Fig. 101 shows a typical application of such regulation. 244 HEATING AND VENTILATION Fig. 101. This may be applied to any system of heat. In addition to the ther- mostatic control from the room to the damper, as has just been men- tioned, closed hot water systems and steam and vapor systems should have regulation from the pressure within the boiler to the draft. Oc- casionally in the morn- ing the pressure in either system may be- come excessive before the house is heated enough for the thermo- stat to act. With such additional regulation no hot water heater or steam boiler would te forced to a dangerous pressure. I ig. 102 shows a thermostat manufactured by the Andrews Heating Co., Minne- apolis. The complete regulator has in addition to this, two cells of open circuit battery and a motor box, all of which illustrate very well the thermostatic damper control. The thermostat operates by a differential expansion of the two different metals com- posing the spring at the top. Any change in temperature causes one of the metals to ex- pand or contract more rapidly than the other and gives a vibrating movement to the project- ing arm. This is connected with the batteries and with the motor in such a way that when the pointer closes the contact with either one of the contact posts, a pair of magnets in the motor causes a crank arm to rotate through 180 degrees. A flexible connection between this crank and the damper causes the damper to open or close. A change in temperature in the opposite direction makes contact with the other post and reverses the movement of the crank and damper. The movement of the arm between the contacts is very small thus TEMPERATURE CONTROL 245 making the thermostat very sensitive. No work is required of the battery except that necessary to release the motor. Occasionally it is desir- able to connect small heat- ing plants having only one thermostat in control, to a central station system. Fig. 103 shows how the supply of heat may be controlled by the above method. Fig. 104 shows the Syl phon Damper Regulator made by The American Radiator Co., and applies to steam pressure control. The longitudinal expansion of a corrugated brass or copper cylinder operates the damper through a sys- tem of levers. The longitu- dinal movement of the cyl- inder is small and hence the bending of the metal in the walls of the cylinder is very slight. This small movement is multiplied Fig. 104. 246 HEATING AND VENTILATION through the system of levers to the full amount necessary to operate the damper. A similar device is made by the same Company for application to hot water heaters. Temperature control in large plants, i. e., those plants having a large number of heating units, is much more complicated. In furnace systems this is very much the same as described under small plants, with additional dampers placed in the air lines. The following discussions, therefore, will apply to hot water and steam systems, and will be additional to the control at the heater and boiler as discussed under small plants. Fig. 105 shows a typical layout of such a system. Compressed air at 15 pounds per square inch gage is main- tained in cylinder, $, which is located in some convenient Fig. 105. place for the attendant. This air is car- ried to the thermostat, T*, on one of the protected walls in the room. Here it passes through a controlling valve and is then led to the regulating valve on the radiator. T-his air acts on the top of a rubber diaphragm as shown in Fig. 106 to close the valve and to cut off the sup- ply. When the room cools off, the con- Fig. 106. trolling valve at Tn cuts off the supply and opens the air line to the radiator. This removes the air pressure above the diaphragm and permits the stem of the TEMPERATURE CONTROL 247 valve to lift. On the opening of the valve the steam or water again enters the radiator and the cycle is completed. Fig-. 66 shows the application of the thermostatic control to the blower work. This shows the thermostat B and the mixing dampers, located at the plenum chamber, in the single duct system. The same general arrangement could be applied to the double duct system, with the dampers in the wall at the base of the vertical duct leading to the room. 178. Some of the Important Points in the Installation of such work are as follows. Each radiator has its own regu- lating valve. All rooms having three radiators or less are provided with one thermostat. Large rooms having four or more radiators have two or more thermostats with not more tuan three radiators to the thermostat. Where other mo- tive power is not available for the air supply, a hydraulic compressor is used. This compressor automatically main- tains the air pressure at 15 pounds gage in the steel supply tank. The main air trunk lines are galvanized iron, % and % inch in diameter, and are tested under a pressure of 25 pounds gage. All branch pipes are J /4 and % inch galvanized iron. All fittings on the % inch pipes are usually brass. Where flexible connections are made, this is sometimes done by armoured lead piping. Thermostats are usually provided with metallic covers, and are finished to correspond with the hardware of the respective rooms. Each thermostat is pro- vided with a thermometer and a scale for making adjust- ments. Each radiator is provided with a union diaphragm valve having a specially prepared rubber diaphragm with felt protection. This valve replaces the ordinary radiator valve. One of these valves is used on the end of each hot water radiator, one on each one-pipe steam radiator and two on each two-pipe low pressure steam radiator. This last condition does not hold for two-pipe steam radiators with mechanical vacuum returns, in which case patented special- ties are applied by the vacuum company. In such cases the supply to the radiator only is controlled. In any first class system of control, the temperature of the room may easily be kept within a maximum fluctuation of three degrees. 179. Some Special Designs of Apparatus: All temperature control work is solicited by Specialty Companies, each having a patented system. In the essential features these systems all agree with the foregoing general statements. The chief 248 HEATING AND VENTILATION difference is in the principle upon which the thermostat, TK, operates. Pig. 107 shows a section through the thermostat manu- factured by The Johnson Service Co., Milwaukee. The air comes from the supply tank through the pipe C and enters Fig. 107 the thermostat through the cut off valve E. D leads to the regulating valve at the radiator or damper. From the valve E the air is led up to F. F is attached to the stem G which passes up through the outlet H and carries the grooved head I. If F be moved up to the inside opening of H, it will close the opening and will open C to D. It is evident, since F is against H, this air cannot escape to the atmosphere, but passes to pipe D, thence to the regulating valve and closes the hot water or steam valve or damper. Should the valve F be again pushed to the right hand seat, the supply of compressed air will again be closed off, the opening H will be uncovered, the air that has been stored in the regulating valve escapes, and the valves that have been shut are thereby opened. From this it will be seen that as the air valve F is either to the right or left, the main valve will be opened or shut. The valve F is moved by the thermostat. When valve F TEMPERATURE CONTROL 249 is open the lead seat N is off the port M and a small amount of air from the line C leaks through. This leakage is slight and continues until N closes the port again. The real thermo- stat is the spring P Q. These are steel and brass strips brazed together in one piece. Because of a higher coefficient of expansion in the one than in the other, a change in room temperature causes N to move toward, or away from, the seat. As soon as the temperature of the room drops sufficient- ly, Q contracts more rapidly than P, and the port closes. The leakage air is then confined under the diaphragm K and its pressure increases until the lever W is forced out and valve F is closed. By the closing of valve F, as stated above, the air is exhausted from above the diaphragm in the regu- lating valve and the radiator opens. The saddle R can be adjusted so as to make the thermostat more or less sensi- tive. To set the thermostat for any desired temperature turn the adjusting post U until the pointer Y indicates the proper temperature on the diaphragm ring. The thermostat as here shown gives full movement to the valve, i. e., full open and full closed. Other forms for control are designed for graduated movement of dampers where used in blower systems. Fig. 108 shows a section through the pattern K thermo- stat, manufactured by the Powers Regulator Co., Chicago. This thermostat consists of a frame carrying two corrugated disks, brazed together at the circumference and containing a volatile liquid having a boiling point at about 50 degrees F. At a temperature of about 70 degrees, the vapor within the disks has a pressure of about 6 pounds to the square inch. This pressure varies with every change of temperature and produces variations in the total thickness at the center of the disks. The compressed air enters at H and passes into chamber N through the controlling valve J, which is normally held to its seat by a coil spring under cap P. Within the flange M is located an escape valve L upon which the point of the supply valve J rests. Valve L tends to remain open when permitted by reason of the spring underneath the cap. When the temperature rises sufficiently to cause the disks to in- crease in thickness and move the flange M, the first action is to seat the escape valve L, its spring being weaker than that above J. If the expansive motion is continued after 250 HEATING AND VENTILATION valve L is seated, the valve J is then lifted from its seat and compressed air flows into the chamber N. As the air accumulates in chamber N, it exerts a pressure upon the elastic diaphragm K in opposition to the expansive force of the disk. So, whenever there is sufficient pressure in N to balance the power exerted by the disks, the valve J returns Fig. 108. to its seat and no more air is permitted to pass through. If the temperature falls, the pressure within the disks be- comes less, the disks draw together and the over-balancing air pressure in N reverses the movement of the flange M and permits the escape valve L under the influence of its spring to raise from its seat, whereupon a portion of the air in N is discharged until the pressure in N becomes equal to the diminished pressure from the disks. Thus the pressure of the air in N is maintained always in direct proportion to the expansive power (temperature) of the disks. Port J connects with chamber N and leads to the diaphragm valve. This thermostatic valve controls the- regulator valve by a graduated movement and is used on the dampers for TEMPERATURE CONTROL, 251 blower work. Another form with maximum movement only is designed for steam systems. Fig. 109 shows sections through the positive movement and the graduated movement thermostats, as manufactured by The National Regulator Co., Chicago. In the left diagram air enters the thermostat through the tube C, passes up through the filter P to the port G, and from thence through to a similar tube D to the regulating valve at the radiator. G may be opened or closed according as the stem K controls Fig. 109. the lever O. The movement of lever is caused by the ex- pansion and contraction of the vulcanized rubber tube A. The adjusting screw J at the top is set to permit G to open and close at any desired temperature. When the temperature of the room rises above the normal temperature, tube A expands, the pressure from K is released, tube G opens and compressed air from the supply tank passes through to the regulating valve and shuts off the heat. Upon lowering the temperature in the room, tube A contracts, the pressure of K on block M becomes greater, the port G closes, the con- fined air in the tube D leading to the regulating valve is ex- 252 HEATING AND VENTILATION hausted to the atmosphere, and the heat is turned on. The screw S is set so as to allow the air to pass through it in very small quantities. When a graduated movement is desired on the regulating valve for use in air currents, the same thermostat with slight modifications is used. In this case a single pipe only leads to the thermostat. When the tube A expands from the heat in the room, the pressure from the rod K is reduced and the port G is closed. The air is now confined in the single pipe, the pressure rises and the regulating valve is moved in such a position as to cut off a part or all of the warm air and admit tempered air. When the temperature in the room falls, because of the admission of this cooler air, the tube A contracts, and the port O is opened permitting the air to escape and operate the damper in the reverse direction. The amount of air admitted to the thermostat is controlled by a needle valve, hence its sensitiveness can be controlled. CHAPTER XV. ELECTRICAL, HEATING. In the present state of the heating business it seems almost unnecessary to discuss electrical heating, in any serious way, in connection with steam power plants. The reasons will be seen in the following brief discussion. Electrical heating can appeal to the public only from the standpoint of convenience, since a comparison of economies between steam, hot water or warm air heating on one hand, and electrical heating on the other, is wholly against the latter. Its application to the processes of heating will find its greatest economy in connection with water power plant where the combustion of fuel is eliminated from the prop- osition. This discussion will not bear in any way upon the water power generator. ISO. Equations Employed in Electrical Heating Design: 1 H. P. 746 watts. 