NRLF B M 5E 1 4 271 LIBRARY UNIVERSITY OF CALIFORNIA. Class PRINCIPLE OF HOT WATER HEATING ILLUSTRATED BY TRANSVERSE SECTIONAL VIEW SHOWING BOILER, RADIATOR AND EXPANSION TANK. American Radiator Company. Heating and Ventilation A Working Manual of APPROVED PRACTICE IN THE HEATING AND VENTILATING OF DWELLING- HOUSES AND OTHER BUILDINGS, WITH COMPLETE PRACTICAL IN- STRUCTION IN THE MECHANICAL DETAILS, OPERATION, AND CARE OF MODERN HEATING AND VENTILATING PLANTS By CHARLES L. HUBBARD, S. B., M. E. Consulting Engineer on Heating, Ventilating, Lighting, and Power ILLUSTRATED OF THE UNIVERSITY OF CHICAGO AMERICAN SCHOOL OF CORRESPONDENCE 1909 GENERAL COPYRIGHT 1908 BY AMERICAN SCHOOI, OF CORRESPONDENCE Entered at Stationers' Hall, L,ondon All Rights Reserved Foreword recent years, such marvelous advances have been made in the engineering and scientific fields, and so rapid has been the evolution of mechanical and constructive processes and methods, that a distinct need has been created for a series of practical working guides, of convenient size and low cost, embodying the accumulated results of experience and the most approved modern practice along a great variety of lines. To fill this acknowledged need, is the special purpose of the series of handbooks to which this volume belongs. C, In the preparation of this series, it has been the aim of the pub- lishers to lay special stress on the practical side of each subject, as distinguished from mere theoretical or academic discussion. Each volume is written by a well-known expert of acknowledged authority in his special line, and is based on a most careful study of practical needs and up-to-date methods as developed under the conditions of actual practice in the field, the shop, the mill, the power house, the drafting room, the engine room, etc. C, These volumes are especially adapted for purposes of self- instruction and home study. The utmost care has been used to bring the treatment of each subject within the range of the com- 179734 mon understanding, so that the work will appeal not only to the technically trained expert, but also to the beginner and the self- taught practical man who wishes to keep abreast of modern progress. The language is simple and clear; heavy technical terms and the formulae of the higher mathematics have been avoided, yet without sacrificing any of the requirements of practical instruction; the arrangement of matter is such as to carry the reader along by easy steps to complete mastery of each subject; frequent examples for practice are given, to enable the reader to test his knowledge and make it a permanent possession; and the illustrations are selected with the greatest care to supplement and make clear the references in the text. C. The method adopted in the preparation of these volumes is that which the American School of Correspondence has developed and employed so successfully for many years. It is not an experiment, but has stood the severest of all tests that of practical use which has demonstrated it to be the best method yet devised for the education of the busy working man. C, For purposes of ready reference and timely information when needed, it is believed that this series of handbooks will be found to meet every requirement. Table of Contents SYSTEMS OF HEATING ._ Page 1 Stoves Hot-Air Furnaces Direct and Indirect Steam Heating Direct- Indirect Radiators Direct and Indirect Hot-Water Heating Exhaust Steam Heating Forced Blast Heating Electric Heating Principles of Ventilation Composition of Atmosphere Quantity of Air Required Force for Moving Air Measurements of Velocity Air Distribution Heat Loss from Buildings DETAILS, CARE, AND MANAGEMENT OF APPARATUS . . ,. Page 19 Types of Furnaces (Direct- and Indirect-Draft) Furnace Details (Grate, Firepot, Combustion Chamber, Radiator, Heating Surface, Efficiency, Heat- ing Capacity) Location of Furnace Smoke-Pipe Chimney Flue Cold- Air Box Return Duct Warm-Air Pipes Registers Combination Sys- tems Care and Management of Furnaces Steam Boilers (Tubular and Sectional) Water-Tube Boilers Horse- Power for Ventilation Radiators for Direct Steam (Cast-Iron and Pipe) Circulation Coils Efficiency of Radiators, Coils, etc. Systems of Piping (Two-Pipe, One-Pipe Relief, One- Pipe Circuit) Radiator Connections Expansion of Pipes Valves (Angle, Offset, Corner, Globe) Air-Valves Pipe Sizes Calculating Flow of Steam Calculating Heating Surface Supplied Boiler Connections Sizes for Re- turn, Blow-Off, and Feed Pipes Blow-Off Tank Types of Indirect-Steam Heaters Efficiency of Heaters Stacks, and Casings Dampers Warm-Air Flues Cold-Air Ducts Vent Flues Registers Pipe Connections Direct- Indirect Radiators Care and Management of Boilers Types of Direct Hot-Water Heaters Direct Hot-Water Circulation Direct Hot-Water Radiators Hot- Water Piping Overhead Distribution Expansion Tank Air-Venting Hot-Water Pipe Connections Valves and Fittings Types of Indirect Hot-Water Radiators Size of Stacks Flues and Casings Care and Management of Hot-Water Heaters Forced Hot-W T ater Circulation Single-Pipe and Circuit Systems of Piping Sizes of Mains and Branches Pumps Pipe Flow Friction Head Exhaust-Steam Heating Reducing Valves Grease Extractor for Exhaust Steam rBack-Pressure Valve Ex- haust Head Return-Pumps Balance Pipe Return Traps Damper Regu- lators Vacuum or Low-Pressure Systems (Webster, Paul) SYSTEMS OF VENTILATION Page 147 Forced Blast (Exhaust and Plenum Methods) Form of Heating Surface - Centrifugal Fans or Blowers Disc Fans or Propellers General Proportions Exhausters Fan Speeds and Pressures Velocities of Air-FlowBlast Area Resistance Power Required Capacity, Speed, etc., of Disc Fans Fan Engines and Motors Factory Heating Double-Duct System Electric Heating Calculation and Construction of Electric Heaters Temperature Regulators Diaphragm Motors Dampers Telethermometer Humidostat Air Filters and Washers Heating and Ventilating of Schools, Hospitals, Churches, Office Buildings, Apartment Houses, Conservatories, etc. INDEX , . v . Page 215 HOT WATER HEATER AND CONNECTIONS. HEATING AND VENTILATION PART I SYSTEMS OF WARMING Any system of warming must include, first, the combustion of fuel, which may take place in a fireplace, stove, or furnace, or a steam, or hot-water boiler; second, a system of transmission, by means of which the heat may be carried, with as little loss as possible, to the place where it is to be used for warming; and third, a system of dif- fusion, which will convey the heat to the air in a room, and to its walls, floors, etc., in the most economical way. Stoves. The simplest and cheapest form of heating is the stove. The heat is diffused by radiation and convection directly to the objects and air in the room, and no special system of transmission is required. The stove is used largely in the -country, and is especially adapted to the warming of small dwelling-houses and isolated rooms. Furnaces. Next in cost of installation and in simplicity of operation, is the hot-air furnace. In this method, the air is drawn over heated surfaces and then transmitted through pipes, while at a high temperature, to the rooms where heat is required. Furnaces are used largely for warming dwelling-houses, also churches, halls, and schoolhouses of small size. They are more costly than stoves, but have certain advantages over that form of heating. They require less care, as several rooms may be warmed from a single furnace; and, being placed in the basement, more space is available in the rooms above, and the dirt and litter connected with the care of a stove are largely done away with. They require less care, as only one fire is necessary to warm all the rooms in a house of ordinary size. One great advantage in the furnace method of warming comes from the constant supply of fresh air which is required to bring the heat into the rooms. While this is greatly to be desired from a sanitary stand- point, it calls for the consumption of a larger amount of fuel than would otherwise be necessary. This is true because heat is required to warm the