1 H. P. = 33000 ft. Ibs. per min. 1980000 ft. Ibs. per hr. 1 B. t. u. = 778 ft. Ibs. 1 H. P. hr. = 1980000 -r- 778 = 2545 B. t. u. per hr. 1 H. P. hr. = 746 watt hrs. = 2545 B. t. u. per hr. 1 watt hr. = 3.412 B. t. u. per hr. 1 watt hr. 3.412 -f- 170 .02 sq. ft. of hot water rad. 1 watt hr. = 3.412 -^ 255 = .0134 sq. ft. of steam rad. 1 kilo-watt hr. = 20.1 sq. ft. of hot water rad. (108) 1 kilo-watt hr. = 13.4 sq. ft. of steam rad. (109) 181. Comparison between Electrical Heating and Hot Water and Steam Heating: The loss in transmitting electric- ity from the generators through the switchboard to the radi- ators may be small or large, depending upon the conditions of wiring, the current transmitted and the pressure on the line. In all probability it would equal or exceed the trans- mission losses in hot water or steam lines. Assuming these losses to be the same, then a fair comparison may be made in the cost of heating by the various methods. The operating efficiency of an electric heater is 100 per cent., since all the current that is passed into the heater is dissipated in the form of heat and no other losses are experienced. This is 254 HEATING AND VENTILATION not true of steam systems where the water of condensation is thrown away at fairly high temperatures. Where elec- tricity or steam is generated and distributed all in the same building, there is no line loss to be accounted for, since all of this heat goes to heating the building and counts as additional radiation. Equations 108 and 109 show the theoretical relation existing between electrical heating and hot water and steam heating compared at the power plant. The following dis- cussion is based, therefore, upon the assumption that 1 kilo-watt hour, in an electric radiator, will give off the same amount of heat as 20.1 and 13.4 square feet of hot water and steam radiation respectively. With coal having 13000 B. t. u. per pound and a furnace efficiency of 60 per cent., it will require 3412 -7- 7800 = .44 pounds of coal per hour. If coal co,sts $2.00 per ton of 2000 pounds, there will be an actual fuel expense of .044 cent. On the other hand, assuming the combined mechanical efficiency of an engine or turbo-gener- ator set to be 90 per cent., the heat from the steam that is turned into electrical energy per hour is 1000 ~ .90 = 1111 watts, for each kilo-watt delivered. Now, if this unit has 15 per cent thermal efficiency, we have the initial heat in the steam equivalent to 1111 -r- .15 = 7400 watt hours. From this obtain 7400 X 3.412 = 25249 B. t. u. per hour; or, 25249 -^ 7800 = 3.2 pounds of coal per hour. This, at the same rate as .shown above, would be worth .32 cent. Comparing, the electrical generation actually costs 7.2 times as much as the other. This comparison has dealt with the fuel costs at the plant and has not taken into account the depreciation, labor costs, etc., the object being to show relative efficiencies only. Another way of looking at this subject is as follows. A fairly large turbo-generator set (say 500 K. W.) will deliver 1 kilo-watt hour to the switchboard on 20 pounds of steam. With 10 per cent, additional steam for auxiliary units, this amounts to 22 pounds of steam per kilo-watt hour at the switchboard. One pound of steam generated in a plant of this kind with the above efficiencies and value of coal, also with a ,steam pressure of 150 pounds and a good feed water heater, will give to each pound of steam approximately 1000 B. t. u. This makes 22000 B. t. u. or 2.8 pounds of coal required to each kilo-watt output. This is about 10 per cent, less than the above figures. ELECTRICAL HEATING 255 The ratio of 7 to 1, as shown in the above efficiencies, does not seem to hold good in the selling price to the con- sumer. In round numbers, district steam and hot water heat- ing systems supply 25000 B. t. u. to the consumer for one cent. The cost for electrical energy to the consumer is be- tween 6 and 7 cents per kilo-watt. This gives 3412 -r- 6.5 525 B. t. u. for one cent. Comparing with the above, gives a ratio of 48 to 1. 182. The Probable Future of Electrical Heating: Be- cause of the low efficiency of electrical heating as compared to other methods of heating, it is very probable that it will not replace the other methods except in so far as the con- veniences of the user is the principal thing sought for, and the expense of operating a minor consideration. In some forms of domestic service, however, electrical heating is sure to find considerable usefulness. The temperatures of low pressure steam and hot water* together with the incon- venience of use, are such as to eliminate them from many of the household economies. They will probably continue to be used for house heating, water heating and laundry work. Occupations, however, that require temperatures above 250 degrees, such as broiling, frying, ironing, etc., the electrical supply will be in demand. REFERENCES. References on Electrical Heating. TECHNICAL PERIODICALS. The Heating and Ventilating Magazine. Electrical Heating, 5 eb. 1907, p. 28. Electric Heating, W. S. Hadaway, Jr., Nov. 1908, p. 28; Dec. 1908, p. 26. The Electrical World, Vol. 52, pages 450, 903, 1112 and 1358, and Vol. 53, pages 5, 274 and 921. CHAPTER XVI. SUGGESTIONS FOR A COURSE OF INSTRUCTION. 183. Preparation for the Course: In adapting this sub- ject to a college course, it should, if possible, be taken up during the last year of college work, when the ^student can have the benefit of a large part of the training in Heat, Thermodynamics, Engineering Design, and Steam Engines and Boilers, all of which subjects are of great value in heating and ventilating work. The subjects of Heat and Thermodynamics prepare for analytical and experimental investigation in heat transference, while a knowledge of engines, boilers and general machinery gives information of a more practical turn, the application of which is neces- sary in heating design. A course of study, as outlined here, is primarily theoretical but it should not stop there. To be of service in fitting a man for active participation in the work after leaving school, it must emphasize such points as relate to the layout of the drawings and to the mate- rials used in the construction as well. A course fitted to practical needs should not only require a full set of cal- culations for each design, but it should require a complete layout of each system. 184. Administration of the Work: The course should be administered, part in the class room, as lectures and reci- tations, and part (a set of designs) should be left to the student to work up largely upon his own responsibility and submit the same for approval. The work in the class room should be at least two hours per week, and may be divided between lectures and recitations in whatever manner is thought best. In the lec- tures, references should be made to the various authorities on heating and ventilating with suggestions that these authorities be looked up. The lectures should also include very full details concerning the laying out of such work, with suggestions concerning the proper selection of ma- terials. The recitations should be made as practical as possible to serve in bringing out the points that would probably be confusing in developing the designs. All class OUTLINE OB A COURSE 257 room work should be timed to suit the design under con- sideration, otherwise the design work and the class room work will be independent rather than mutually helpful. 185. Outline of the Work of Design: After two or three weeks devoted to the subjects of ventilation, radiating sur- faces, etc., the work of design should be taken up and might very properly cover the following systems of heat- ing: 1. Furnace heating, as applied to residences. Time al- lowed, three weeks. 2. Hot water heating, as applied to residences. Time allowed, three weeks. 3. Steam heating, as applied to residences. Time al- lowed, two weeks. 4. Plenum system of warm air heating, as applied to schools and low office buildings. Time allowed, four weeks. 5. District heating from a Central Station. Time al- lowed, four weeks. The above will be found to cover the work very thor- oughly and should be administered in such a way as to remove as much of the purely routine work as ppssible, otherwise the course which is planned for one-half year's work would be too long for the time allowed to the aver- age student by the school curriculum. As an illustration, the student prepared for this work is fairly well qualified to make mechanical drawings, and any relief which can be given from drawing work will permit the equivalent time being put to other and more important parts of the design. This relief can take the form of prepared building plans stamped off on standard sized paper, thus permitting the insertion of heating drawings on the same pages without the routine labor of reproducing an entirely new set of drawings. These plans may be made the same size as the blanks upon which the calculations are submitted, say, 8% x 11 inches and should always be different from any pre- viously given. The final report will then include every thing under one cover and can be filed away without dif- ficulty. For sample set of building plans, see Figs. 13, 14 and 15, with the furnace, pipes and registers removed. 