fresh air from out of doors up to the temperature of the HEATING AND VENTILATION rooms, in addition to replacing the heat lost by leakage and conduction through walls and windows. A more even temperature may be maintained with a furnace than by the use of stoves, owing to the greater depth and size of the fire, which allows it to be more easily controlled. When a building is placed in an exposed location, there is often difficulty in warming rooms on the north and west sides, or on that side toward the prevailing winds. This may be overcome to some ex- tent by a proper location of the furnace and by the use of extra large pipes for conveying the hot air to those rooms requiring special at- tention. Direct Steam. Direct steam, so called, is widely used in all classes of buildings, both by itself and in combination with other systems. The first cost of installation is greater than for a furnace; but the amount of fuel required is less, as no outside air supply is necessary. If used for warming hospitals, schoolhouses, or other buildings where a generous supply of fresh air is desired, this method must be supplemented by some form of ventilating system. One of the principal advantages of direct steam is the ability to heat all rooms alike, regardless of their location or of the action of winds. When compared with hot-water heating, it has still another desirable feature which is its freedom from damage by the freezing of water in the radiators when closed, which is likely to happen in unused rooms during very cold weather in the case of the former system. On the other hand, the sizes of the radiators must be proportioned for warming the rooms in the coldest weather, and unfortunately there is no satisfactory method of regulating the amount of heat in mild weather, except by shutting off or turning on steam in the radia- ators at more or less frequent intervals as may be required, unless one of the expensive systems of automatic control is employed. In large rooms, a certain amount of regulation can be secured by dividing the radiation into two or more parts, so that different combinations may be used under varying conditions of outside temperature. If two radiators "are used, their surface should be proportioned, when convenient, in the ratio of 1 to 2, in which case one-third, two-thirds, or the whole power of the radiation can be used as desired. HEATING AND VENTILATION Indirect Steam. This system of heating combines some of the advantages of both the furnace and direct steam, but is more costly to install than either of these. The amount of fuel required is about the same as for furnace heating, because in each case the cool fresh air must be warmed up to the temperature of the room, before it can become a medium for conveying heat to offset that lost by leakage and conduction through walls and windows. A system for indirect steam may be so designed that it will supply a greater quantity of fresh air than the ordinary form of furnace, in which case the cost of fuel will of course be increased in proportion to the volume of air supplied. Instead of placing the radiators in the rooms, a special form of heater is supported near the basement ceiling and encased in either galvanized iron or brick. A cold-air supply duct is connected with the space below the heater, and warm air pipes are taken from the top and connected with registers in the rooms to be heated the same as in the case of furnace heating. A separate stack or heater may be provided for each register if the rooms are large; but, if small and so located that they may be reached by short runs of horizontal pipe, a single heater may serve for two or more rooms. The advantage of indirect steam, over furnace heating comes from the fact that the stacks may be placed at or near the bases of the flues leading to the different rooms, thus doing away with long, horizontal runs of pipe, and counteracting to a considerable extent the effect of wind pressure upon exposed rooms. Indirect and direct heating are often combined to advantage by using the former for the more import- ant rooms, where ventilation is desired, and the latter for rooms more remote or where heat only is required. Another advantage is the large ratio between the radiating sur- face and grate-area, as compared with a furnace ; this results in a large volume of air being warmed to a moderate temperature instead of a smaller quantity being heated to a much higher temperature, thus giving a more agreeable quality to the air and rendering it less dry. Indirect steam is adapted to all the buildings mentioned in con- nection with furnace heating, and may be used to much better advan- tage in those of large size. This applies especially to cases where more than one furnace is necessary; for, with steam heat, a single boiler, or a battery of boilers, may be made to supply heat for a build- HEATING AND VENTILATION ing of any size, or for a group of several buildings, if desired, and is much easier to care for than several furnaces widely scattered. Direct-Indirect Radiators. These radiators are placed in the room the same as the ordinary direct type. The construction is such that when the sections are in place, small flues are formed between them; and air, being admitted through an opening in the outside wall, passes upward through them and becomes heated before entering the' room. A switch damper is placed in the casing at the base of the radiator, so that air may be taken from the room itself instead of from out of doors, if so desired. Radiators of this kind are not used to any great extent, as there is likely to be more or less leakage of cold air into the room around the base. If ventilation is required, it is better to use the regular form of indirect heater with flue and register, if possible. It is sometimes desirable to partially ventilate an isolated room where it would be impossible to run a flue, and in cases of this kind the direct-indirect form is often useful. Direct Hot Water. Hot water is especially adapted to the warm- ing of dwellings and greenhouses, owing to the ease with which the temperature can be regulated. When steam is used, the radiators are always at practically the same temperature, while with hot water the temperature can be varied at will. A system for hot-water heating costs more to install than one for steam, as the radiators must be larger and the pipes more carefully run. On the other hand, the cost of operating is somewhat less, because the water need be carried only at a temperature sufficiently high to warm the rooms properly in mild weather, while with steam the building is likely to become overheated, and more or less heat wasted through open doors and windows. A comparison of the relative costs of installing and operating hot- air, steam, and hot-water systems, is given in Table I. TABLE I Relative Cost of Heating Systems . HOT AIR STEAM HOT WATEH Relative cost of apparatus 9 13 15 Relative cost, adding repairs and fuel for five years 29 i 29| 27 Relative cost, adding repairs and fuel for fifteen years 81 63 52 HEATING AND VENTILATION One disadvantage in the use of hot water is the danger from freezing when radiators are shut off in unused rooms. This makes it necessary in very cold weather to have all parts of the system turned on sufficiently to produce a circulation, even if very slow. This is sometimes accomplished by drilling a very small hole (about J inch) in the valve-seat, to that when closed there will still be a very slow circulation through the radiator, thus preventing the'temperature of the water from reaching the freezing point. Indirect Hot Water. This is used under the same conditions as indirect steam, but more especially in the case of dwellings and hospi- tals. When applied to other and larger buildings, it is customary to force the water through the mains by means of a pump. Larger heating stacks and supply pipes are required than for steam; but the arrangement and size of air-flues and registers are practically the same, although they are sometimes made slightly larger in special cases, Exhaust Steam. Exhaust steam is used for heating in connection with power plants, as in shops and factories, Or in office buildings which have their own lighting plants. There are two methods of using exhaust steam for heating purposes. One is to carry a back pressure of 2 to 5 pounds on the engines, depending upon the length and size of the pipe mains ; and the other is to use some form of vacuum system attached to the returns or air-valves, which tends to reduce the back pressure rather than to increase it. Where the first method is used and a back pressure carried, either the boiler pressure or the cut-off of the engines must be increased, to keep the mean effective pressure the same and not reduce the horse- power delivered. In general it is more economical to utilize the ex- haust steam for heating. There are instances, however, where the relation between the quantities of steam required for heating and for power are such especially if the engines are run condensing that it is better to throw the exhaust away and heat with live steam. Where the vacuum method is used, these difficulties are avoided ; and for this reason that method is coming into quite common use. If the condensation from the exhaust steam is returned to the boilers, the oil must first be removed ; this is usually accomplished by passing the steam through some form of grease extractor as it leaves the engine. The water of condensation is often passed through a separating tank in addition to this, before it is delivered to the return HEATING AND VENTILATION pumps. It is better, however, to remove a portion of the oil before the steam enters the heating system ; otherwise a coating will be formed upon the inner surfaces of the radiators, which will reduce their efficiency to some extent. Forced Blast. This method of heating, in different forms, is used for the warming of factories, schools, churches, theaters, halls in fact, any large building where good ventilation is desired. The air for warming is drawn or forced through a heater of special design, and discharged by a fan or blower into ducts which lead to registers placed in the rooms to be warmed. The heater is usually made up in sections, so that steam may be admitted to or shut off from any section independently of the others, and the temperature of the air regulated in this manner. Sometimes a by-pass damper is attached, so that part of the air will pass through the heater and part around or over it ; in this way the proportions of cold and heated air may be so adjusted as to give the desired temperature to the air entering the rooms. These forms of regulation are common where a blower is used for warming a single room, as in the case of a church or hall; but where several rooms are warmed, as in a schoolhouse. it is customary to use the main or primary heater at the blower for warming the air to a given temperature (somewhat below that which is actually required), and to supplement this by placing secondary coils or heaters at the bottoms of the flues leading to the different rooms. By means of this arrange- ment, the temperature of each room can be regulated independently of the others. The so-called double-duct system is sometimes employed. In this case, two ducts are carried to each register, one supplying hot air and the other cold or tempered air; and a damper for mixing these in the right proportions is placed in the flue, below the register. Electric Heating. Unless electricity can be produced at a' very low cost, it is not practicable for heating residences or large buildings. The electric heater, however, has quite a wide field of application in heating small offices, bathrooms, electric cars, etc. It is a convenient method of warming isolated rooms on cold mornings, in late spring and early fall, when the regular heating apparatus of the building is not in operation. It has the advantage of being instantly available, and the amount of heat can be regulated at will. Electric heaters are clean, do not vitiate the air, and are easily moved from place to place. HEATING AND VENTILATION PRINCIPLES OF VENTILATION Closely connected with the subject of heating is the problem of maintaining air of a certain standard of purity in the various buildings occupied. ^ The introduction of pure air can be done properly only in con- nection with some system of heating; and no system of heating is complete without a supply of pure air, depending in amount upon the kind of building and the purpose for which it is used. Composition of the Atmosphere. Atmospheric air is not a simple substance but a mechanical mixture. Oxygen and nitrogen; the principal constituents, are present in very nearly the proportion of one part of oxygen to four parts of nitrogen by weight. Carbonic acid gas, the product of all combustion, exists in the proportion of 3 to 5 parts in 10,000 in the open country. Water in the form of vapor, varies greatly with the temperature and with the exposure of the air to open boclies of water. In addition to the above, there are generally present, in variable but exceedingly small quantities, ammonia, sulphuretted hydrogen, sulphuric, sulphurous, .nitric, and nitrous acids, floating organic and inorganic matter, and local impurities. Air also contains ozone, which is a peculiarly active form of oxygen ; and lately another constituent called argon has been discovered. Oxygen is the most important element of the air, so far as both heating and ventilation are concerned. It is the active element in the chemical process of combustion and also in the somewhat similar process which takes place in the respiration of human beings. Taken into the lungs, it acts upon the excess of carbon in the blood, and pos- sibly upon other ingredients, forming chemical compounds which are thrown off in the act of respiration or breathing. Nitrogen. The principal bulk of the atmosphere is nitrogen, which exists uniformly diffused with oxygen and carbonic acid gas. This element is practically inert in all processes of combustion or respiration. It is not affected in composition, either by passing through a furnace during combustion or through the lungs in the process of respiration. Its action is to render the oxygen less active, and to absorb some part of the heat produced by the process of oxidation. Carbonic acid gas is of itself only a neutral constituent of the atmosphere, like nitrogen ; and contrary to the general impression its presence in moderately large quantities (if uncombined with other HEATING AND VENTILATION substances) is neither disagreeable nor especially harmful. Its presence, however, in air provided for respiration, decreases the readi- ness with which the carbon of the blood unites with the oxygen of the air; and therefore, when present in sufficient quantity, it may cause indirectly, not only serious, but fatal results. The real harm of a vitiated atmosphere, however, is caused by the other constituent gases and by the minute organisms which are produced in the process of respiration. It is known that these other impurities exist in fixed proportion to the amount of carbonic acid present in an atmosphere vitiated by respiration. Therefore, as the relative proportion of carbonic acid can easily be determined by experiment, the fixing of a standard limit of the amount in which it may be allowed, also limits the amounts of other impurities which are found in combination with it. When carbonic acid is present in excess of 10 parts in 10,000 parts of air, a feeling of weariness and stuffiness, generally accompanied by a headache, will be experienced; while with even 8 parts in 10,000 parts a room would be considered close. For general considerations of ventilation, the limit should be placed at 6 to 7 parts in 10,000, thus allowing an increase of 2 to 3 parts over that present in outdoor air, which may be considered to contain four parts in 10,000 under ordi- nary conditions. Analysis of Air. An accurate qualitative and quantitative analysis of air samples can be made only by an experienced chemist. There are, however, several