186. Specifications: It is desirable that each man have experience in writing specifications for his own plans. This is 258 HEATING AND VENTILATION difficult for a beginner and requires considerable time to d 2102-5.000 3048625.000 12.0416 5.2536 455.53 16513.00 150 22500.000 3375000.000 12.2474 5.3133 471.24 17671.46 155 24025.000 3723875.000 12.4499 5.3717 486.95 18869.19 160 25600.000 4096000.000 12.6491 5.4288 502.65 20106.19 165 27225.000 4493125.000 12.8452 5.4848 518.36 21382.46 170 28900.000 4913000.000 13.0384 5.5397 534.07 22698.01 175 30625.000 359375.000 13.2288 5.5934 549.78 24052.82 180 32400.000 5832000.000 13.4164 5.6462 565.49 25446.90 185 3-1225.000 6331625.000 13.6015 5.6980 581.19 26880.25 190 36100.000 6859000.000 13.7840 5.7489 596.90 28352.87 195 38025.000 7414875.000 13.9642 5.7989 612.61 29864.77 200 40000.000 8000000.000 14.1421 5.8480 628.32 31415.93 205 42025.000 8615125.000 14.3178 5.8964 644.03 33006.36 210 44100.000 9261000.000 14.4914 5.9439 659.73 34636.06 215 46225.000 9938375.000 14.6629 5.9907 675.44 36305.03 230 48400.000 10648000.000 14.8324 6.0368 691.15 38013.27 225 50625.000 11390625.000 15.0000 6.0822 706.86 39760.78 230 52900.000 12167000.000 15.1658 6.1269 722.57 41547.56 235 55225.000 12977875.000 15.3297 6.1710 738.27 43373.61 240 57600.000 13824000.000 15.4919 6.2145 753.98 45238.93 245 60025.000 14706125.000 15.6525 6.2573 769.69 47143.52 350 62500.000 15625000.000 15.8114 6.2996 785.40 49087.39 255 65025.000 16581375.000 15.9687 6.3413 801.11 51070.52 260 67600.000 17576000.000 16.1245 6.3825 816.81 53092.92 265 70225.000 18609625.000 16.2788 6.4232 832.52 55154.59 270 72900.000 19683000.000 16.4317 6.4633 848.23 67255.63 276 No, Diam. Square Cube Sq. Boot Cube Root Circle Oircumf Area 275 75625.000 20796875.000 16.5831 6.5030 863.94 59395.74 280 78400.000 21952000.000 16.7332 6.5421 879.65 01575.28 285 81225.000 23149125.000 16.8819 6.5808 895.35 63793.97 290 84100.000 24389000.000 17.0294 6.6191 911.00 66051.99 295 87025.000 25672375.000 17.1756 0.6569 926.77 08349.28 800 90000.000 27000000.000 17.3205 6.6943 942.48 70085.83 305 93025.000 28372625.000 17.4642 6.7313 958.19 73061.66 310 96100.000 29791000.000 17.6068 6.7679 973.89 75476.76 315 99225.000 31255875.000 17.74821 6.8041 989.60 77931.13 320 102400.000 32768000.000 17.8885 6.8399 1005.31 80424.77 325 105625.000 34328125.000 18.0278 6.8753 1021.021 82957.68 330 108900.000 35937000.000 18.1659 6.9104 1036.73 85529.86 335 112225.000 37595375.000 18.3030 6.9451 1052.43 88141.31 340 115600.000 39304000.000 18.4391 6.9795 1068.14 90792.03 345 119025.000 41063625.000 18.5742 7.0130 1083.85 93482.00 350 122500.000 42875000.000 18.7063 7.0473 1099.50 96211.28 355 126025.000 44738875.000 18.8414 7.0807 1115.27 98979.80 360 129600.000 46656000.000 18.9737 7.1138 1130.97 101787.60 365 133225.000 48627125.000 19.1050 7.1460 1140.68 104034.67 370 136900.000 50653000.000 19.2354 7.1791 1162.39 107521.01 375 140625.000 52734375.000 19.3649 7.2112 1178.10 110440.62 380 144400.000 54872000.000 19.4936 7.2432 1193.81 113411.49 385 148225.000 57066625.000 19.6214 7.2748 1209.51 116415.64 390 152100.000 59319000.000 19.7484 7.3061 1225.22 119459.06 395 156025.000 61629875.000 19.8746 7.3372 1240.93 122541.75 400 160000.000 64000000.000 20.0000 7.3681 1256.64 125663.71 405 164025.000 66430125.000 20.1246 7.3980 1272.35 123824.93 410 168100.000 68921000.000 20.2485 7.4290 1288.05 132025.43 415 172225.000 71473375.000 20.3715 7.4590 1303.76 135205.20 420 176400.000 74088000.000 20.4939 7.4889 1319.47 138544.24 425 180625.000 76765625.000 20.6155 7.5185 1335.18 141802.54 430 184900.000 79507000.000 20.7364 7.5478 1350.88 145220.12 435 189225.000 82312875.000 20.8567 7.5770 1306.59 148616.97 440 193600.000 85184000.000 20.9762 7.6059 1382.30 152053.08 445 198025.000 88121125.000 21.0950 7.6346 1398.01 155528.47 450 202500.000 91125000.000 21.2132 7.6631 1413.72 159043.13 455 207025.000 94196375.000 21.3307 7.6914 1429.42 162597.05 460 211600.000 97336000.000 21.4476 7.7194 1445.13 106190.25 465 216225.000 100544625.000 21.5639 7.7473 1400.84 169822.72 470 220900.000 103823000.000 21.6795 7.7750 1476.55 173494.45 475 225625.000 107171875.000 21.7945 7.o025 1492.20 177205.46 480 230400.000 110592000.000 21.9089 7.8297 1507.90 180955.74 485 235225.000 114084125.000 22.0227 7.8508 1523.67 184745.28 490 240100.000 117649000.000 22.1359 7.8837 1539.38 183574.10 495 245025.000 121287375.000 22.2486 7.9105 1555.09 192442.18 500 250000.000 125000000.000 22.3607 7.9370 1570.80 196349.54 277 TABLE 2. Properties of Saturated Steam.* Absolute press 're Ibs. per sq. in. Tempera- ture Degrees F. Heat of the Liquid Heat of the Vaporiza- tion Total Heat Above 32 1 101.84 69.8 1034.7 1104.5 3 126.15 94.2 1021.9 1116.1 3 141.52 109.6 1012.2 1121.8 4 153.00 121.0 1005.5 1126.5 5 162.26 130.3 1000.0 1130.3 G 170.07 138.1 995.5 1133.6 7 176.84 144.9 991.4 - 1136.3 8 182.86 150.9 987.8 1138.7 9 188.27 156.4 984.5 1140.9 10 193.21 161.3 981.4 1142.7 11 197.74 165.9 978.6 1144.6 12 201.95 170.1 976.0 1146.1 13 205.87 174.1 973.6 1147.7 14 209.55 177.8 971.2 1149.0 14.7 212.00 180.3 969.7 1150.0 15 213.03 181.3 969.1 1150.4 16 216.31 184.6 967.0 1151.6 17 219.43 187.8 965.0 1152.8 18 222.40 190.8 963.1 1153.9 19 225.24 193.7 981.2 1154.9 20 227.95 196.4 059.4 1155.8 21 230.56 199.1 957.7 1156.8 22 233.07 201.6 956.0 1157.6 23 235.50 204.1 954.4 1158.5 84 237.82 206.4 952.9 1159.3 25 240.07 208.7 951.4 1160.1 26 242.26 210.9 949.9 1160.8 27 244.36 213.0 948.5 1161.5 28 246.41 215.1 947.1 1162.2 29 248.41 217.2 945.8 1163.0 60 250.34 219.1 944.4 1163.5 81 252.22 221.0 943.1 1164.1 82 254.05 222.9 941.8 1164.7 S3 255.84 224.7 940.6 1165.3 84 257.59 226.5 939.4 1165.9 35 259.29 228.2 938.3 1166.4 86 260.96 229.9 937.1 1167.0 87 262. 5K 231.6' 935.9 1167.5 38 264.17 233.2 934.8 1168.0 89 265.73 234.8 933.7 1168.6 40 267.20 236.4 932.6 1169.0 41 268.76 237.9 931.6 1169.6 42 270.23 239.4 930.6 1170.0 43 271.66 240.8 929.5 1170.3 44 273.07 242.3 928.5 1170.8 'Condensed from Peabody's Steam Tables. 278 Absolute press're Ibs. per sq. in. Tempera- ture Degrees F. Heat of the Liquid Heat of the Vaporiza- tion Total Heat Above 32 45 274.46 243.7 927.5 1171.2 46 275.83 245.1 926.6 1171.7 47 277.16 246.4 925.6 1172.0 48 278.47 247.8 924.7 1172.5 49 279.76 249.1 923.8 1172.9 50 281.03 250.4 922.8 1173.2 51 282.28 251.7 921.9 1173.6 52 283.52 253.0 921.0 1174.0 53 284.74 254.2 920.1 1174.3 54 285.93 255.4 919.3 1174.7 55 287.09 256.6 918.4 1175.0 66 288.25 257.8 917.6 1175.4 57 289.40 259.0 916.7 1175.7 58 290.53 260.1 915.9 1176.0 59 291.64 261.3 915.1 1176.4 60 292.74 262.4 914.3 1176.7 61 293.82 263.5 913.5 1177.0 62 294.88 264.6 912.7 1177.3 63 295.93 265.7 911.9 1177.6 64 296.97 266.7 911.1 1177.8 65 298.00 267.8 910.4 1178.3 66 299.02 268.8 909.6 1178.4 67 300.02 269.8 908.9 1178.7 68 301.01 270.9 908.1 1179.0 69 301.99 271.9 907.4 1179.3 70 302.96 272.9 906.6 1179.5 71 S03.91 273.8 905.9 1179.7 72 304.86 274.8 905.3 1180.0 73 305.79 275.8 904.5 1180.3 74 306.72 270.7 903.8 1180.5 75 307.64 277.7 903.1 1180.8 76 308.54 278.6 902.4 1181.0 77 309.44 279.5 901.8 1181.3 78 310.33 280.4 901.1 1181.5 79 311.21 281.3 900.4 1181.7 80 312.08 282.2 899.8 1182.0 81 312.94 283.1 899.1 1182.2 82 313.79 283.9 898.5 1182.4 83 314.63 284.8 897.8 1182.6 84 315.47 285.7 897.2 1182.9 85 316.30 286.5 896.6 1183.1 86 317.12 287.4 895.9 1183.3 87 317.93 288.2 895.3 1183.5 88 318.73 289.0 894.7 1183.7 89 319.53 289.9 894.1 1184.0 90 320.32 290.7 893.5 1184.2 91 321.10 291.5 892.9 1184.4 92 321.88 292.3 892.3 1184.6 93 322.65 293.1 891.7 1184.8 94 323.41 293.9 891.1 1185.0 279 Absolute press 're Ibs. per sq. in. Tempera- ture Degrees P. Heat of the Liquid Heat of the Vaporiza- tion Total Heat Above 32 95 324.16 294.6 890.5 1185.1 96 324.91 295.4 889.9 1185.3 97 325.66 296.2 889.3 1185.5 98 326.40 296.9 888.7 1185.6 99 327.13 297.7 888.2 1185.9 100 327.86 298.5 887.6 1186.1 101 328.58 299.2 887.0 1186.2 102 329.30 299.9 886.5 1186.4 103 330.01 300.6 885.9 1186.5 104 330.72 301.4 885.3 1186.7 105 331.42 302.1 884.8 1186.9 106 332.11 302.8 884.3 1187.1 107 332.79 303.5 883.7 1187.2 108 333.48 304.2 883.2 1187.4 109 334.16 304.9 882.6 1187.5 110 334.83 305.6 882.1 1187.7 111 335.50 306.3 881.6 1187.9 112 336.17 307.0 881.0 1188.0 113 336.83 307.7 880.5 1188.2 114 337.48 308.3 880.0 1188.3 115 338.14 309.0 879.5 1188.5 116 338.78 309.7 879.0 1188.7 117 339.42 310.3 878.5 1188.8 118 340.06 311.0 878.0 1189.0 119 340.69 311.7 877.4 1189.1 120 341.31 312.3 876.9 1189.2 121 341.94 312.9 876.4 1189.3 123 342.56 313.6 875.9 1189.5 123 343.18 314.2 875.4 1189.6 124 343.79 314.8 875.0 1189.8 125 344.39 315.5 874.5 1190.0 126 345.00 316.1 874.0 1190.1 127 345.60 316.7 873.5 1190.2 128 346.20 317.3 873.0 1190.3 129 346.79 317.9 872.6 1190.5 130 347.38 318.6 872.1 1190.7 131 347.96 319.2 871.6 1190.8 132 348.55 319.8 871.1 1190.9 133 349.13 320.4 870.7 1191.1 134 349.70 320.9 870.2 1191.1 135 350.27 321.5 869.8 1191.3 136 350.84 322.1 869.3 1191.4 137 351.41 322.7 868.8 1191.6 138 351.98 323.3 868.3 1191.6 139 352.54 323.9 867.9 1191.8 140 353.09 324.4 867.4 1191.8 141 353.65 325.0 867.0 1192.0 142 354.20 325.6 866.5 1192.1 143 354.75 326.2 866.1 1192.3 144 355.29 326.7 865.6 1192.3 280 Absolute press 're Ibs. per sq. in. Tempera- ture Degrees F. Heat of the Liquid Heat of the Vaporiza- tion Total Heat Above 32 1 145 355.83 327.3 865.2 1193.5 140 356.37 337.8 864.8 1192.6 147 356.91 328.4 864.3 1192.7 148 357.44 328.9 863.9 1192.8 149 357.97 329.5 863.5 1193.0 150 358.50 330.0 863.0 1193.0 151 359.03 330.6 863.6 1193.2 153 359.54 331.1 862.2 1193.3 153 360.06 331.6 861.8 1193.4 154 360.57 332.2 861.3 1193.5 155 361.09 332.7 860.9 1193.6 156 361.60 333.2 860.5 1193.7 157 363.11 333.8 860.1 1193.9 158 363.62 334.3 859.6 1193.9 159 363.13 334.8 859.3 1194.0 160 363.63 335.3 858.8 1194.1 161 364.12 335.9 858.4 1194.3 162 364.62 336.4 858.0 1194.4 163 365.11 336.9 857.6 1194.5 164 365.60 337.4 857.2 1194.6 165 366.09 337.9 856.8 1194.7 166 366.58 338.4 856.4 1194.8 167 367.06 338.9 856.0 1194.9 168 367.54 339.4 855.6 1195.0 169 368.03 339.9 855.3 1195.1 170 368.50 340.4 854.8 1196.2 171 368.97 340.9 854.4 1195.3 173 369.45 341.4 854.0 1195.4 173 369.93 341.8 853.6 1195.4 174 370.39 342.3 853.3 1195.5 175 370.86 342.8 852.8 1195.6 176 371.33 343.3 852.4 1195.7 177 371.78 343.8 853.0 1195.8 178 373.24 344.2 851.6 1195.8 179 373.70 344.7 851.3 1196.0 180 373.16 345.2 850.9 1196.1 181 373.61 345.7 850.5 1196.2 183 374.07 346.2 850.1 1196.3 183 374.53 346.6 849.7 1196.3 184 374.98 347.1 849.4 1196.5 185 375.41 347.5 849.0 1196.5 186 375.86 348.0 848.6 1196.6 187 376.30 348.5 848.3 1196.7 188 376.74 348.9 847.8 1198.7 189 377.18 349.4 847.5 1196.9 190 377.61 349.8 847.1 1196.9 191 378.05 350.3 846.8 1197.1 192 378.49 350.7 846.4 1197.1 193 378.92 351.3 846.0 1197.2 194 379.35 351.6 845.7 1197.3 281 Absolute press're Ibs. per sq. in. Tempera- ture Degrees F. Heat of the Liquid Heat of the Vaporiza- tion Total Heat Above 32 195 379.78 352.1 845.3 1197.4 196 380.20 352.5 844.9 1197.4 197 380.63 353.0 844.6 1197.6 198 381.05 353.4 844.2 1197.6 19 381.47 353.8 843.9 1197.7 200 381.89 354.3 843.5 1197.8 201 382.31 354. '< 843.1 1197.8 202 S82.73 355.1 842.8 1197.9 203 383.15 355.6 842.4 1198.0 204 383.56 356.0 842.1 1198.1 5-05 383.98 356.4 841.7 1198.1 06 384.39 356.9 841.3 1198.2 2O7 384.80 357.3 841.0 1198.3 208 385.21 357.7 840.7 1198.4 209 385.61 358.1 840.3 1198.4 310 386.02 358.6 840.0 1198.6 211 386.42 359.0 839.6 1198.6 212 386.82 359.4 839.3 1198.7 213 387.22 359.8 839.0 1198.8 214 387.62 360.2 838.6 1198.8 215 388.02 360.6 838.3 1198.9 216 388.41 361.0 837.9 1198.9 217 388.80 361.4 837.6 1199.0 218 389.20 361.9 837.2 1199.1 219 389.59 362.3 836.9 1199.2 230 389.98 362.7 836.6 1199.3 221 390.37 363.1 836.2 1199.3 222 390.76 363.5 835.9 1199.4 223 391.14 363.9 835.6 1199.5 224 391.53 364.3 835.2 1199.5 225 391.91 364.7 834.9 1199.8 226 392.29 365.1 834.6 1199.7 227 392.67 365.5 834.3 1199.8 228 393.04 365.9 833.9 1199.8 229 393.42 366.2 833.6 1199.8 230 393.80 366.6 833.3 1199.9 231 394.18 367.0 832.9 1199.9 232 394.56 367.4 832.6 1200.0 233 394.93 367.8 832.3 1200.1 234 395.30 368.2 832.0 1200.2 235 395.67 368.6 831.7 1200.3 236 396.04 369.0 831.3 1200.3 237 396.41 369.4 831.0 1200.4 238 c96.78 369.7 830.7 1200.4 239 397.14 370.1 830.4 1200.5 240 397.50 370.5 830.1 1200.6 241 397.86 370.9 829.8 1200.7 242 398.22 371.2 829.5 1200.7 243 398.59 371.6 829.1 1200.7 244 398.96 372.0 828.8 1200.8 282 Absolute press're Ibs. per sq. in. Tempera- ture Degrees F. Heat of the Liquid Heat of the Vaporiza- tion Total Heat Above 32 245 399.32 372.4 828.5 1200.9 246 399.68 372.8 828.2 1201.0 247 400.04 373.2 827.8 1201.0 248 400.39 373.5 827.5 1201.0 249 400.75 373.9 827.2 1201.1 250 401.10 374.2 826.9 1201.1 251 401.45 374.6 826.6 1201.2 262 401.79 375.0 826.3 1201.3 253 402.14 375.3 826.0 1201.3 254 402.48 375.7 825.7 1201.4 255 402.83 376.0 825.4 1201.4 256 403.17 376.4 825.1 1201.6 257 403.52 376.8 824.8 1201.6 258 403.86 377.1 824.5 1201.6 259 404.21 377.5 824.2 1201.7 260 404.55 377.8 823.9 1201.7 261 404.89 378.2 823.6 1201.8 262 405.23 378.5 823.3 1201.8 263 405.57 378.9 823.0 1201.9 264 405.90 379.2 822.7 1201.9 265 406.23 379.6 822.4 1202.0 268 406.57 379.9 822.1 1202.0 267 406.90 380.3 821.8 1202.1 268 407.23 380.6 821.5 1202.1 . 