approximate methods for determining the amount of carbonic acid present, which are sufficiently exact for practical purposes. Among these the following is one of the simplest : The necessary apparatus consists of six clean, dry, and tightly corked bottles, containing respectively 100, 200, 250, 300, 350, and 400 cubic centimeters, a glass tube containing exactly 15 cubic centimeters to a given mark, and a bottle of perfectly clear, fresh limewater. The bottles should be filled with the air to be examined by means of a hand- ball syringe. Add to the smallest bottle 15 cubic centimeters of the limewater, put in the cork, and shake well. If the limewater has a milky appearance, the amount of carbonic acid will be at least 16 parts in 10,000. If the contents of the bottle remain clear, treat the bottle of 200 cubic centimeters in the same manner; a milky appear- ance or turbidity in this would indicate 12 parts in 10,000. In a similar manner, turbidity in the 250 cubic centimeter bottle indicates HEATING AND VENTILATION 9 10 parts in 10,000; in the 300, 8 parts; in the 350, 7 parts; and in the 400, less than 6 parts. The ability to conduct more accurate analyses can be attained only by special study and a knowledge of chemical properties and of methods of investigation. Another method similar to the above, makes use of a glass cylinder containing a given quantity of limewater and provided with a piston. A sample of the air to be tested is drawn into the cylinder by an upward movement of the piston. The cylinder is then thoroughly shaken, and if the limewater shows a milky appearance, it indicates a certain proportion of carbonic acid in the air. If the limewater remains clear, the air is forced out, and another cylinder full drawn in, the operation being repeated until the limewater becomes milky. The size of the cylinder and the quantity of limewater are so propor- tioned that a change in color at the first, second, third, etc., cylinder full of air indicafes different proportions of carbonic acid. This test is really the same in principle as the one previously described; but the apparatus used is in more convenient form. Air Required for Ventilation. The amount of air required to maintain any given standard of purity can very easily be determined, provided we know the amount of carbonic acid given off in the process of respiration. It has been found by experiment that the average production of carbonic acid by an adult at rest is about .6 cubic foot per hour. If we assume the proportion of this gas as 4 parts in 10,000 in the external air, and are to allow 6 parts in 10,000 in an occupied room, the gain will be 2 parts in 10,000; or, in other words, there will 2 be TTTTT = .0002 cubic foot of carbonic acid mixed with each cubic foot of fresh air entering the room. Therefore, if one person gives off .6 cubic foot of carbonic acid per hour, it will require .6 -f- .0002 = 3,000 cubic feet of air per hour per person to keep the air in the room at the standard of purity assumed that is, 6 parts of carbonic acid in 10,000 of air. Table II has been computed in this manner, and shows the amount of air which must be introduced for each person in order to maintain various standards of purity. While this table gives the theoretical quantities of air required for different standards of purity, and may be used as a guide, it will be better in actual practice to use quantities which experience has shown 10 HEATING AND VENTILATION to give good results in different types of buildings. In auditoriums where the cubic space per individual is large, and in which the atmos- phere is thoroughly fresh before the rooms are occupied, and^the occupancy is of only two or three hours' duration, the air-supply may be reduced somewhat from the figures given below. TABLE II Quantity of Air Required per Person STANDARD PARTS OP CARBONIC ACID IN 10,000 OF AIR CUBIC FEET OP AIR REQUIRED PER PERSON IN ROOM Per Minute Per Hour 5 100 6,000 6 50 3,000 7 33 2,000 8 25 1,500 9 20 1,200 10 16 1,000 Table III represents good modern practice and may be used with satisfactory results : TABLE III Air Required for Ventilation of Various Classes of Buildings AIR-SUPPLY PER OCCUPANT FOR CUBIC FEET PER MINUTE CUBIC FEET PER HOUR Hospitals High Schools Grammar Schools Theaters and Assembly Halls Churches 80 to 100 50 40 25 20 4, 800 to 6, 000 3,000 2,400 1,500 1,200 When possible, the air-supply to any given room should be based upon the number of occupants. It sometimes happens, however, that this information is not available, or the character of the room is such that the number of persons occupying it may vary, as in the case of public waiting rooms, toilet rooms, etc. In instances of this kind, the requireH air-volume may be based upon the number of changes per hour. In using this method, various considerations must be taken into account, such as the use of the room and its condition as to crowd- ing, character of occupants, etc. In general, the following will be found satisfactory for average conditions : HEATING AND VENTILATION 11 TABLE IV Number of Changes of Air Required in Various Rooms USE OF ROOM CHANGES op A.IR PER HOUR Public Waiting Room *" 4t o5 Public Toilets 5 6 Coat and Locker Rooms 4 5 Museums 3 4 Offices, Public 4 5 Offices, Private 3 4 Public Dining Rooms 4 5 Living Rooms* 3 4 Libraries, Public 4 5 Libraries, Private 3 4 Force for Moving Air. Air is moved for ventilating purposes in two ways: (1) by expansion due to heating; (2) by mechanical means. The effect of heat on the air is to increase its volume and therefore lessen its density or weight, so that it tends to rise and is replaced by the colder air below. The available force for moving air obtained in this way is very small, and is quite likely to be overcome by wind or external causes. It will be found in general that the heat used for producing Velocity in this manner, when transformed into work in the steam engine, is greatly in excess of that required to pro- duce the same effect by the use of a fan. Ventilation by mechanical means is performed either by pressure or by suction. The for- mer is used for delivering fresh air into a building, and the latter for removing the foul air from it. By both processes the air is moved Fig. 1. Common Form of Anemometer, for . . , , . Measuring Velocity of Air-Currents. without change in temperature, and the force for moving must be sufficient to overcome the effects of wind or changes in outside temperature. Some form of fan is used for this purpose. Measurements of Velocity. The velocity of air in ventilating ducts and flues is measured directly by an instrument called an ane- mometer. A common form of this instrument is shown in Fig. 1. It consists of a series of flat vanes attached to an axis, and a series of dials. 12 HEATING AND VENTILATION The revolution of the axis causes motion of the hands in proportion to the velocity of the air, and the result can be read directly from the dials for any given period. For approximate results the anemometer may be slowly moved across the opening in either vertical or horizontal parallel lines,, so that the readings will be made up of velocities taken from all parts of the opening. For more accurate work, the opening should be divided into a number of squares by means of small twine, and readings taken at the center of each. The mean of these readings will give the average velocity of the air through the entire opening. AIR DISTRIBUTION The location of the air inlet to a room depends upon the size of the room and the purpose for which it is used. In the case of living rooms in dwelling-houses, the registers are placed either in the floor or in the wall near the floor; this brings the warm air in at the coldest part of the room and gives an opportunity for warming or drying the feet if desired. In the case of schoolrooms, where large volumes of warm air at moderate temperatures are required, it is best to discharge it through openings in the wall at a height of 7 or 8 feet from the floor ; this gives a more even distribution, as