269 407.57 381.0 821.2 1202.2 270 407.90 381.3 820.9 1202.2 271 408.23 381.7 820.6 1202.3 272 408.57 382.0 820.3 1202.3 273 408.90 382.4 820.1 1202.5 274 409.23 382.7 819.8 1202.5 275 409.57 383.1 819.5 1202.6 276 409.90 383.4 819.2 1202.6 277 410.23 383.8 818.9 1202.7 278 410.55 384.1 818.6 1202.7 279 410.87 384.4 818.3 1202.7 280 411.19 384.8 818.0 1202.8 281 411.52 385.1 817.7 1202.8 411.84 385.4 817.4 1202.8 283 412.16 385.8 817.2 1203.0 284 412.47 386.1 816.9 1203.0 285 412.78 386.4 816.6 1203.0 286 413.09 386.7 816.3 1203.0 287 413.41 387.1 8i6.0 1203.1 288 413.72 387.4 815.8 1203.2 289 414.03 387.7 815.5 1203.2 290 414.35 388.1 815.2 1203.3 291 414.68 388.4 814.9 1203.3 293 415.00 388.7 814.0 1203.3 293 415.31 389.1 814.3 1203.4- 294 415.63 389.4 814.1 1203.5 283 Absolute Pressure Pounds Per Square Inch Temperature Degrees Fahrenheit Heat of the Liquid Heat of the Vaporization Total Heat Above 32 295 415.95 389.7 813.8 1203.5 293 416.24 390.0 813.5 1203.5 297 416.55 390.4 813.2 1203.6 298 416.85 390.7 813.0 1203.7 299 417.15 391.0 812.7 1203.7 300 417.45 391.3 812.4 1203.7 301 417.76 391.6 812.1 1203.7 303 418.06 391.9 811.9 1203.8 303 418.36 392.3 811.6 1203.9 804 418.67 392.6 811.3 1203.9 SOS 418.97 392.9 811.1 1204.0 306 419.26 393.2 810.8 1204.0 807 419.56 393.5 810.5 1204.0 808 419.85 393.8 810.3 1204.1 309 420.15 394.1 810.0 1204.1 310 420.45 394.4 809.7 1204.1 311 420.76 394.8 809.5 1204.3 812 421.06 395.1 809.2 1204.3 313 421.35 395.4 808.9 1204.3 314 421.65 395.7 808.7 JEZ04.4 315 421.94 396.0 808.4 1204.4 316 422.24 396.3 808.1 1204.4 317 422.53 396.6 807.9 1204.5 318 422.82 396.9 807.6 1204.5 319 423.11 397.2 807.3 1204.5 320 423.40 397.5 807.1 1204.6 321 423.69 397.8 806.8 1204.6 322 423.97 398.1 806.6 1204.7 823 424.26 398.4 806.3 1204.7 824 424.54 398.7 806.0 1204.7 325 424.83 399.0 805.8 1204.8 326 425.11 399.3 805.5 1204.8 327 425.40 399.6 805.3 1204.9 328 425.69 399.9 805.0 1204.9 329 425.97 400.2 804.7 1204.9 330 426.26 400.5 804.5 1205.0 311 426.54 400.8 804.2 1205.0 ' 332 426.83 401.1 804.0 1205.1 333 427.11 401.4 808.7 1205.1 334 427.39 401.7 803.5 1205.2 335 427.67 402.0 803.2 1205.2 836 427.94 402.2 803.0 1205.2 284 TABLE 3. Naperian Logarithms. 2.7182818 Log e = 0.4342945 = M. .0 0.0000 4.1 .4110 7.2 1.9741 .1 0.0953 4.2 .4351 7.3 1.9879 .2 0.1823 4.3 .4586 7.4 2.0015 .3 0.2624 .4 .4816 7.5 2.0149 .4 0.3365 .6 .5041 7.6 2.0281 .5 0.4055 .6 1.5261 7.7 2.0412 .6 0.4700 .7 1.5476 7.8 2.0541 .7 0.5306 .8 1.5686 7.9 2.0668 .8 0.5878 4.9 1.5892 8.0 2.0794 .9 0.6418 6.0 1.6094 8.1 2.0919 2.0 0.6931 6.1 1.6292 8.3 2.1041 2.1 0.7419 5.2 1.6487 8.3 2.1163 2.2 0.7884 5.3 1.6677 8.4 2.1283 2.3 0.8329 5.4 1.6864 8.5 2.1401 2.4 0.8755 5.5 .7047 8.6 2.1518 2.5 0.9163 6.6 .7228 8.7 2.1633 2.6 0.9555 5.7 .7405 8.8 2.1748 2.7 0.9933 5.8 .7579 8.9 2.1861 2.8 .0296 5.9 .7750 9.0 2.1972 2.9 .0647 6.0 .7918 9.1 2.2083 3.0 .0986 6.1 .8083 9.2 2.2192 3.1 .1314 6.2 .8245 9.3 2.2300 3.3 .1632 6.3 .8405 9.4 2.2407 3.3 .1939 6.4 .8563 9.5 2.2513 3.4 .2238 6.5 .8718 9.6 2.2618 3.5 .2528 6.6 .8871 9.7 2.2721 3.6 .2809 6.7 .9021 9.8 2.2824 3.7 .3083 6.8 1.9169 9.9 2.2925 3.8 .3350 6.9 1.9315 10.0 2.3026 3.9 1.3610 7.0 1.9459 4.0 1.3863 7.1 1.9601 TABLE 4. Water Conversion Factors.* TJ. S. gallons U. S. gallons U. S. gallons U. S. gallons Cubic inches of water (39.1) Cubic inches of water (39.1) Cubic inches of water (39.1) Cubic feet of water (89.1) Cubic feet of water (39.1) Cubic feet of water (39.1) Pounds of water Pounds of water Pounds of water X X X X X X X X X X X X X 8.33 0.13368 231.00000 3.78 0.036024 0.004329 0.576384 62.425 7.48 0.028 27.72 0.01602 0.12 pounds, cubic feet, cubic inches, liters, pounds. U. S. gallons, ounces, pounds. U. S. gallons, tons, cubic inches, cubic feet. U. S. gallons. * American Machinist Hand Book. 285 TABLE 5. Volume and Weight of Wry Air at Different Temperatures.* Under a constant atmospheric pressure of 29.92 inches of mercury, the volume at 32 F. being 1. Tempera- ture Volume. Weight of a Cubic Tempera- ture Weight of Volume. a Cubic Fahr. Foot. Fahr. Foot. .935 .0864 500 1.954 .0413 12 .960 .0842 552 2.056 .0385 221 .980 .0824 600 2.150 .0376 32 1.000 .0807 650 2.260 .0357 42 1.020 .0791 700 2.362 .0338 52 1.041 .0776 750 2.465 .0328 62 1.061 .0761 800 2.566 .0315 72 1.082 .0747 850 2.668 .0303 82 1.102 .0733 900 2.770 .0292 92 1.122 .0720 950 2.871 .0281 102 1.143 .0707 1000 2.974 .0268 112 1.163 .0694 1100 3.177 .0264 122 1.184 .0682 1200 3.381 .0239 132 1.204 .0671 1300 3.584 .0225 142 1.224 .0659 1400 3.788 .0313 152 1.245 .0649 1500 3.993 .0202 162 1.265 .0638 1600 4.196 .0192 172 1.285 .0628 1700 4.402 .0183 182 1.306 .0618 1800 4.605 .0175 192 1.326 .0609 1900 4.808 .0168 202 1.347 .0600 2000 5.012 .0161 212 1.367 .0591 2100 5.217 .0155 230 1.404 .0575 2200 5.420 .0149 250 1.444 .0559 2300 5.625 .0142 275 1.495 .0540 2400 5.827 .0138 300 1.546 .0522 2500 6.032 .0133 325 1.597 .0506 2600 6.236 .0130 350 1.648 .0490 2700 6.440 .0125 375 1.689 .0477 2800 6.644 .0121 400 1.750 .0461 2900 6.847 .0118 450 1.852 .0436 3000 7.051 .0114 *Suplee's M. E. Eeference Book. 286 TABLE 6. Weight of Pure Water per Cubic Foot at Various Temperature.* Temp. Degrees Fahr. Weight Lbs. per Cu. Ft. B. t. u. Per Pound above 33. Temp. Degrees Fahr. Weight Lbs. per Cu. Ft. B. t. u. Per Pound above 3$. 32 62.42 0.00 77 62.26 45.03 33 62.42 1.00 78 63.25 46.03 34 62.42 2.00 79 62.34 47.03 35 62.42 3.00 80 63.23 48.04 36 62.42 4.00 81 62.22 49.04 37 62.42 5.00 83 62.21 50.04 38 62.43 6.00 83 62.20 51.04 39 62.43 7.00 84 62.19 53.04 40 62.42 8.00 85 62.18 53.05 41 62.43 9.00 86 62.17 54.05 42 62.42 10.00 87 62.16 55.05 43 62.42 11.00 88 62.15 56.05 44 62.42 12.00 89 62.14 57.05 45 62.42 13.00 90 62.13 58.06 46 62.43 14.00 91 62.12 59.06 47 62.42 15.00 93 62.11 60.06 48 62.41 16.00 93 62.10 61.0(5 49 62.41 17.00 94 62.09 62.06 50 62.41 18.00 95 62.08 63.07 51 62.41 19.00 96 62.07 64.07 52 62.40 20.00 97 62.06 65.07 53 62.40 21.01 98 62.06 66.07 54 62.40 22.01 99 62.03 67.08 55 62.39 23.01 100 63.02 68.08 56 62.39 24.01 101 62.01 69.08 57 63.39 25.01 102 62.00 70.09 58 62.38 26.01 103 61.99 71.09 59 62.38 27.01 104 61.97 72.09 60 62.37 28.01 105 61.96 73.10 01 62.37 29.01 106 61.95 74.10 63 62.36 30.01 107 61.93 75.10 63 62.36 31.01 108 61.92 76.10 64 62.35 32.01 109 61.91 77.11 65 62.34 33.01 110 61.89 78.11 66 62.34 34.02 111 61.88 79.11 67 62.33 35.02 112 61.86 80.12 68 62.33 36.02 113 61.85 81.12 69 62.32 37.02 114 61.83 83.13 70 62.31 38.03 115 61.83 83.13 71 62.31 39.02 116 61.80 84.13 72 62.30 40.02 117 61.78 85.14 73 62.29 41.02 118 61.77 86.14 74 62.28 42.03 119 61.75 87.15 75 62.28 43.03 120 61.74 88.15 76 62.27 44.03 121 61.72 89.15 "Kent's M. E. Pocket-Book. 287 Temp. Degrees Fahr. Weight Lbs. per Cu. Ft. B. t. u. Temp. Per Pound Degrees above 32. Fahr. Weight Lbs. per Cu. Ft. B. t. u. Per Pound above 32. 122 61.70 90.16 167 60.83 135.43 123 61.68 91.16 168 60.81 136.44 124 61.67 92.17 169 60.79 137.45 125 61.65 93.17 170 60.77 138.45 120 61.63 94.17 171 a. 75 139.46 127 61.61 95.18 172 60.73 140.47 128 61.60 96.18 173 60.70 141.48 129 61.58 97.19 174 60.68 142.49 130 61.56 98.19 17 60.68 " 143.50 131 61.54 99.20 176 60.64 144.51 133 61.52 100.20 177 60.62 145.52 133 61.51 101.21 ITS 60.59 146.52 134 61.49 102.21 179 60.57 147.53 135 61.47 103.22 180 60.55 148.54 136 61.45 104.22 181 60.53 149.55 137 61.43 105.23 182 60.50 150.56 138 61.41 106.23 183 60.48 151.57 139 61.39 107.24 184 (50.46 152.58 140 61.37 108.25 185 60.44 153.59 141 61.36 109.25 186 60.41 154.60 142 61.34 110.26 187 60.39 155. 6 1 143 61.32 111.26 188 60.37 156.62 144 61.30 112.27 189 60.34 157.63 145 61.28 113.28 190 60.32 158.64 140 61.26 114.28 191 60.29 159.65 147 61.24 115.29 192 60.27 160.67 148 61.23 116.29 193 60.25 161.68 149 61.20 117.30 194 60.22 162.69 150 61.18 118.31 195 60.20 163.70 151 61.16 119.31 196 60.17 164.71 152 61.14 120.32 197 60.15 165.72 153 61.12 121.33 198 60.12 166.73 154 61.10 122.33 199 60.10 167.74 155 61.08 123.34 200 60.07 168.75 156 61.06 124.35 201 60.05 169.77 157 61.04 125.35 202 60.02 170.78 158 61.02 126.36 203 60.00 171.79 159 61.00 127.37 204 59.97 172.80 -160 60.98 128.37 205 59.95 173.81 161 60.96 129.38 206 59.92 174.83 162 60.94 130.39 207 59.89 175.84 163 60.92 131.40 206 59.87 176.85 164 60.90 132.41 209 59.84 177.86 165 60.87 133.41 210 59.82 178.87 166 60.85 134.42 211 59.79 179.89 212 59.76 180.90 288 TABLE 7. Boiling: Points of Water at Different Heights of Vacuui Temperature Fahr. Height of Mercury in Vacuum Tube in Inches. Temperature Fahr. Height of Mercury in Vacuum Tube in Inches. 212.0 0.00 175.8 16.00 210.3 1.00 172.6 17.00 208.5 2.00 169.0 18.00 206.8 3.00 165.3 19.00 204.8 4.00 161.2 20.00 202.9 5.00 156.7 21.00 200.9 6.00 151.9 22.00 199.0 7.00 146.5 23.00 196.7 8.00 140.3 24.00 194.5 9.00 133.3 25.00 192. 2 10.00 124.9 26.00 189.7 11.00 114.4 27.00 187.3 12.00 108.4 28.00 184.6 13.00 102.0 29.00 181.3 14.00 98.0 29.92 178.9 15.00 TABLE 8. Weight of Water With Air Per Cubic Foot at Different Temperatures and Saturation. fc fe . . . & _ -M m 4J ' m ** -P" .J -M .1 ** ft a! ft gjfl ft as ft a! ft a 3 ft al '53 g 7T *c3 a ' 3 S ' g a " '^ a '5 g o s H ^o & o H 1 ^0 | -20 0.166 2 0.529 1 24 1.483 40 3.539 68 7.480 90 14.790 19 0.174 3 0.554 35 1.551 47 3.667 69 7.726 91 15.234 18 0.184 4 0.582 26 1.623 48 3.800 70 7.980 93 15.C89 17 0.196 5 0.610 37 1.697 49 3.936 71 8.240 93 16.155 -16 0.207 6 0.639 28 1.773 50 4.076 72 8.508 94 16.634 15 0.218 7 0.671 29 1.853 51 4.222 73 8.782 95 17.134 14 0.231 8 0.704 30 1.935 53 4.372 74 9. 063 96 17.626 13 0.243 9 0.739 31 2.022 53 4.526 75 9.356 97 18.142 12 0.257 10 0.776 32 2.113 54 4.685 76 9.655 98 18.671 11 0.270 11 0.816 33 3.194 55 4.849 77 9.962 99 19.213 10 0.285 13 0.856 34 2.279 56 5.016 78 10.377 100 19.766 9 0.300 13 0.898 35 2.366 57 5.191 79 10.631 101 20.335 8 0.316 14 0.941 S6 2.457 58 5.370 80 10.934 103 20.^17 7 0.333 15 0.986 37 2.550 59 5.555 81 11.275 103 21. ,4 6 0.350 16 1.032 38 2.646 60 5.745 83 11.626 104 22.125 5 0.370 17 1.080 39 2.746 61 5.941 83 11.987 105 23.750 4 0.389 18 1.128 40 2.8-19 62 6.142 84 12.356 106 23.393 3 0.411 19 1.181 41 2.955 63 6.349 85 12.736 107 24.048 3 0.434 20 1.235 43 3.061 64 6.6C3 86 13.127 108 24.720 1 0.457 21 1.294 43 3.177 65 6.782 87 13.526 109 25.408 0.481 23 1.355 44 3.294 66 7.009 88 13.937 110 ?6.112 1 0.505 23 1.418 45 3.414 67 7.241 89 14.359 289 TABLE 9. Properties of Air With Moisture under Pressure of Atmosphere. * So X) Mixtures of air saturated 2 g Q) O >> .2^ with vapor. K a "flrH CLJ '" OS S & 1 S^m" Weight of cubic > o> ~? O.S O 1 ^.~ a foot of the ts c +J ^ O 60 ,0 S-i 0) '3 "^ &B p 'S 03 Cj^j gg 8| o.d n ^fl g| 3 fcflS ci t s-i ^ S| ^1 -D Oj 5^ O 0) w g -s- o ft fl 'Z'~ o O Q^ i( ^ 4J 4 *i-H 0^ 5 ft 0> 5 to O OJ-*- 1 C .2 Ss "3-2 O ofc -'s.S 2-S 0) H >$ Is ^ ft i'S 3 a II *. C3 Wfc Us P C 00 1 2 3 4 5 6 7 8 9 10 31 12 .935 nsfii 0.044 39.877 .0863 .000079 .086379 .00092 1092 40 48.5 12 .960 .0842 0.074 39.849 .0840 .000130 .084130 .00115 646 IQi 50.1 22 '.980 !o824 0.118 29! 803 .0821 .000202 1 082302 .00245 406.40 51.1 32 1.000 .0807 0.181 29.740 .0802 .000304 .080504 .00379 263.81 3289.0 52.0 42 1.020 .0791 0.367 29.654 .0784 .000440 .078840 .00561 178.18 2252.0 53.2 52 1.041 .0766 0.388 29.53? .0766 .000627 .077227 .00819 122.17 1595.0 54.0 80 1.057 .0764 0.522 29.399 0751 .000830 .075252 .01251 92.27 1227.0 55.0 62 1.061 .0761 0.556 29 365 .0747 .000881 .075581 .01179 84.79 1136.0 56.2 70 1.078 .0750 0.75-4:29.182 .0731 .001153 .073509 .01780 64.59 88?. f>7.3 72 1.083 .0747 .0.785 29.136 .0727 .001221 .073931 .01680 59.54 819.0 58.5 82 1.103 .0733 1.099 28.82C .0706 .001667 .072267 .02361 42.35 600-0 58.7 92 1.133 .0720 1.501 38.420 .0684 .002250 .070717 .03289 30.40 444.0 58.9 100 1.139 .0710 1.929 2r.99 .0664 .0028-18 .069261 .04495 23.66 356.0 59.1 103 1.143 .0707 2.036 27.885 .0653 .002997 .068897 .04547 2] .98 334.0 59.5 112 1.163 .0694 2.731 37.190 .0631 .003946 .067042 .06253 15.99 353.0 60.6 122 1.184 .0682 3.621 26.300 .0599 .005142 .065046 .08584 11.65 194.0 61.7 132 1.204 .0671 4.752 25.169 .0564 .OC6639 .063039 .11771 8.49 151.0 62.5 142 1.224 .0660 6.165 23.756 .0534 .008473 .060873 .16170 6.18 118.0 63.7 152 1.245 .0649 7.930 21.991 .0477 .010710 .058416 .22465 4.45 93.3 65.0 162 1.265 .0638 10.099 19.823 .0423 .013415 .055715 .31713 3.15 74.5 66.1 172 1.285 .0628 12.758 17.163 .0360 .016682 .052682 .46338 2.16 59.2 67.1 182 1.306 .0618115.960 13.961 .0288 .020536 .049336 .71300 1.402 48.6 68.0 192 1.326 .06Q9;19.828 10.093 .0205 .025142 .045642 1.22643 .815 39.8 68.9 202 1.347 .0600 24.450 5.471 .0109 .030545 .041445 2.80230 .357 82.7 70.2 212 1.367 .0591 29.931 0.000 .0000 .038820 .036320 finite .000 27.1 71.4 "Carpenter's H. & V. B. and Sturtevant's Mech. Draft. 290 (I) Q s i I i hi 21 S 155 niiiiiiiiiiiiiiiiiiiiii 291 TABLE 11. Fuel Value of American Coals.* COAL, Name or Locality. Fuel Value per Pound of Coal. B. t.u. calculated. B.'t.u. by calorimeter. Theoretical evap- oration in Ibs. from and at 212 F ARKANSAS. Spadra, Johnson Co 14,420 9,215 13,560 8,500 14,020 13,097 14,391 15,198 9,326 13,714 13,414 14,199 13,300 14,200 11,813 11,756 11,781 9,035 9,739 13,123 8,703 9,890 11,756 13,104 12,936 9,450 12,963 14,373 14.90 12.23 12.17 9.54 14.04 8.80 13.19 9.35 10.09 13.68 14.50 13.56 9.01 14.89 16.76 9.65 10.24 13.17 14.30 13.90 14.70 12.73 13.46 13.39 9.78 13.41 14.71 14.70 Coal Hill, Johnson Co. Huntington Co. Lignite _ COLORADO. Lignite Lignite slack ILLINOIS. Big Muddy, Jackson Co Colchester, Slack Giliespie, Macoupin Co. Mercer Co. INDIANA. Block Cannel . IOWA. Good cheer KENTUCKY. Caking _ __ Cannel Lignite MISSOURI. Bevier Mines NEW MEXICO. Coal OHIO. Briar Hill, Mahoning Co. Hocking Valley PENNSYLVANIA. Anthracite Anthracite, pea Pittsburgh (average) Youghiogheney TEXAS". Port Worth Lignite WEST VIRGINIA. Pocahontas New River _ __ _ *Sturtevant's "Mechanical Draft." 