the warmer air tends to rise and hence spreads uniformly under the ceiling; it then gradually displaces other air, and the room becomes filled with pure air without sensible currents or drafts. The cooler air sinks to the bottom of the room, and can be taken off through ventilating registers placed near the floor. The relative positions of the inlet and outlet are often governed to some extent by the building construction ; but, if possible, they should both be located in the same side of the room. Figs. 2, 3, and 4 show common arrangements. The vent outlet should always, if possible, be placed in an inside wall; otherwise it will become chilled and the air-flow through it will become sluggish. In theaters and churches which are closely packed, the air should enter at or near the floor, in finely-divided streams ; and the discharge ventilation should be through openings in the ceiling. The reason for this is the large amount of animal heat given off from the bodies of the audience ; this causes the air to become still further heated after entering the room, and the tendency is to rise continuously HEATING AND VENTILATION 13 from floor to ceiling, thus carrying away all impurities from respiration as fast as they are given off. All audience halls in which the occupants are closely seated should be treated in the same manner, when possible. This, however, can- *not always be done, afs the seats are often made removable so that the l OUTSIDE WALL OUTSIDE WALL OUTSIDE WALL Fig. 2. Fig. 3. Fig. 4. Diagrams Showing Relative Positions of Air Inlets and Outlets as Commonly Arranged. floor can be used for other purposes. In cases of this kind, part of the air may be introduced through floor registers placed along the outer aisles, and the remainder by means of wall inlets the same as for school- rooms. The discharge ventilation should be partly through registers near the floor, supplemented by ample ceiling vents for use when the hall is crowded or the outside temperature high. The matter of air-velocities, size of flues, etc., will be taken up under the head of "Indirect Heating." HEAT LOSS FROM BUILDINGS A British Thermal Unit, or B. T. U., has been defined as the amount of heat required to raise the temperature of one pound of water one degree F. This measure of heat enters into many of the calculations involved in the solving of problems in heating and ventila- tion, and one should familiarize himself with the exact meaning of the term. Causes of Heat Loss. The heat loss from a building is due to the following causes: (1) radiation and conduction of heat through walls and windows; (2) leakage of warm air around doors and win- dows and through the walls themselves; and (3) heat required to warm the air for ventilation. Loss through Walls and Windows. The loss of heat through the walls of a building depends upon the material used in construction 14 HEATING AND VENTILATION TABLE V Heat Losses in B. T. U. per Square Foot of Surface per Hour- Southern Exposure MATERIAL DIFFERENCE BETWEEN INSIDE AND OUT- SIDE TEMPERATURES 10 5 4 3 2.8 2.5 2 1.5 12 8 11 7 4 3 6 5 2 1.5 1 3 20 30 40 18 13 10 9 8 7 6 49 32 42 28 16 11 24 20 9 6 4 10 50 60 27 20 16 14 12 11 10 73 48 63 42 24 17 36 30 13 9 6 16 70 31 23 19 16 14 13 11 85 56 73 48 28 20 42 35 15 10 7 19 80 90 40 30 24 20 18 16 15 110 70 94 62 36 25 54 45 20 13 9 24 100 45 33 27 23 20 18 16 122 78 104 70 40 28 60 50 22 15 10 27 8-in Brick Wall 9 7 5 4.5 4 3.5 3 24 16 21 14 8 5 12 10 4 3 2 5 13 10 8 7 6 5 4.5 36 24 31 20 12 8 18 15 6.5 4.5 3 8 22 16 13 11 10 9 8 60 40 52 35 20 14 30 25 11 f t 13 36 26 22 18 16 14 13 93 62 - 84 56 32 23 48 40 18 12 8 22 12-in Brick Wall 16-in Brick Wall 20-in Brick Wall 24-in Brick Wall 28-in Brick Wall 32-in Brick Wall Single \Vindow Double Window Single Skylight Double Skylight 1-in \Voodcn Door 2-in \Vooden Door 2-in Solid Plaster Partition 3-in Solid Plaster Partition Concrete Floor on Brick Arch .... \Vood Floor on Brick ./Trch Double Wood Floor Walls of Ordinary Wooden Dwellings For solid stone watts, multiply the figures for brick of the same thickness by 1.7. Where rooms have a cold attic above or cellar beneath, multiply the heat loss through walls and windows by 1 . 1 . Correction for Leakage. The figures given in the above table apply only to the most thorough construction. For the average well-built house, the results should be increased about 10 per cent; for fairly good construction, 20 per cent; and for poor construction, 30 per cent. Table V applies only to a southern exposure; for other exposures multi- ply the heat loss given in Table V by the factors given in Table VI. of the wall, the thickness, the number of layers, and the difference between the inside and outside temperatures. The exact amount of heat lost in this way is very difficult to determine theoretically, hence we depend principally on the results of experiments. Loss by Air-Leakage. The leakage of air from a room varies from one to. two or more changes of the entire contents per hour, depending upon the construction, opening of doors, etc. It is com- mon practice to allow for one change per hour in well-constructed buildings where two walls of the room have an outside exposure. As the amount of leakage depends upon the extent of exposed wall and window surface, the simplest way of providing for this is to increase HEATING AND VENTILATION 15 TABLE VI Factors lor Calculating Heat Loss for Other than Southern Exposures EXPOSURE FACTOR N. ^ .32 E. .12 S. .0 w. .20 N.E. .22 N. W. .26 8.E. .06 S.W. .10 N., E., S., and W., or total exposure 1.16 the total loss through walls and windows by a factor depending upon the tightness of the building construction. Authorities differ con- siderably in the factors given for heat losses, and there are various methods for computing the same. The figures given in Table V have been used extensively in actual practice, and have been found to give good results when used with judgment. The table gives the heat losses through different thicknesses of walls, doors, windows, etc., in B. T. U., per square foot of surface per hour, for varying differences in inside and outside temperatures. In computing the heat loss through walls, only those exposed to the outside air are considered. In order to make the use of the table clear, we shall give a num- ber of examples illustrating its use: Example 1. Assuming an inside temperature of 70, what will be the heat loss from a room having an exposed wall surface of 200 square feet and a glass surface of 50 square feet, when the outside temperature is zero? The wall is of brick, 16 inches in thickness, and has a southern exposure; the win- dows are single; and the construction is of the best, so that no account need be taken, of leakage We find from Table V, that the factor for a 16-inch brick wall with a difference in temperature of 70 is 19, and that for glass (single window) under the same condition is 85; therefore, Loss through walls = 200 X 19 = = 3,800 Loss through windows = 50 X 85 = = 4,250 Total loss per hour - 8,050 B. T. U. Example 2. A room 15 ft. square and 10 ft. high has two exposed walls, one toward the north, and the other toward the west. There are 4 windows, each 3 feet by 6 feet in size. The two in the north wall are double, while the 16 HEATING AND VENTILATION other two are single. The walls are of brick, 20 inches in thickness. With an inside temperature of 70, what will be the heat loss per hour when it is 10 below zero? Total exposed surface = 15 X 10 X 2 - 300 Glass surface =,3X6X4= 72 Net wall surface = 228 Difference between inside and outside temperature 80. Factor for 20-inch brick wall is 18. Factor for single window is 93. Factor for double window is 62. The heat losses are as follows : Wall, 228 X 18 = 4,104 Single windows, 36 X 93 = 3,348 Double windows, 36 X 62 = 2,232 9,684 B.T.U. As one side is toward the north, and the other toward the west, the actual exposure is N. W. Looking in Table VI, we find the correction factor for this exposure to be 1.26; therefore the total heat loss is 9,684 X 1.26 = 12,201.84 B.T.U. Example 3. A dwelling-house of fair wooden construction measures 160 ft. around the outside; it has 2 stories, each 8 ft. in height; the windows are single, and the glass surface amounts to one-fifth the total exposure; the attic and cellar are unwarmed. If 8,000 B. T. U. are utilized from each pound of coal burned in the furnace, how many pounds will be required per hour to maintain a temperature of 70 when it is 20 above zero outside? Total exposure = 160 X 16 = 2,560 Glass surface = 2,560 -*- 5 = 512 Net wall =2,048 Temperature difference = 70 - 20 = 50 Wall 2,048 X 13 = 26,624 Glass 512 X 60 = 30,720 57,344 B.T.U. As the building is exposed on all sides, the factor for exposure will be the average of those for N., E., S., and W., or (1.32 + 1.12 + 1.0 + 1.20) -5- 4 = 1.16 The house has a cold cellar and attic, so we must increase the heat loss HEATING AND VENTILATION 17 10 per cent for each of the first two conditions, and 20 per cent for the last. Making these corrections we have: 57,344 X 1.16 X 1.10 X 1.10 X 1.20 = 96,338B.T.U. If one pound of coal furnishes 8,000 B. T. IL, then 96,338 -T- 8,000 = 12 pounds of coal -per hour required to warm the building to 70 under the conditions stated. Approximate Method. For dwelling-houses of the average con- struction, the following simple method for calculating the heat loss may be used. Multiply the total exposed surface by 45, which will give the heat loss in B. T. U. per hour for an inside temperature of 70 in zero weather. This factor is obtained in the following manner : Assume the glass surface to be one-sixth the total exposure, which is an average propor- tion. Then each square foot of exposed surface consists one-sixth of glass and five-sixths of wall, and the heat loss for 70 difference in temperature would be as follows : Wall 4- X 19 = 15.8 6 Glass X 85 - 14.1 6 29.9 Increasing this 20 per cent for leakage, 16 per cent for exposure, and 10 per cent for cold ceilings, we have : 29.9 X 1.20 X 1.16 X 1.10 = 45. The loss through floors is considered as being offset by including the kitchen walls of a dwelling-house, which are warmed by the range, and which would not otherwise be included if computing the size of a furnace or boiler for heating. If the heat loss is required for outside temperatures other than zero, multiply by 50 for 10 degrees below, and by 40 for 10 degrees above zero. This method is convenient for approximations in the case of dwelling-houses; but the more exact method should be used for other types of buildings, and in all cases for computing the heating surface for separate rooms. When calculating the heat loss from isolated rooms, the cold inside walls as well as the outside must be considered. The loss through a wall next to a cold attic or other unwarmed space may in general be taken as about two-thirds that of an outside wall. 18 HEATING AND VENTILATION Heat Loss by Ventilation. One B. T. U. will raise the tempera- ture of 1 cubic foot of air 55 degrees at average temperatures and pressures, or will raise 55 cubic feet 1 degree, so that the heat required for the ventilation of any room can be found by the following formula : Cu. ft. of air per hour X Number of degrees rise = fi T ^ requ ired oo To compute the heat loss for any given room which is to be ventilated, first find the loss through walls and windows, and correct for exposure and leakage; then compute the amount required for ventilation as above, and take the sum of the two. An inside tem- perature of 70 is always assumed unless otherwise stated. Examples. What quantity of heat will be required to warm 100,000 cubic feet of air to 70 for ventilating purposes when the outside temperature is 10 below zero? 100,000 X 80 -T- 55 = 145,454 B. T. U. How many B. T. U. will be required per hour for the ventilation of a church seating 500 people, in zero weather? Referring to Table III, we find that the total air required per hour is 1,200 X 500 = 600,000 cu. ft.; therefore 600,000 X 70 -*- 55 = 763,636 B. T. U. . Rise in Temperature . . The factor - is approximately 1.1 tor 60 , 55 1.3 for 70, and 1.5 for 80. Assuming a temperature of 70 for the entering air, we may multiply the air-volume supplied for ventilation by 1.1 for an outside temperature of 10 above 0, by 1.3 for zero, and by 1.5 for 10 below zero which covers the conditions most commonly met with in practice. EXAMPLES FOR PRACTICE 1. A room in a grammar school 28 ft. by 32 ft. and 12 feet high is to accommodate 50 pupils. The walls are of brick 16 inches in thick- ness; and there are 6 single windows in the room, each 3 ft. by 6 ft.; there are warm rooms above and below; the exposure is S. E. How many B. T. U. will be required per hour for warming the room, and how many for ventilation, in zero weather, assuming the building to be of average construction? ANS. 24,261 + for warming; 152,727 + for ventilation. 2. A stone church seating 400 people has walls 20 inches in thickness. It has a wall exposure of 5,000 square feet, a glass expos- HEATING AND VENTILATION 19 ure (single windows) of 600 square feet, and a roof exposure of 7,000 square feet; the roof is of 2-inch pine plank, and the factor for heat loss may be taken the same as for a 2-inch wooden door. The floor is of wood on brick arches, and has an area of 4,000 square feet. The building is exposed on all sides, and is of first-class construction. What will be the heat required per hour for both warming and ventila- tion when the outside temperature is 20 above zero? ANS. 296,380 for warming; 436,363 + for ventilation. 3. A dwelling-house of average wooden construction measures 200 feet around the outside, and has 3 stories, each 9 feet high. Compute the heat loss by the approximate method when the tem- perature is 10 below zero. ANS. 270,000 B. T. U. per hour. FURNACE HEATING In construction, a furnace is a large stove with a combustion chamber of ample size over the fire, the whole being inclosed in a casing of sheet iron or brick. The bottom of the casing is provided with a cold-air inlet, and at the top are pipes which connect with registers placed in the various rooms to be heated. Cold, fresh air is brought from out of doors through a pipe or duct called the cold-air box; this air enters the space between the casing and the furnace near the bottom, and, in passing over the hot surfaces of the fire-pot and combustion, chamber, becomes heated. It then rises through the warm-air pipes at the top of the casing, and is discharged through the registers into the rooms above. As the warm air is taken from the top of the furnace, cold air flows in through the cold-air box to take its place. The air for heating the rooms does not enter the combustion chamber. Fig. 5 shows the general arrangement of a furnace with its con- necting pipes. The cold-air inlet is seen at the bottom, and the hot-air pipes at the -top; these are all provided with dampers for shutting off or regulating the amount of air flowing through them. The feed or fire door is shown at the front, and the ash door beneath it; a water-pan is placed inside the casing, and furnishes moisture to the warm air before passing into the rooms; water is either poured into the pan through an opening in the front, provided for this purpose, or is supplied auto- matically through a pipe. 20 HEATING AND VENTILATION The fire is regulated by means of a draft slide in the ash door, and a cold-air or regulating damper placed in the smoke-pipe. Clean-out doors are placed at different points in the casing for the removal of ashes and soot. Furnaces are made either of cast iron, or of wrought- iron plates riveted together and provided with brick-lined firepots. Types of Furnaces. Furnaces may be divided into two general HEATING AND VENTILATION 21 types known as direct-draft and indirect-draft. Fig. 6 shows a com- mon form of direct-draft furnace with a brick setting; the better class have a radiator, generally placed at the top, through which the gases pass before reaching the smoke-pipe. They have but one damper, usually combined witK^a cold-air