292 TABLE 12. Capacities of Chimneys,* Inside Diameter of Lined Flue (Inches) Maximum Sq. Ft. of Cast-iron Radiating Surface and B. t. u. for a Flue of the Given Diameter and Height. | W ,cj to i a be 5 i W ,a &o a i w 3 & 3 3 00 6 7 8 9 10 12 15 18 Steam 146 243 36500 228 379 57000 327 544 81750 445 742 111250 582 969 145500 909 1514 227250 1537 2561 334250 2327 3878 581750 175 291 43750 273 455 68250 392 653 98000 534 890 133500 698 1163 174500 1090 1817 272500 1844 3073 461000 2792 4653 698000 204 340 51000 319 531 79750 457 763 114250 623 1038 155750 814 1357 203500 1272 2120 318000 2151 3586 537750 3257 5429 814250 233 388 58250 364 607 91000 523 871 130750 712 1187 178000 930 1551 232500 1454 2423 363500 2458 4098 614500 3722 6204 930500 262 437 65500 410 683 102500 588 980 147000 801 1335 200250 1047 1745 261750 1636 2726 409000 2766 4610 691500 4188 6980 1047000 291 485 72750 455 758 113750 653 1088 163250 890 1483 222500 1163 1938 290750 1817 3028 454250 3073 5122 768250 4653 7755 1163250 Hot Water B. t. u. ___ Steam _. _ Hot Water B. t. u. _ _ _ Steam Hot Water . B. t. u. ___ _ Steam Hot Water B. t. u. Steam Hot Water B. t. u. Steam Hot Water B. t. u. Steam _-.___ Hot Water B. t. u. Steam _ Hot Water. __ B. t. u - Radiation is calculated at 250 B. t. u. steam, 150 B. t. u. water. *The Model Boiler Manual. 293 TABLE 13. Equalization of Smoke Flues Commercial Inside Diameter Lined Flue Brick Flue Not Lined Well Built Rectangular Lined Flue Outside of Tile Outside Iron Stack 6 7 8 9 10 13 15 18 8%x8% 8y 2 x8y 2 8y 2 x8y 2 8V 2 xl3 8y 2 xl3 13x13 13x17 17x21 %j 7x7 8y 2 x8y 2 8^x13 8V 2 X13 13x13 13x18 18x18 8 9 10 11 12 14 17 20 Round Flue Tile Lining 1 is listed by its inside measurement. Rectangular Lining 1 by outside Measurement. TABLE 11 Dimensions of Registers.* Size of opening, Inches Nominal area of opening, Square Inches Effective area of opening, Square Inches Tin Box Size, Inches Extreme dimensions of register face, Inches 6x10 60 40 63 ' x 10 T 9 5 7jl x lljj 8x10 80 53 85 i x 10H 8x12 96 64 /8 X 12% 9% x 13K 8x15 120 80 85 8 X 15% 9K x 1615 9x12 108 72 91 5 x 12JS IOH x 13% 9x14 126 84 9] 4 x 14H 10% x 16# 10x12 10x14 10x16 120 140 160 80 93 107 1014 x I2\l 101J x 1614 llli x 1318 1118 x 1518 1118 x 17% 12x15 180 120 123 4x15% 14^ x 17 12x19 228 152 12; 14^ x 21 14x22 308 205 14, 4 x 22% 16*4 x 24^ 15x25 375 250 15, /sx25% 16x20 320 218 16 ft x 20% 18 T 5 S x 22A 16x24 384 256 16, ft x24% ISA x 22& 20x20 400 267 2018 x 2018 22% x 22% 20x24 480 820 20, 8 x 241 i 22% x 26% 20x26 520 347 20 8 x 2618 22% x 28% 21x29 609 403 21 8 x 2918 28% x 81% 27x27 729 486 27- 8x2718 29% x 29% 27x38 80x30 1026 900 684 600 27- 80 8x3818 8 x 3018 29% x 403/g 32% x 32% Dimensions of different makes of registers vary slightly, Th above are for Tuttle & Bailey Manufacturing Oo.'s manufacture. *The Model Boiler Manual. 94 TABLE 15. Specific Heats, Coefficients of Expansion, Coefficients of Trans- mission, and Fuslng-Points of Solids, Liquids or Gases.* SUBSTANCE. o 2* C> 5? jM Coefficient of Expansion. Coefficient of Transmission Fusion Points Degrees Antimony 0.0508 0.0951 0.0324 0.1138 0.1937 0.1298 0.0314 0.0324 0.0570 0.0562 0.1165 0.1175 .00000602 .00000955 .00001060 .00000895 .00000478 .00000618 .00001580 .00000530 .00001060 .00001500 .00000600 .00000689 .00000003 .00001633 .00001043 .00000375 .00006413 .00007860 .00002313 .00012530 .00006806 .00003333 .00015151 .00022 .00404 815 1949 1947 2975 1832 2192 621 3452 1751 446 2507 2507 "787 1859 32 Copper Gold . Wrought Iron Glass .00089 .0000008 .000659 .00045 Cast Iron Lead Platinum Silver .00610 .00084 .00062 .00034 Tin . Steel (soft) Steel (hard) Nirkel steel 36% Zinc 0.0956 0.0939 0.5040 0.2026 0.2410 0.1970 0.1887 1.0000 0.0333 0.7000 .00170 .00142 .000024 "660602 .00203 "ooooos .00011 .000000 Brass Ice Sulphur Charcoal 1213 Aluminum _ Phosphorus Water Mercury :::: Alcohol (absolute) Con- stant Pres- sures Con- stant volume Coefficient of cubical ex- pansion at 1 atmos. Air 0.23751 0.21751 3.40900 0.24380 0.4805 0.2170 0.16847 0.15507 2.41226 0.17273 0.346 0.1535 .003671 .003674 .003669 .003668 .003726 .0000015 .0000012 .0000012 .0000012 "60006120 Oxygen Hydro gen Nitrogen Superheated Steam Carbonic Acid "Kent and Suplee. 295 TABLE 16. Capacities of \Varm Air Furnaces of Ordinary Construction Cubic Feet of Space Heated.* Divided Space Fire Pot Undivided Space +10 10 Diam. Area + 10 -10 12000 10000 8000 18 in. 1.8 sq. ft. 17000 14000 12000 14000 12000 10000 20 2.2 22000 17000 14000 17000 14000 12000 22 2.6 26000 22000 17000 22000 18000 14000 24 3.1 30000 -26000 22000 26000 22000 18000 26 3.7 85000 30000 26000 30000 26000 22000 28 4.8 40000 35000 30000 35000 30000 26000 30 4.9 50000 40000 35000 TABLE 17 Capacities of Hot-Air Pipes and Registers. ^ fl f-> M-t->j a h S** ^ w o 9 *5 H R 2 3 53 O w "eS & 09 c 1 III H 80, > . Ill O cc^ js 5iD S 11 6x8 6 in. 4x8 400 450 500 8x8 7 " 4x10 450 500 560 8x10 8 " 4x10 500 850 880 8x13 8 " 4x11 800 1000 1050 9x13 9 " 4x12 1050 1250 1324 9x14 9 " 4x14 1050 1350 1450 10x13 10 " 4x14 1500 1650 1800 10X14 10 " 6x10 1800 2000 2200 10x16 10 " 6x10 1800 2000 2200 12x14 12 " 6x12 2200 2300 2500 12x15 12 " 6x12 2250 2300 2500 12x17 12 " 6x14 2300 2600 2800 12x19 12 " 6x14 2300 2600 2800 14x18 14 " 6x16 2800 3000 3200 14x20 14 " 6x16 2900 3000 3200 14x22 14 " 8x16 3000 3200 3400 16x20 16 " 8x18 3600 4000 4250 16x24 16 " 8x18 3700 4000 4250 20x24 18 " 10x20 4800 5400 5750 20x26 20 " 10x24 6000 7000 7450 Federal Furnace League Handbook. tKidder's Arch and B'ld'rs Poclcet-Book. 296 TABLE 18. Air Heating: Capacity of Warm Air Furnaces.* Fire Pot Casing Total cross sec. area of heat pipes No. and size of heat pipes that may be supplied Diam. Area Diam. 18 i 20 i. 1.8 iq. 2.2 * ft. 30"-32" 34"-36" 180 sq 280 ( in. 3-9" or 4-8" 2-10" and 2-9" or 3-9" and 2-8" 22 2.6 86' '-40" 360 3-10" and 2-9" or 4-9" and 2-8" 24 3.1 4011.4411 470 3-10", 1-9" and 2-8" or 2-10" and 5-8" 26 3.7 44"-50" 565 5-10 and 3-9 or 3-10 , 4-9 and 2-8 28 4.3 48"-56" 650 2-12 , 3-10 and 3-9 or 5-10 , 3-9 and 2-8 30 4.9 52' '-60" 730 3-12 ,3-10 and 3-9 or 5- 10 ,5-9 and 1-8 TABLE 19. Sectional Area (Sq. Inches) of Vertical Hot Air Flues, Natural Draft, Indirect System.f Outside Temjperature 50 F. Flue Temperature 90 F. STEAM WATER Sq. Ft. Cast- Iron Radiation rd ^ mtt 0^ 2b ? O 33 S o o 2 -2 faze O2O2 HflQ fa72 Vll/1 faO2 to 50 TOO 75 63 60 75 63 60 60 60 75 150 113 94 80 113 94 80 80 75 100 200 150 125 100 150 125 100 100 100 125 250 188 156 125 188 156 125 125 12o 150 300 225 188 150 225 188 150 150 150 175 350 263 219 175 263 219 175 175 175 200 400 300 250 200 300 250 200 200 200 225 450 338 281 225 338 281 225 225 225 250 500 375 313 250 375 313 250 250 250 275 550 413 344 275 413 344 275 275 275 300 600 450 375 300 450 375 303 300 300 325 650 488 406 325 488 406 325 325 325 350 700 525 438 350 525 438 350 350 350 375 750 563 469 375 563 469 375 375 375 400 800 600 500 400 600 500 400 400 Velocity Feet Per Sec. * * * 1% 4 4 Effective Area of Register 1.00 1.50 1.83 2.17 1.00 1.00 1.33 1.33 Factor for *Federal Furnace League Handbook. tThe Model Boiler Manual. 297 TABLE 20. Pressure, in Ounces, per Square Inch Corresponding to Various Heads of Water, in Inches.* Decimal Parts of an Inch. Head in inches. .0 .1 .2 .3 .4 .5 .6 .7 .8 .9 .06 .12 .17 .23 .29 .35 :40 .46 .52 1 .58 .63 .69 .75 .81 .87 .93 .98 1.04 1.00 2 1.16 1.21 1.27 1.33 3.39 1.44 1.50 1.56 1.62 1.67 3 1.73 1.79 1.85 1.91 1.96 2.02 2.08 2.14 2.19 2.25 4 2.31 2.37 2.42 2.48 2.54 2.60 2.66 2.72 2.77 2.83 6 2.89 2.94 3.00 3.06 3.12 3.18 3.24 3.29 3.3J 3.41 6 3.47 3.52 3.58 3.64 3.70 3.75 3.81 3.87 3.92 3.98 7 4.04 4.10 4.16 4.221 4.28 4.33 4.39 4.45 4.50 4.56 8 4.62 4.67 4.73 4.79 4.85 4.91 4.97 5.03 5.08 5.14 9 5.20 5.26 5.31 5.37 5.42 5.48 5.54 5.60 5.66 5.72 TABLE 21. Height of Water Column, in Inches Corresponding to Pres- sures, in Ounces, per Square Inch.* Pressure in ounces Decimal Parts of an Ounce. >^ Q\J14O..LC; inch. .0 ,1 .2 .3 .4 .5 .6 .7 .8 .9 .17 .35 .52 .69 .87 1.04 1.21 1.38 1.56 l 1.73 1.90 2.08 2.25 2.42 2.60 2.77 2.94 3.11 3.29 2 3.48 3.63 3.81 3.98 4.15 4.33 4.50 4.67 4.84 5.01 3 5.19 5.36 5.54 5.71 5.88 6.06 6.23 6.40 6.57 6.75 4 6.92 7.09 7.27 7.44 7.61 7.79 7.96 8.13 8.30 8.48 5 8.65 8.82 9.00 9.17 9.34 9.52 9.69 9.86 10.03 10.21 6 10.38 10.55 10.73 10.90 11.07 11.26 11.43 11.60 11.77 11.95 7 12.11 12.28 12.46 12.63 12.80 12.97 13.15 13.32 13.49 13.67 8 13.84 14.01 14.19 14.36 14.53 14.71 14.88 15.05 15.22 15.40 9 15.57 15.74 15.92 16.09 16.20 16.45 16.62 16.70 16.96 17.14 *Suplee's M. E. Reference Book. 298 JOO j M j^ 9 MrtrHiHrHiHrHiHCOWOOCOOOOOWCOGOOOOOOOOOOOOOOOOOOO jooj lad looj Diqno 13 ~ - i S co 3> ' * tt M * 8> 1-4 r-l IH b S Oi C^ Ci CO rH xoaddy 299 TABLE 23. Expansion of Wrought-Iron Pipe on the Application of Heat.* Tern p. Air When Pipe is Fitted. Increase in Length in Inches Per 100 Feet When Heated to Degrees 160 180 200 212 220 228 240 274 Fahr. 1.28 1.44 1.60 1.70 1.76 1.82 1.93 2.19 32 1.02 1.18 1.34 1.44 1.50 1.57 1.66 1.94 50 .88 1.04 1.20 1.30 1.36 1.42 1.52 1.79 70 .72 .88 1.04 1.14 1.20 1.26 1.36 1.63 TABLE 24. Tapping: List of Direct Radiators.f STEAM. ONE-PIPE WORK. TWO-PIPE WORK. Radiator Area. Square Feet. Tapping Diam- eter. Inches. Radiator Area. Square Feet. Tapping Diam- eter. Inches. 24 24 60 60 100 100 and above 1 l!4 I* 48 48 96 96 and above 1 x % 114x1 l%xl% WATER. Tapped for* Supply and Return. Radiator Area. Square Feet. Tapping Diameter. Inches. 40 40 72 72 and above. 1 VA 1% *Holland Heating Manual, t American Radiator Co. 300 TABLE 25. Pipe Equalization. This table shows the relation of the combined area of small round warm air w ,-< <* eo M us us *> * ducts or pipes to the area of one ^ *! 2S^ large main duct. S^2 rn'rHiHiHiH rH^e* The bold figures at the top of the ,_ H * us os <=>>* us t-osr-i figures show the number ~ *&$* ***** of small pipes that each S_;_; ^ ^ ,_; .H' .-J tec4te main duct will supply. , _. ,. h.xample. 1 o supply six- teen 10-inch pipes: Refer to column having 10 at top; e ^eo^ob: esrHtoia smuat^e wooq follow down to small "^ IH I-H r4 rn ^ McioJoid >* ^^^ ficure 1 6 thence left on 1 *.<* . *. .** . ! . **:*.' . ^ ^ iiguic i y, ui iicc icu on t ~rHrH r nrHrHc4e&Jc4WM<>iieo^^ivft'> the horizontal line or e3 co^t-oorHc4iot--oMcooj-*Qqi the bold-face figure IH rn rn'M^dsi o * i-j that one 30-inch - r4 4i4 IH ei e eo '*'*-* uj 10 to o i> z> t> ed mam will sup- m e>i * & oq r-j eoiDCONio ocooooit- T-J us i-j so <* ply air for ^THrHrHrHd<^e4eoeo'*-*'*io>ooeDi>>a3 * "*OO3C4i COrH^OOlS t- T-) b- t- "HOiOrHO the sixteen ^ H t4 r40j co eo <* -* 10 ia 5 co ^ 06 06 d M 1 - inch M**^ t-ooooi cQt>r-HO i> r-j oq e "^^SSS oioes ''"'"^rH iHcie^ei^i coM- ad ooos c^ c* 'ft co r-j-^oqe^o i-jvisot--^ as o so IH os OI-HNSO-* oooo *~iHrH,_; Nuieicoeo' rji^ujiaco 6i>o6osc> ^ ^_ e t- co t>u5rij -*cO 01 rH T-ieifiievSCO -^Wiu5Ot> 00(35 b- N^rHoq t-cot-.eocs oco *",_,,_, (jJoiCOrJH^ USCOt-0001 i-i IH 04 coco^ioo j> a> us IH . t-H CO * US t- OS ss ^ c?c5^^S gSS; IgSSS ISI1I I i^s s^^sg mil iii|S ig||| | lllil S2*SS 51 ^t- m to i oo CD o - SSSS 301 TABLE 26. Capacities of Hot \Vater Risers in Square Feet of Direct Radiation.* Drop in Temperature 20. D. of Riser 1 F'l. 2 PI. 3 Fl. 4 Fl. 5 Fl. 6 Fl. Inches. % 32 IT 21 24 ] 22 32l 40 48 i*/i 38 56 70 80 88 iy 2 66 92 113 132: -145 2 140 196 238 280 310 2*A 240 328 400 470 515 3 350 490 595 700 770 850 m 510 705 860 1010 1110 1215 4 700 980 1190 1280 1540 1660 A small pipe should never be run to a great height where it only supplies one radiator. It is better to have limits for pipes as follows: D in inches: Height in feet: 45 (Reduce size by floors.) TABLE 27. Capacities of Pipes in Square Feet of Direct Steam Radiation. 3 i 1 C3 ij g-^g 02 03 a'*J^ a(N w w' ej o a^ oj'oB'o 03*0 G* cj G+J'O ,0 O 0$ 5 5 esS CO 1C Q ai5 Q Ccj H^ c* it? 1 l 36 60 5 3M, 3720 6200 1^4 i 72 120 6 sy% 6000 10000 1% 1% 120 200 7 4 9000 15000 2 i^ 280 480 8 4 12800 21600 S% 2 528 880 9 4% 17800 30000 3 2% 900 1500 10 5 23200 39000 3^ 8% 1320 2200 12 6 37000 62000 4 3 1920 3200 14 7 54000 92COO *K 3 2760 4600 16 8 76000 130000 international Correspondence School. tKent's M. E. Pocket-Book. 302 TABLE 28. Capacities of Hot Water Pipes in Square Feet of Direct Radiation.