check. Many of the cheaper direct- Fig. 6. A Common Type of Direct-Draft Furnace in Brick Setting. Cast-Iron Radiator at Top. draft furnaces have no radiator at all, the gases passing directly into the smoke-pipe and carrying away much heat that should be utilized. The furnace shown in Fig. 6 is made of cast iron and has a large radiator at the top; the smoke connection is shown at the rear. Fig. 7 represents another form of direct-draft furnace. In this case the radiator is made of sheet-steel plates riveted together, and the outer casing is of heavy galvanized iron instead of brick. In the ordinary indirect-draft type of furnace (see Fig. 8), the gases pass downward through flues to a radiator located near the base, 22 HEATING AND VENTILATION thence upward through another flue to the smoke-pipe. In addition to the damper in the smoke-pipe, a direct-draft damper is required to give direct connection with the funnel when coal is first put on, to facilitate the escape of gas to the chimney. When the chimney draft Fig. 7. Direct- Draft Furnace with Galvanized-Iron Casing. Radiator (at top) Made of Riveted Steel Plates. is weak, trouble from gas is more likely to be experienced with fur- naces of this type than with those having a direct draft. Grates. No part of a furnace is of more importance than the grates. The plain grate rotating about a center pin was for a long time the one most commonly used. These grates were usually pro- vided with a clinker door for removing any refuse too large to pass between the grate bars. The action of such grates tends to leave a HEATING AND VENTILATION 23 cone of ashes in the center of the fire causing it to burn more freely around the edges. A better form of grate is the revolving triangular pattern, which is now used in many of the leading furnaces. It con- sists of a series of triangular bars having teeth. The bars are con- nected by gears, and are turned by means of a detachable lever. If Indirect-Draft Type of Furnace. Gases Pass Downward to Radiator at Bottom, Thence Upward to Smoke-Pipe. properly used, this grate will cut a slice of ashes and clinkers from under the entire fire with little, if any loss of unccnsumed coal. The Firepot. Firepots are generally made of cast iron or of steel plate lined with firebrick. The depth ranges from about 12 to 18 inches. In cast-iron furnaces of the better class, the firepot is made very heavy, to insure durability and to render it less likely to become red-hot. The firepot is sometimes made in two pieces, to reduce the 24 HEATING AND VENTILATION liability to cracking. The heating surface is sometimes increased by corrugations, pins, or ribs. A firebrick lining is necessary in a wrought-iron or steel furnace to protect the thin shell from the intense heat of the fire. Since brick- lined firepots are much less effective than cast-iron in transmitting heat, such furnaces depend to a great extent for their efficiency on the heating surface in the dome and radiator; and this, as a rule, is much greater than in those of cast iron. Cast-iron furnaces have "the advantage when coal is first put on (and the drop flues and radiator are cut out by the direct damper) of still giving off heat from the firepot, while in the case of brick linings very little heat is given off in this way, and the rooms are likely to become somewhat cooled before the fresh coal becomes thoroughly ignited. Combustion Chamber. The body of the furnace above the fire- pot, commonly called the dome or feed section, provides a combustion chamber. This chamber should be of sufficient size to permit the gases to become thoroughly mixed with the air passing ap through the fire or entering through openings provided for the purpose in the feed door. In a well-designed furnace, this space should be somewhat larger than the firepot. Radiator. The radiator, so called, with which all furnaces of the better class are provided, acts as a sort of reservoir in which the gases are kept in contact with the air passing over the furnace until they have parted with a considerable portion of their heat. Radiators are built of cast iron, of steel plate, or of a combination of the two. The former is more durable and can be made with fewer joints, but owing to the difficulty of casting radiators of large size, steel plate is commonly used for the sides. The effectiveness of a radiator depends on its form, its heating surface, and the difference between the temperature of the gases and the surrounding air. Owing to the accumulation of soot, the bottom surface becomes practically worthless after the furnace has been in use a short time; surfaces, to be effective, must therefore be self- cleaning. If the radiator is placed near the bottom of the furnace the gases are surrounded by air at the lowest temperature, which renders the radiator more effective for a given size than if placed near the top and HEATING AND VENTILATION 25 surrounded by warm air. On the other hand, the cold air has a ten- dency to condense the gases, and the acids thus formed are likely to corrode the iron. Heating Surface. The different heating surfaces may be de- scribed as follows: I^irepot surface; surfaces acted upon by direct rays of heat from the fire, such as the dome or combustion chamber; gas- or smoke-heated surfaces, such as flues or radiators; and ex- tended surfaces, such as pins or ribs. Surfaces unlike in character and location, -vary greatly in heating power, so that, in making com- parisons of different furnaces, we must know the kind, form, and location of the heating surfaces, as well as the area. In some furnaces having an unusually large amount of surface, it will be found on inspection that a large part would soon become practically useless from the accumulation of soot. In others a large portion of the surface is lined with firebrick, or is so situated that the air-currents are not likely to strike it. The ratio of grate to heating surface varies somewhat according to the size of furnace. It may be taken as 1 to 25 in the smaller sizes, and 1 to 15 in the larger. Efficiency. One of the first items to be determined in esti- mating the heating capacity of a furnace, is its efficiency that is, the proportion of the heat in the coal that may be utilized for warming. The efficiency depends chiefly on the area of the heating surface as compared with the grate, on its character and arrangement, and on the rate of combustion. The usual proportions between grate and heating surface have been stated. The rate of combustion required to maintain a temperature of 70 in the house, depends, of course, on the outside temperature. In very cold weather a rate of 4 to 5 pounds of coal per square foot of grate per hour must be main- tained. One pound of good anthracite coal will give off about 13,000 B. T. U., and a good furnace should utilize 70 per cent of this heat. The efficiency of an ordinary furnace is often much less, sometimes as low as 50 per cent. In estimating the required size of a first-class furnace with good chimney draft, we may safely count upon a maximum combustion of 5 pounds of coal per square foot of grate per hour, and may assume that 8,000 B. T. U. will be utilized for warming purposes from each 26 HEATING AND VENTILATION pound burned. This quantity corresponds to an efficiency of 60 per cent. Heating Capacity. Having determined the heat loss from a building by the methods previously given, it is a simple matter to compute the size of grate necessary to burn a sufficient quantity of coal to furnish the amount of heat required for warming. In computing the size of furnace, it is customary to consider the whole house as a single room, with four outside walls and a cold attic. The heat losses by conduction and leakage are computed, and in- creased 10 per cent for the cold attic, and 16 per cent for exposure. The heat delivered to the various rooms may be considered as being made up of two parts first, that required to warm the outside air up to 70 (the temperature of the rooms); and second, the quantity which must be added to this to offset