* JHJ Q^JS Indirect Radial' n Direct Radiation. Height of Coil above bottom of boiler, in ft. 10 ' 20 30 40 50 70 100 sq. ft. sq. ft. sq. ft. sq. ft. sq. ft. sq. ft. sq. ft. 3q. ft. % 49 50 62 53 55 57 61 68 1 87 89 93 95 98 101 108 121 144 ]36 140 144 149 153 158 169 189 i 1 ^ 196 20;: 209 214 222 228 243 271 2 349 359 370 380 393 405 433 483 tt 546 561 577 595 613 633 678 755 3 785 807 835 856 888 912 974 1086 3% 1069 1099 1133 1166 1202 1241 1327 1480 4 1395 1436 1478 1520 1571 1621 1733 1933 4V 2 1767 3817 1871 1927 1988 2052 2193 2445 5 3185 2244 2309 2876 2454 2531 2713 3019 6 3140 3228 3341 3424 3552 3648 3897 4344 7 4276 4396 4528 4664 4808 4964 5308 5920 8 5580 5744 5912 6080 6284 6484 6932 7735 9 7068 7268 7484 7708 7952 8208 8774 9780 10 8740 8976 9236 9516 9816 10124 10852 12076 11 10559 10860 11180 11519 11879 12262 13108 14620 13 12560 12912 13364 13696 14208 14592 155S8 17376 13 14748 15169 15615 16090 16591 17126 18307 20420 14 17104 17584 18109 18656 19232 19856 21232 23680 15 19634 20195 20789 31419 22089 22801 24373 27168 16 22320 22978 23643 24320 25136 25936 27728 30928 TABLE Capacities of Hot \Vater Mains Radiatioi 29. iii i.t Square Feet of Direct D. of mains . Total Estimated Length of Circuit. 100 200 300 400 500 600 700 800 900 1000 1 20 1% 35 20 1% 56 40 25 2 116 85 70 50 VA 220 150 120 100 90 s 345 240 SCO 170 150 140 125 110 100 90 3V 2 500 340 280 245 225 205 190 175 162 150 4 700 485 390 340 310 280 260 240 230 220 4% 925 640 535 460 410 37f 345 325 300 295 5 1200 830 700 600 540 490 450 420 400 380 6 1900 1325 1100 960 850 775 700 650 620 600 7 2000 1600 1400 1250 1140 1050 975 925 875 8 1970 1720 1550 1440 1350 1300 1260 9 1900 1800 1700 1620 *Kent's M. E. Pocket-Book. {International Correspondence School. 303 o s w 1 1 d T9A doj * b- TtiNC'50l>-COT i-H i ^.jx^^- i-l IM CO i-l M t- r-( t- jgd ^99^; otqno UT jo sso r i J9d 199^ ^99,1 UT PU9H JO SS01 a*^:< rH +j 03 s* 3 ^ 2} - r /l q ^ <1> rt fa a fll ~ 03 o 8* 4-> A\ S| o 8 . "|. o CJ 1 33 1 35 9 VI faM 35 7 4.34 35 7 5.37 35 7 6.45 35 8 4.96 40 8 6.14 40 8 7.37 40 9 5.58 45 9 6.91 45 9 8.29 45 10 6.20 50 10 7.68 50 10 9.21 50 11 6.82 55 11 8.45 55 11 10.13 55 12 7.44 60 12 9.22 60 12 11.05 60 18 8.06 65 13 9.99 65 13 11.97 65 14 8.68 70 14 10.76 70 14 12.89 70 15 9.30 75 15 11.53 75 15 13.81 75 36 9.92 80 16 12.30 80 16 14.73 80 17 10.54 85 17 13.07 85 17 15.65 85 18 11.16 90 18 13.84 90 18 16.57 90 19 11.78 95 19 14.59 95 19 17.50 95 20 12.40 100 20 15.36 100 20 18.42 100 *The Model Boiler Manual, t American Radiator Co. Combinations of the 40, 50, and 60 indh sections may be made if large free areas are required or the length of space is limited, thus, a 50, 60 combination of 10 sections gives a free area of 16.89 square feet. To figure the free area for any job, flivide the total cubic feet of air to be furnished per minute by the velocity per minute, which will give the free area in square feet. 307 TABLE 35. Percentage of Heat Transmitted by Various Pipe-Coverings, From Tests Made at Sifoley College, Cornell University, and at Michigan University.* Relative Amount Kind of Covering-. of Heat Transmitted. Naked pipe 100. Two layers asbestos paper, I in. hair felt, and canvas cover 15.2 Two alyers asbestos paper, 1 in. hair felt, canvas cover, wrapped with manilla paper 15 . Two layers asbestos paper, 1 in. hair felt 17. Hair felt sectional covering, asbestos lined 18.6 One thickness asbestos board 59.4 Four thicknesses asbestos paper 50.3 Two layers asbestos paper 77.7 Wool felt, asbestos lined 23.1 Wool felt with air spaces, asbestos lined 19.7 Wool felt, plaster paris lined 25.9 Asbestos molded, mixed with plaster paris 31.8 Asbestos felted, pure long 4 fibre 20.1 Asbestos and sponge 18.8 Asbestos and wool felt 20.8 Magnesia, molded, applied in plastic condition 22.4 Magnesia, sectional 18.8 Mineral wool, sectional 19.3 Rock wool, fibrous 20.3 Rock wool, felted 20.9 Fossil meal, molded, % inch thick 29.7 Pipe painted with black asphaltum 105.5 Pipe painted with light drab lead paint 108.7 Glossy white paint 95.0 'Carpenter's H. ?nd V. B. Note. These tests agree remarkably well with a series made by Prof. M. E. Cooley of Michigan University, and also with some made by G. M. Brill, Syracuse, N. Y., and reported in Transactions of the American, Society of Mechanical En- gineers, vol. XVI. 308 TABLE 36. Speeds, Capacities and Horse-Powers of "A B C" Steel Plate Fans at Varying Pressures. a] Pressures . N O N s 8 N H O * Q ^ 3* O iH 1-1 i O $ CO CU. FT. 2740 3900 4760 5490 6090 6700 7350 7750 8650 9520 30 R. P. M. S80 540 659 760 847 930 1004 1075 1200 1320 H. P. 0.80 1.60 2.66 3.85 5.32 6.65 8.22 10.25 14.38 18.85 CU. FT. 3550 5040 5490 7100 7910 8700 9410 10200 11210 1233o 36 R. P. M. 317 449 549 633 706 776 838 895 1000 1100 H. P. 1.03 2.05 3.42 4.95 6.84 8.54 10.60 13.2 18.45 24.3 CU. FT. 5220 7350 9050 10400 11600 12700 13750 14750 16500 18000 42 R. P. M. 271 383 471 542 605 663 716 768 857 938 H. P. 1.51 3.02 5.04 7.30 10.10 12.60 15.60 19.40 27.20 35.7 CU. FT. 6630 8900 10940 12550 14000 15350 16600 17800 19890 21920 48 R. P. M. 238 336 412 474 530 580 627 672 750 825 H. P. 1.82 3.65 1 6.06 8.82 12.15 15.20 18.85 23.40 32.80 43.2 CU. FT. 7850 11050 13600 15600 17450 19100 20650 22100 24750 27300 54 R. P. M. 211 299 366 421 470 515 557 596 666 734 H. P. 2.27 4.53 7.56 11.00 15.10 18,90 23.40 29.10 40.70 53.5 CU. FT. 9540 13500 16500 19050 21300 23300 25200 27000 30500 33000 60 R. P. M. 190 268 329 380 424 464 502 537 600 659 H. P. 2.76 5.52 9.20 13.35 18.42 23.00 28.60 35.90 49.60 65.2 CU. FT. 11870 16700 20600 23600 26400 28900 31300 33500 37500 41200 66 R. P. M. 173 2441 300 345 385 422 456 488 546 600 H. P. 3.43 6.85 11.44 16.60 22.90 28.60 35.50 44.00 61.7 81.2 CU. FT. 15000 21000 25840 29700 33200 36400 39400 42200 47103 51800 72 R. P. M. 159 224 274 316 354 387 418 448 500 550 H. P. 4.32 8.56 14.40 20.90 28.80 36.00 44.60 55.45 77.7 102.1 CU. FT. 19800 27900 34200 39400 44000 48200 51200 55800 63900 68400 84 R. P. M. 136 192 235 271 302 331 357 383 439 470 H. P. 5.72 11.421 19.00 27.60 38.10 47.60 59.00 73.30 102.7 135.5 CU. FT. 25050 35600 43700 50250 56150 61500 66500 71250 79200 87500 96 R. P. M. 118 168 206 237 265 290 314 336' 373 412 H. P. 7.29 14.60 24.32 35.20 48.60 60.75 75.30 93.50 134.0 172.0 CU. FT. 31410 44200 54300 62700 69700 76700 82700 88400 99000 108400 108 R. P. M. 109 149 183 211 235 259 279 298 334 366 H. P. 9.07 18.13 30.24 43.80 60.48 75.5 93.6 116.20 131. C 214.0 CU. FT. 38000 53700 66000 75700 84950 93000 100500 107200 12CX/X) 134000 120 R. P. M. 95 134 165 189 212 232 251 268 300 330 PI. P. 11.02 22.20 36.80 53.3 73.5 92.0 114.0 141.5 198.5 261.0 CU. FT. 46800 66300 80900 93200 104000 113500 123300 131400 ^47100 161500 132 R. P. M. 87 123 150 173 193 211 229 244 274 300 H. P. 13.48 27.00 44.90 65.10 89.6 112.0 1J9.0 173.0 243.0 318.0 CU. FT. 56400 79000 96500 12000 124800 136800 147400 158000 176100 194000 144 R. P. M. 80 112 137 159 177 194 209 224 250 275 H. P. 16.10 32.30 53.80 78.00 107.4 134.0 166.0 206.0 290.0 382.0 The capacities are based on the average results obtained when applied to the heating of buildings, and are reliable for such in- stallations. Three Quarter ounce pressure is common practice. 309 TABLE 37. Speeds, Capacities and Horse-Powers of "Green" Steel Plate Fans at Varying Pressures. i| Pressures 8 tsj o 8 af 8 N O g N O 44 o CU. FT. 2249 3176 3891 4498 5029 5513 5956 6372 7135 30 R. P. M. 330 466- 571 660 738 809 874 985 1047 H. P. .286 .811 1.491 2.298 3.213 4.227 5.311 6.515 9.120 CU. FT. 3239 4581 5605 6477 7242 7937 8584 9173 10268 36 R. P. M. 275 389 476 550 615 674 729 779 872 H. P. .413 1.170 2.148 3.311 4.625 6.080 7.681 9.376 13.125 CU. FT. 4398 6214 7617 8815 9864 10799 11679 12483 13981 42 R. P. M. 235 332 407 471 527 577 624 667 747 H. P. .557 1.576 2.898 5.473 6.300 8.287 10.4501 12.750 CU. FT. 5750 8123 9937 11500 12867 14123 15240 16301 18282 48 R. P. M. 206 291 356 412 461 506 546 584 655 H. P. .733 2.076 3.810 5.880 8.223 10.832 13.636 16.670 23.370 CU. FT. 7602 10758 13167 15203 17030 18650 20145 21558 24174 54 R. P, M. 183 259 sir 366 410 449 485 519 5S2 H. P. .970 2.750 5.047 7.767 10.880 14.300 18.017 21.992= 30.896 CU. FT. 9715 13718 16780 19429 21725 23786 25728 27495 307'92 60 R. P. M. 165 233 285 330 369 404 437 467 523 H. P. 1.241 3.506 6.433 9.932 13.882 18.230 22.996 28.077 39.355 CD. FT. 12078 17071 20855 24156 26975 29551 32047 34221 38247 66 R. P. M. 150 212 259 300 335 367 398 425 475 H. P. 1.542 4.361 7.996 12.352 17.238 22.666 28.675 35.123 48.895 CU. FT. 15608 21942 26918 31103 34835 38115 41169 44109 49312 72 R. P. M. 138 194 238 275 308 337 364 390 436 H. P. 1.983 5.601 10.322 15.881 22.252! 29.223 36.808 45.043 62.783 CU. FT. 20192 28405 34907 40383 45174 49452 53387 57152 63996 84 R. P. M. 118 166 204 236 264 289 312 334 374 H. P. 2.581 7.262 13.387 20.650 28.875 37.931 47.775 58.450 81.812 CU. FT. 23008 32614 39762: 46016 51601 56515 60983 65227 73045 96 R. P. M. 103 146 178 206 231 253 273 292 327 H. P. 2.941 8.337 15.261 23.531 32.982 43.348 54.511 66.707 93.380 CU. FT. 29260 41027 50568 58519 65198 71559 77284 82690 92549 108 R. P. M. 92 129 159 184 205 225 243 260 291 H. P. 3.737 10.488 19.397 30.060 41.666 54.871 69.163 84.556 118.291 CU. FT. 36209 51043 62384 71982 80270 88559 95539 102083 114298 120 R. P. M. 83 117 143 165 184 203 219 234 262 H. P. 4.628 13.050 23.925 36.807 51.307 67.928 85.495 104.401 146.116 CU. FT. 43560 61565 75504 87120 97575 106868 115580 123711 138231 132 R. P. M. 75 106 130 150 168 184 1991 213 238 H. P. 5.568 15.730 28.957 44.550 62.370 82.096 103.430 126.521 176.715 CU. FT. 52026 73138 89726 103298 116116 127426 137228 147030 164378 144 R. P. M. 69 97 119 137 154 169 182 195 218 H. P. 6.69 18.700 34.411 52.822 74.221 97.741 122.802 150.371 210.133 Note The hosre-power required to drive a fan will vary ac- cording to the manner of application. The horse-powers given above are 25 per cent, greater than would be required under ideal conditions. 310 TABLE 38. Speeds, Capacities and Horse-Powers of Sirocco Type Fans with No. 1 Blades, at Varying Pressures. Figures given represent dynamic pressures in ozs. per square inch. For static pressure deduct 28.8%. For velocity pressure deduct 71.2%. IDiam. [Wheel Pressures 8 g 8 ^? 8 s* g T-H | 3* H 6 ^ N O ^ N O c* M O i H Q n CU. FT. 155 220 2TO 310 350 380 410 440 490 540 6 R. P. M. 1145 1615 1980 2280 2560 2800 3005 3230 3616 3960 B. H. P. .0185' .052 .095 .147 .205 .270 .34 .42 .58 .76 CU. FT. 350 500 610 700 790 860 930 1000 1110 1220 9 R. P. M. 762 1076 1320 1524 1700 1866 2020 31521 2408 2040 B. H. P. .042 .118 .216 .333 .463- .610 .77 .95 1.3* 1.73 CU. FT. 625 880 1080 1250 1400 1530 1650 1770 1970 2170 12 R. P. M. 572 808 990 1145 1280 1400 1512 1615 1808 1980 B. H. P. .074 .208 .381 .588 .80 1.08 1.36 1.60 2.32 3.05 CU. FT. 975 1380 1690 1950 2180 2400 2590 2760 3090 3390 15 R. P. M. 456 645 790 912 1020 1120 1210 1290, 1444 1580 B. H. P. .115 .326 .600 .923 1.29 1.69 2.14 2.61 3.65 4.8 CU. FT. 1410 1990 2440 2820 3160 3450 3720 3980 4450 4830 18 R. P. M. 381 538 660 762 850 933 1010 1076| 1204 1320 B. H. P. .167 .470 .862 1.33 1.85 2.43 3.07 3.75 5.25 6.9 CU. FT. 1925 2710 3310 3850 4290 4700 5070 5420 6060 6620 21 R. P. M. 326 463 565 652 730 800 864 924 1032 1130 B. H. P. .227 640 1.17 1.81 2.53 3.33 4.18 5.11 7.15 9. A CU . FT . 2500 3540 4340 5000 5600 6120 6620 7080 7900 8680 24 R. P. M. 286 404 495 572 640 700 756 807 904 990 B. H. P. .296 .832 1.53 2.35 3.28 4.32 5.44' 6.64 9.3 ]2.2 CU. FT. 3175 4490 5500 6350 7100 7780 8400 8980 10050 11000 27 R. P. M. 254 359 440 508 568 622 673 718 804 88Q B. H. P. .373 1.05 1.94 2.98 4.16 5.48 6.90 8.44 11.8 15.fi CU. FT. 3910 5520 6770 7820 8750 9600 10350 11050 12330 13550 30 R. P. M. 228 322 395 456 510 560" 604 645 723 790 B. H. P. .460 1.30 2.40 3.68 5.15 6.75 8.53 10.4 14.5 19.1 CU FT. 5650 7950 9750 11300 12640 13800 14900 15900 178CO 19500 36 R. P. M. 190 269 330 381 425 466 504, 538 602 660 B. H. P. .665 1.87 3.44 5.30 7.40 9.72 12.29 15.0 20.9 27.5 CU . FT . 770 10850 13300 15400 17170 18800 20300 21700 24250 26600 42 R. P. M. 163 231 283 326 365 400 432 463 516 566 B. H. P. .903 2.55 4.69 7.24 10.1 13.3 16.7 20.4 28.5 87.5 311 II Q Pressures i o M N O S* N O N O g o N O ot 5 CU. FT. 10000 14150 17350 20000 22400 24500 26500 28300 31600 34700 48 R. P. M. 143 202 248 286 320 350 378 403 452 495 B. H. P. 1.18 3.32 6.10 9.40 13.1 17.2 21.75 26.0 37.1 48.8 CU. FT. 12700 17950 22000 25400 28400 31100 33600 35900 40200 44000 54 R. P. M. 127 179 220 254 284 311 336 359 4025 440 B. H. P. 1.49 4.20 7.75 11.9 16.6 21.9 27.6 ,33.7 47.1 62 CU. FT. 15650 22100 27100 31300 35000 38400 41400 44200 49400 54200 60 R. P. M. 114 161 198 228 255 280 302 322 sen. 396 B. H. P 1.84 5.20 9.58 14.7 20.6 27.0 34.1 41.6 58.2 76.5 CU. FT. 18950 26800 32850 37900 42300 46400 50100 53600 60000 65700 66 R. P. M. 104 147 180 208 232 254 275 294 328' 360 B. H. P. 2.23 6.30 11.6 17.8 24.9 32.7 41.2 50.4 70.4 92.6 CU. FT. 22600 31800 39000 45200 50600 55200 59600 63600 71200 78000 72 R. P. M. 95 134 165 190 212 233 253 269 301 330 B. H. P. 2.66 7.48 13.7 21.2 29.6 38.9 49.0 59.8 83.6 no CU. FT. 26400 37350 15800 52800 59100 64700 70000 74700 83500 91600 78 R. P. M. 88 124 15S 176 197 215 233 1 248 278 305 B. H. P. 3.10 8.77 16.1 24.8 34.7 45.6 57.5 70.2 98 129 CU. FT. 40800 i3400 1.3200 61600 38700 75200 812CO 86800 97100 L06400 84! R. P. M. 81 115 142 163 182 200 216 231 258 283 B. H. P. 3.61 10.2 18.7 28.9 40.4 63.0 66.8 81.7 114 150 CU. FT. 4 52St i9800 61000 70500 /8800 86400 93300 99600 111200 122000 90 R. P. M. 7t 107 133 152 170 186 201 214 241 264 B. H. P. 4.14 11.7 21.5 33.1 46.2 60.7 76.7 93.6 131 172 312 TABLE 39. Dimensions of Ells and Tees for Wrought Iron Pipe. SIZE E 1- 4- 4- 1 /, 5- 6- 6-34 l-t's TT/ 1- l-jl 4- 2-J4 2-% S-% 4- 6- 6-% i- i- i-y s 2- 2-% 4- 4-% Diagrams for Pipe Sizes and Friction Heads. To illustrate the use of the two following diagrams, ap- ply to the pipe line B, C, Art. 144. First, let I = 1500 feet, d = 8 inches and v = 5 feet per second. Trace along the velocity line until it intersects the diameter line, then fol- low the ordinate to the top of the page and find the friction head, 13 feet for 1000 foot run or 19.5 feet for the 1500 foot run. Second, let Q = 1.75 cubic feet per second and d = 8 inches. Trace to the left along the horizontal line represent- ing the volume of 1.75 cubic feet until it intersects the diameter line, then read up and find the same friction head as before. Third, let the allowable iriction head for 1500 feet of main be 19 feet, when Q = 1.75 cubic feet per second or when v = 5 feet per second. Reverse the process given above and find an 8 inch pipe. 313 as: ex- J-.: 5 rv O 5-3* - .= = o v ; \x ". u i*S^3s:id^ \ ,- 5i>:rs o Ltv % ' .> 314 315 INDEX Absolute pressure, 11 temperature, 10 Advantages of vac. systems, 169 Air, amount to burn carbon, 32 circulation, furnace system, 47 circulation within room, 69 composition, 14 exhausted from nozzle. 152 horse power in moving, 154 humidity of, 23 leakage, heat loss by, 37 needed, plenum system, 136 per person, table of, 21 required as heat carrier, 48 temperatures, plenum system, 142 valves, 91 velocity, plenum system, 136, 148 ventilating, per person, 19 washing and humidifying, 131 Anchors, types of, 192 Anemometer, 29 Appendix table 1 squares, cubes, etc., 271 table 2 properties of steam, 278 table 3 Naperian logarithms, 285 table 4 water conversion fac- tors, 285 table 5 volume and weight of dry air, 286 table 6 weight of pure water, 287 table 7 boiling points of water, 289 table 8 weight of water in air, 289 table 9 properties of air, 290 table 10 relative humidities, 291 table 11 fuel values Am. coal, 292 table 12 cap. of chimneys, 293 table 13 equalization of smoke flues, 294 table 14- diam. of registers, 294 table 15 specific heat, etc., of sub- stances, 295 tables 16, 18 capacities of furnaces, 296, 297 table 17 capacities of pipes and registers, 296 table 19 area vertical flues, 297 tables 20, 21 water pressures, 298 table 22 wrought iron pipes, 299 table 23 expansion of pipes, 300 table 24 tapping list of rad., 300 table 25 pipe equalization, 301 table 26 cap. hot water risers, 302 table 27 cap. steam pipes, 302 table 28 cap. hot water pipes, 303 table 29 cap. hot water mains, 303 tables 30, 31 sizes of steam mains, 304, 305 table 32 loss of head by friction of pipes, 306 table 33 expansion tanks, 307 table 34 sizes of Vento heaters, 307 table 35 heat trans, through pipe coverings, 308 tables 36, 37, 38 speeds, cap. h. p. of various fans, 309-312 table 39 dim. ells and tees, 313 Application of plenum system, 162 Area of ducts, plenum system, 136 Arrangement of Vento heaters, 145 of coils, plenum system, 144 Automatic vacuum sys., piping, 177 Automatic valves, 177 Basement plans, plenum sys., 165 Belvac thermofiers, 175 Blowers and fans, 119 speeds of, table, 158 work, Carpenter's rules, 155 Boilers, 223 feed pumps, 221 capacity and number of, 227 radiation supplied by, 224 Boiling point of water, table, 289 British thermal unit, 8 lost in plenum system, 140 Building material conductivities, 36 Calculating chimney area, 32 Calculating heat losses, 35 Calorie, 8 Carbon, amount of air to burn, 32 Carbon dioxide, per cent, table, 19 Carbon dioxide, tests for, 16 Carpenter's practical rules, 155 Cast radiators, 82, 84 Cast surfaces, plenum systems, 126 Centrifugal pumps, 219 Chart, hygrometric, 26 Chimneys, 33 capacity of, table, 293 Circulating duct in furnace design, 65 Circulating pumps, 216 Circulating water to condense steam, 209 Classification of radiators, 82 Coal, fuel values of. table, 292 Coil surface, plenum system, 124, 125, 129, 141 Combination heaters, 63 system, 87 Condensation, dripping from mains, 318 INDEX return to boilers, 110 Condenser for exhaust steam, 210 heating surface in, 211 Conduction, 12 Conductivities of building materi- als, 86 Conduits, central station htg., 185 Convection, 13 Conversion factors for water, 285 Data table for plenum systems, 164 Design, hot water and steam, 93 reports, instructions for 1, 2, 3, 258 reports, instructions for 4, 259 reports, instructions for 5, 261 Determination of pipe sizes, 99 Direct radiation, tapping list, table, 300 Dirt strainer, Webster, 173 District heating, 181 adaptation to private plants, 239 amount of radiation supplied, 208 amount supplied by reheater, 213 application to typical design, 239 boiler feed pumps, 221 by steam, 236 condensation from mains, 239 conduits, 185 cost of heating, 230 cost, summary of tests 232 diameter of mains, 205 economizers, 225 exhaust steam used in, 194, 210 future increase, 202 heating surface in reheater, 211, 213 high pressure steam heater, 216 important reheater details, 214 layout for conduit mains, 188 power plant layout, 231 pressure drop in mains, 203, 205, 237 radiation in district. 202 radiation supplied by 1 h. p. of ex. St., 209 regulation, 235 scope of work, 183 service connections, 207 steam available for heating, 207 systems classified, 182, 200 typical design, 193 velocity of water in mains, 205 Division of coils, plenum sys., 129 Ducts, furnace, cold air, 53 plenum system, 129, 130 recirculating, 65 Economizers, 225 radiation supplied by, 225 surface, 226, 227 Efficiency of plenum coils, table, 139 Electrical heating, 253 formulas used in, 253 Exhaust stepm available in district plants, 194-199 Exhaust steam condenser, 210 Expansion joints, 190 tanks, 92 Exposure heat losses, table, 38 Factor table, velocity and vol., 152 Fans and blowers.. 70, 119 drives, 157 housings, 121 power of engine for, 159 Fire places, stoves, etc., 117 Fittings, steam and hot water, 89 Floor plans for furnace heating, 106-108 Floor plans for plenum sys., 165-167 Formulas, empirical for radiation, 96 Fresh air duct, 53-64 Fresh air entrance to bldgs., 123 Fuel values of Am. coals, table, 292 Furnace, air circulation within room, 69 foundations, 64 heating, 45 location, 64 selection, 60 Furnace system, air circulation, 47 air required as heat carrier, 47 circulating duct in, 65 design of, 55 essentials of, 46 fan in, 70 fresh air duct in, 53, 64 grate area in, 63 gross register area in, 51 heat stacks, sizes of, 51, 67 heating surface in, 54 leader pipes in, 52, 66 net vent register in, 51 plans for, 57 points to be calculated in, 47 registers, temperatures in, 50 stacks or risers in, 67 three methods of installation, 49 vent stacks, 69 Gage pressures, 11 Grate area, boilers and heaters, 101 Grate area for furnaces, 53 Greenhouse heating, 97 Hammer, water, 110 Heat given off by persons, lights, etc., 43 latent, 11 measurement of, 8 mechanical equivalent of, 11 stacks, sizes of, 51, 67 Heaters, hot water, 87 Heating, district, cost of, 230 Heating surface in coils, plenum sys- tem, 137 INDEX 319 Heating sur., in economizer, 226, 227 in furnace system, 54 in reheater, 211 per h. p. in reheater, 213 Heat loss, 37, 38, 39, 41, 134 calculation of, 35 combined, 41 for a 10 room house, table, 56 High pressure heater, 216 High pressure steam trap, 110 Horse power, in moving air, 154, 155 of engine for fan, 159 required to move air in plenum system, 150 Hot air pipes, cap. of, table, 296 water heaters, 87 water pipes, capacity of, table, 302 water radiators, 85 water risers, cap. of, table, 303 water system, 72 water used in indirect coils in ple- num, system, 146 Hot water and steam heating, calculations for rad. sur. for, 93 classifications, 75 determination of pipe sizes for, 99 empirical formula for, 96 grate area for heater, 101 greenhouse radiation, 97 location of radiators for, 102 parts of, 73 pitch of mains for, 102 principles of design of, 93 second classification of, 76 typical layout of, 103 Humidity of the air, 23 Humidities, relative, table, 291 Hygrodeik, 24 Hygrometer, 23 Hygrometric chart, 26 Indirect radiators, 76 Installation of steam pipes, 109 Instructions for design reports, Nos. 1, 2, 3, 258 for design report, No. 4, 259 for design report, No. 5, 261 'K,' values for pipe coils, table, 139 'K,' values for Vcnto coils, table, 141 outline of course in, 257 suggestions for course in, 256 Latent heat, 11 Layout for furnace system, 106 for hot water heating plant, 103 for plenum system, 127, 128 of power plant, 231 steam mains and conduits, 188 Leader pipes, 52, 66 Location of furnaces, 64 of radiators, 102 Low pressure steam traps, 110 Mains, condensation, dripping from, 239 cap. of hot water, table, 303 diameter of, 205 pitch of, 102 pressure drop and diameter of, 237 velocity of water in, 205 Manholes, 193 Measurement o,f air velocities, 29 of heat, 8 of high temperatures, 9 Mechanical vacuum steam htg. sys., advantages of, 169 automatic pump for, 172 Automatic system, 177 Paul system, 177 principal features of, 170 Van Auken, 175 Webster system, 173 Mechanical equivalent of heat, 11 Mechanical warm air heating and ventilating sys., 117, 133, 148 blowers and fans for, 119 definitions of terms, 133 elements of, 117 exhaust, 118 heat loss and cu. ft. air exhausted, 134 theoretical considerations for, 133 variations in design of, 118 Mills system (attic main), 78 Modulation valve for Webster Bys- tem, 175 Moisture, addition of, to air, 27 with air, 22 Naperian logarithms, table, 285 Nitrogen, 15 'n,' values of, 41 Operation of hot water heaters and boilers, of furnaces, 70 suggestions for. 114 Oxygen, 15 Paul sys. of mech. vac. heating, 177 typical piping connections for, 178 Pipe coil radiators. 83 capacity of, in sa. ft. of steam radiation, 302 equalization, table of, 301 sizes, determination of, 99 Pipe, leader, 52, 66 Piping connection around heater and engine, 161 connections for auto. vac. sys., 177 connections for Paul sys., 178 for heatg. sys. definitions, 74 system for automatic control of, Webster system, 175 Pitot tubes, 30 Plans and sped, for htg. sys., 263 typical specifications, 264 318 INDEX return to boilers, 110 Condenser for exhaust steam, 210 heating surface in, 211 Conduction, 12 Conductivities of building materi- als, 86 Conduits, central station htg., 185 Convection, 13 Conversion factors for water, 285 Data table for Dlenum systems, 164 Design, hot water and steam, 93 reports, instructions for 1, 2, 3, 258 reports, instructions for 4, 259 reports, instructions for 5, 261 Determination of pipe sizes, 99 Direct radiation, tapping list, table, 300 Dirt strainer, Webster, 173 District heating, 181 adaptation to private plants, 239 amount of radiation supplied, 208 amount supplied by reheater, 213 application to typical design, 239 boiler feed pumps, 221 by steam, 236 condensation from mains, 239 conduits, 185 cost of heating, 230 cost, summary of tests 232 diameter of mains, 205 economizers, 225 exhaust steam used in, 194, 210 future increase, 202 heating surface in reheater, 211, 213 high pressure steam heater, 216 important reheater details, 214 layout for conduit mains, 188 power plant layout, 231 pressure drop in mains, 203, 205, 237 radiation in district, 202 radiation supplied by 1 h. p. of ex. st., 209 regulation, 235 scope of work, 183 service connections, 207 steam available for heating, 207 systems classified, 182, 200 typical design, 193 velocity of water in mains, 205 Division of coils, plenum sys., 129 Ducts, furnace, cold air, 53 plenum system, 129, 130 recirculating, 65 Economizers, 225 radiation supplied by, 225 surface, 226, 227 Efficiency of plenum coils, table, 139 Electrical heating, 253 formulas used in, 253 Exhaust steam available in district plants, 194-199 Exhaust steam condenser, 210 Expansion joints, 190 tanks, 92 Exposure heat losses, table, 38 Factor table, velocity and vol., 152 Fans and blowers.. 70, 119 drives, 157 housings, 121 power of engine for, 159 Fire places, stoves, etc., 117 Fittings, steam and hot water, 89 Floor plans for furnace heating, 106-108 Floor plans for plenum sys., 165-167 Formulas, empirical for radiation, 96 Fresh air duct, 53-64 Fresh air entrance to bldgs., 123 Fuel values of Am. coals, table, 292 Furnace, air circulation within room, 69 foundations, 64 heating, 45 location, 64 selection, 60 Furnace system, air circulation, 47 air required as heat carrier, 47 circulating duct in, 65 design of, 55 essentials of, 46 fan in, 70 fresh air duct in, 53, 64 grate area in, 63 gross register area in, 51 heat stacks, sizes of, 51, 67 heating surface in, 54 leader pipes in, 52, 66 net vent register in, 51 plans for, 57 points to be calculated in, 47 registers, temperatures in, 50 stacks or risers in, 67 three methods of installation, 49 vent stacks, 69 Gage pressures, 11 Grate area, boilers and heaters, 101 Grate area for furnaces. 53 Greenhouse heating, 97 Hammer, water, 110 Heat given off by persons, lights, etc., 43 latent, 11 measurement of., 8 mechanical equivalent of, 11 stacks, sizes of, 51, 67 Heaters, hot water, 87 Heating, district, cost of, 230 Heating surface in coils, plenum sys- tem, 137 INDEX Heating sur., in economizer, 226, 227 in furnace system, 54 in reheater, 211 per h. p. in reheater, 213 Heat loss, 37, 38, 39, 41, 134 calculation of, 35 combined, 41 for a 10 room house, table, 56 High pressure heater, 216 High pressure steam trap, 110 Horse power, in moving air, 154, 155 of engine for fan, 159 required to move air in plenum system, 150 Hot air pipes, cap. of, table, 296 water heaters, 87 water pipes, capacity of, table, 302 water radiators, 85 water risers, cap. of, table, 303 water system, 72 water used in indirect coils in ple- num system, 146 Hot water and steam heating, calculations for rad. sur. for, 93 classifications, 75 determination of pipe sizes for, 99 empirical formula for, 96 grate area for heater, 101 greenhouse radiation, 97 location of radiators for, 102 parts of, 73 pitch of mains for, 102 principles of design of, 93 second classification of, 76 typical layout of, 103 Humidity of the air, 23 Humidities, relative, table, 291 Hygrodeik, 24 Hygrometer, 23 Hygrometric chart, 26 Indirect radiators, 76 Installation of steam pipes, 109 Instructions for design reports, Nos. 1, 2, 3, 258 for design report, No. 4, 259 for design report, No. 5, 261 'K,' values for pipe coils, table, 139 'K,' values for Vcnto coils, table, 141 outline of course in, 257 suggestions for course in, 256 Latent heat, 11 Layout for furnace system, 106 for hot water heating plant, 103 for plenum system, 127, 128 of power plant, 231 steam mains and conduits, 188 Leader pipes, 52, 66 Location of furnaces. 64 of radiators. 102 Low pressure steam traps, 110 Mains, condensation, dripping from, 239 cap. of hot water, table, 303 diameter of, 205 pitch of, 102 pressure drop and diameter of, 237 velocity of water in. 205 Manholes, 193 Measurement of air velocities. 29 of heat. 8 of high temperatures, 9 Mechanical vacuum steam htg. sys., advantages of. 169 automatic pump for, 172 Automatic system, 177 Paul system, 177 principal features of, 170 Van Auken, 175 Webster system, 173 Mechanical equivalent of heat, 11 Mechanical warm air heating and ventilating sys., 117, 133, 148 blowers and fans for, 119 definitions of terms, 133 elements of, 117 exhaust, 118 heat loss and cu. ft. air exhausted, 134 theoretical considerations for, 133 variations in design of, 118 Mills system (attic main), 78 Modulation valve for Webster sys- tem, 175 Moisture, addition of, to air, 27 with air. 22 Naperian logarithms, table, 285 Nitrogen, 15 'n,' values of, 41 Operation of hot water heaters and boilers, of furnaces, 70 suggestions for. 114 Oxygen, 15 Paul sys. of mech. vac. heating, 177 typical piping connections for, 178 Pipe coil radiators. 83 capacity of, in sa. ft. of steam radiation, 302 equalization, table of. 301 sizes, determination of, 99 Pipe, leader, 52, 66 Piping connection around heater and engine, 161 connections for auto. vae. sys., 177 connections for Paul sys., 178 for heatg. sys. definitions, 74 system for automatic control of, Webster system, 175 Pitot tubes, 30 Plans and speci. for htg. sys., 263 typical specifications, 264 320 INDEX Plenum system, actual amount of air exhausted in, 152 air needed cu. ft. per hour in, 136 air velocity, table, 136 air velocity theoretical in, 148 air washing and humidifying, 131 amount of steam condensed, 146 application of to school bldgs., 162 approximate rules for, 142 approximate sizes of fan wheels, table, 156 arrangement of coils in pioe heat- ers, 144 arrangement of sees, and stacks in Vento heaters, 145 basement plans for, 165 blower fans actual h. D. to move air, 155 Carpenter's rules for, 155 cast surface for, 126 coil surface in, 124, 125 cross sectional area ducts, regis- ters, etc., 136 data, table, 164 division of coil surface in, 129 double ducts in, 130 dry steam needed in excess of exh. from engine, 147 efficiency and air temp., table 139 factors for change of velocity and volume, table, 152 fan drives for, 157 final air temperature in, 142 floor plans for, 165-167 heating surface in coils of, 137 heating surfaces, 124 h. p. of engine for fan for, 159 h. p. to move air, table, 150 'K,' values of, 138 layout, 127, 128 piping connections around heater and engine, 161 pressure and velocity, results of tests of, 153 single duct in, 129 speed of blower fans, table, 158 speed of fans for, 157 temp, of air at register in, 135 temp, of air leaving coils, 143 total B. t. u. transmitted per hr., table, 140 use of hot water in indirect coils, 146 values of 'K,' 138 velocity of air escaping to atmos- phere, table, 151 work done in moving air, 154 Power plant layout, 231 Pressed steel radiators, 84 Pressure, absolute, 11 and velocity, results of tests, 153 gage, 11 in ounces per SQ. in., table, 298 water in mains, 203 Principal features of mechanical vac- uum heating system, 170 Properties of air, 290 Properties of steam, table, 278 Pumps, boiler feed, 221 centrifugal, 219 circulating, 216 city water supply, 221 for mech. vac. steam heating, 172 Radiation, 12 amount of one sa. ft. reheater tube surface will supply, 213 amt. supplied by economizer, 225 amt. supplied by one h. p., 224 hot water, 85 one Ib. exh. steam will supply, 208 supplied by 1 h. p. exh. steam, 209 sur. to heat circulating water, 226 surface to heat feed water, 227 Radiators, amt. of surface on, 86 cast, 83, 84 classification of, 82 columns of, 83 direct, 75 direct-indirect, 75 height of, 85 indirect, 76 location and connection of, 102 pipe coil, 83 pressed steel, 84 sizes, etc., for ten room house, table, 105 sizes, table of, 86 steam, 85 surface calculation for, 93 sur. effect on trans, of heat, 86 Recirculating duct, 65 Register, area of. 51 diameter of. table, 294 ducts, area of, 136 sizes, net heat, 50 temperature, 50 Regulation, district heating, 235 Sylph on damper, 245 Room temperature, standard, 42 Service connections, 207 Single duct, plenum system, 129 Sizes of fan wheels, approximate, table, 156 Smoke flues, equalization of, 294 Specifications for plans, 257, 264 Specific heat, 12 heats, etc., of substances, 295 Speeds of blower fans, 157, 158 Squares, cubes, etc., table, 271 Stacks and risers. 67 Standard room temperature, 42 Steam and hot water fittings, 89 available for heating circulating water, 207 boilers, 87 INDEX condensed per SQ. ft. of heating sur. per hour, plenum sys., 146 dryf needed in excess of engine exhaust, 147 heater, high pressure, 216 heating, district, 236 pipe installation, 109 radiators, 85 traps, high pressure, 110 Steam system, 72 amt. condensed in plenum sys., 146 classification, 75 parts of, 73 second classification of, 76 Street mains and conduits, layout, 188 Suggestions for operating hot water heaters and boilers, 114 for operating furnaces, 70 Sylphon damper regulator, 245 Table I determination of COa, 19 Tables II, III volume of air per per- son, 21 Table IV conductivities of materials, 36 Table V exposure losses. 38 Table VI values of t 1 , 42 Table VII values of t=> , 43 Table VIII heat given off by per- sons, lights, etc., 43 Table IX application, to 10 room res., 56 Table X size and sur. of rads., 86 Table XI temi>. of water in mains, 99 Table XII summary, h. w. htg., 105 Table XIII vel. in plenum sys., 136 Tables XIV-XVII efficiencies of coils, 139-141 Tables XVIII-XIX temp, of air on leaving coils, 143 Tables XX-XXII air pressure and velocity, 150-152 Table XXIII sizes of fans. 156 Table XXIV speeds of fans, 158 Table XXV data for plenum sys., 164 Table XXVII pressure of water in mains, 205 Table XXVIII cal. of conduit mains, 241 Table Table Table Table Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11 squares, cubes, etc., 271 properties of steam, 278 Naperian logarithms, 285 water conversion factors, 285 vol. and wt. of dry air, 286 weight of pure water, 287 boiling points of water, 289 weight of water and air, 289 properties of air, 290 relative humidities, 291 fuel values of Am. coal, 292 Table 12 capacities of chimneys, 293 Table 13 equalization of smoke flues, 294 Table 14 diameter of registers, 294 Table 15 sp. ht., etc., of substances, 295 Tables 16, 18 cap. of fur., 296, 297 Table 17 cap. of pipes and reg., 296 Table 19 area vertical flues, 297 Table 20, 21 water pressures, 298 Table 22 wrought iron pipes, 209 Table 23 expansion of pipes, 300 Table 24 tapping list of rad., 300 Table 25 pipe equalization, 301 Table 26 capacities 1 of hot water risers, 302 Table 27 cap. of steam pipes, 302 Table 28 cap. of hot water pipes, 303 Table 29 cap. of hot water mains, 303 Tables 30 31 sizes of steam mains. 304 305 Table 32 loss of head by friction ol pipes, 306 Table 33 expansion tanks, 307 Table 34 sizes of Vento heaters, 307 Table 35 heat trans, through pipe coverings, 308 Tables 36, 37, 38 speeds, cap. h. p. of various' fans, 309-312 Table 39 dim. of ells and tees, 313 Tanks, expansion, 92 Temperature absolute, 10 measurement of high, 9 of air entering plenum system, 135 of air in greenhouses, table, 99 ol air leaving coils in plenum sys- tem, 143 room standard, 42 Temp, control in heating sys., 243 Andrews system, 244 important points in, 247 in large plants, 246 Johnson system, 248 thermostat, 244 National system, 251 Powers system, 249 principle of system, 243 special designs of, 247, 252 Sylphon damper control, 245 Thermofiers, Belvac, 175 Thermostat, 244 thermostatic valve. 174 Traps, high pressure steam, 110 low pressure steam, 110 Under- fed furnaces. 62 Use of hot water in indirect coils 146 Vacuum systems, 79, 169 Values of V. 140 of 'k,' 36, 141 of 'n.' 41 Of 't.' 42, 43 INDEX Valves, air. 91 automatic vacuum. 177 modulation valve. 175 thennostatic, 174 types of, 192 Velocity of air by application of heat, 28 of air escaping to atmosphere, 151 Vent registers (net), 51 stacks, 69 Ventilation heat loss. 88 air required per person, 19 Vento coils, values of 'k' for. 141 Vertical hot air flues, table. 297 Volume and wt. of dry air, table, 286 Warm air fur., cap. of, table 296 air heating cap., 297 Washing and humidifying of air, 131 Water, conversion factors, table. 285 hammer, 110 needed per hour in dist. htg., 201 pressure in mains. 203 pressure, table of. 205 seal motor, Webster. 173 weight of column corresponding to air pressure in ozs.. 298 weight of pure, table of. 287 weight of water and air. table, 289 Weight of pure water, 287 of water and air. table. 289 Work done in moving air, 154 Wrought iron and steel pipes, table, 299 expansion of. table, 300 UNIVERSITY OF CALIFORNIA LIBRARY