the loss by conduction and leak- age. Air is usually delivered through the registers at a temperature of 120, with zero conditions outside, in the best class of residence work; so that of the heat given to the entering air may be con- 50 sidered as making up the first part, mentioned above, leaving available for purely heating purposes. From this it is evident that 50 the heat supplied to the entering air must be equal to 1 -=- --- =2.4 times that required to offset the loss by conduction and leakage. Example. The loss through the walls and windows of a building is found to be 80,000 B. T. U. per hour in zero weather. What will be the size of furnace required to maintain an inside temperature of 70 degrees? From the above, we have the total heat required, equal to 80,000 X 2.4 - 192,000 B. T. U. per hour. If we assume that 8,000 B. T. U. are utilized per pound of coal, then 192,000 + 8,000 = 24 pounds of coal required per hour; and if 5 pounds can be burned on each 24 square foot of grate per hour, then = 4.8 square feet required. o A grate 30 inches in diameter has an area of 4.9 square feet, and is the size we should use. When the outside temperature is taken as 10 below zero, multi- ply by 2.6 instead of 2.4; and multiply by 2.8 for 20 below. Table VII will be found useful in determining the diameter of firepot required. HEATING AND VENTILATION 27 TABLE VII Firepot Dimensions AVERAGE DIAMETER OF GRATE, IN INCHES AREA IN SQUARE FEET 18 > 1.77 20 2.18 22 2.64 24 3.14 26 3.69 28 4.27 30 4.91 32 5.58 EXAMPLES FOR PRACTICE 1. A brick apartment house is 20 feet wide, and has 4 stories, each being 10 feet in height. The house is one of a block, and is exposed only at the front and rear. The walls are 16 inches thick, and the block is so sheltered that no correction need be made for exposure. Single windows make up -J- the total exposed surface. Figure for cold attic but warm basement. What area of grate surface will be required for a furnace to keep the house at a temperature of 70 when it is 10 below zero outside? ANS. 3.5 square feet. 2. A house having a furnace with a firepot 30 inches in diameter, is not sufficiently warmed, and it is decided to add a second furnace to be used in connection with the one already in. The heat loss from the building is found by computation to be 133,600 B. T. U. per hour, in zero weather. What diameter of firepot will be required for the extra furnace? ANS. 24 inches. Location of Furnace. A furnace should be so placed that the warm-air pipes will be of nearly the same length. The air travels most readily through pipes leading toward the sheltered side of the house and to the upper rooms. Therefore pipes leading toward the north or west, or to rooms on the first floor, should be favored in regard to length and size. The furnace should be placed somewhat to the north or west of the center of the house, or toward the points of compass from which the prevailing winds blow. Smoke=Pipes. Furnace smoke-pipes range in size from about 6 inches in the smaller sizes to 8 or 9 inches in the larger ones. They are generally made of galvanized iron of No. 24 gauge or heavier. The pipe should be carried to the chimney as directly as possible, 28 HEATING AND VENTILATION avoiding bends which increase the resistance and diminish the draft. Where a smoke-pipe passes through a partition, it should be pro- tected by a soapstone or double-perforated metal collar having a diameter at least 8 inches greater than that of the pipe. The top of the smoke-pipe should not be placed within 8 inches of unprotected beams, nor less than 6 inches under beams protected by asbestos or plaster with a metal shield beneath. A collar to make tight con- nection with the chimney should be riveted to the pipe about 5 inches from the end, to prevent the pipe being pushed too far into the flue. Where the pipe is of unusual length, it is well to cover it to prevent loss of heat and the condensation of smoke. Chimney Flues. Chimney flues, if built of brick, should have walls 8 inches in thickness, unless terra-cotta linings are used, when only 4 inches of brickwork is required. Except in small houses where an 8 by 8-inch flue may be used, the nominal size of the smoke flue should be at least 8 by 12-inches, to allow for contractions or off- sets. A clean-out door should be placed at the bottom of the flue, for removing ashes and soot. A square flue cannot be reckoned at its full area, as the corners are of little value. To avoid down drafts, the top of the chimney must be carried above the highest point of the roof unless provided with a suitable hood or top. Cold=Air Box. The cold-air box should be large enough to supply a volume of air sufficient to fill all the hot-air pipes at the same time. If the supply is too small, the distribution is sure to be unequal, and the cellar will become overheated from lack of air to carry away the heat generated. If a box is made too small, or is throttled down so that the volume of air entering the furnace is not large enough to fill all the pipes, it will be found that those leading to the less exposed side of the house or to the upper rooms will take the entire supply, and that additional air to supply the deficiency will be drawn down through registers in rooms less favorably situated. It is common practice to make the area of the cold-air box three-fourths the combined area of the hot-air pipes. The inlet should be placed where the prevailing cold winds will blow into it; this is commonly on the north or west side of the house. If it is placed on the side away from the wind, warm air from the furnace is likely to be drawn out through the cold-air box. HEATING AND VENTILATION 29 Whatever may be the location of the entrance to the cold-air box, changes in the direction of the wind may take place which will bring the inlet on the wrong side of the house. To prevent the possibility of such changes affecting the action of the furnace, the cold-air box is sometimes extended through the house and left open at both ends, with check-dampers arranged to prevent back-drafts. These checks should be placed some distance from the entrance, to prevent their becoming clogged with snow or sleet. The cold-air box is generally made of matched boards; but galvanized iron is much better; it costs more than wood, but is well worth the extra expense on account of tightness, which keeps the dust and ashes from being drawn into the furnace casing to be discharged through the registers into the rooms above. The cold-air inlet should be covered with galvanized wire netting with a mesh of at least three-eighths of an inch. The frame to which it is attached should not x , Al _ . , FOR RETURNING be smaller than the in- mjL f AIR TRQM ABOVE: side dimensions of the cold-air box. A door to admit air from the cellar to the cold-air box is generally provided. As a rule, air should be taken from this source, only when the house is temporarily unoccupied or during high winds. Return Duct. In some cases it is desirable to return air to the fur- nace from the rooms above, to be reheated. Ducts for this purpose are common in places GOLD AIR /NLET Fig 9. Common Method of Connecting Return Duct to Cold- Air Box. where the winter temperature is frequently below zero. Return ducts when used, should be in addition to the regular cold-air box. Fig. 9 shows a common method of making the connection between the two. By proper adjustment of the swinging damper, the air can be taken either from out of doors or through the register from the room above. The return register is often placed in the hallway of 30 HEATING AND VENTILATION a house, so that it will take the cold air which rushes in when the door is opened and also that which may leak in around it while closed. Check-valves or flaps of light gossamer or woolen cloth should be placed between the cold-air box and the registers to pre- vent back-drafts during winds. The return duct should not be used too freely at the expense of outdoor air, and its use is not recommended except during the night when air is admitted to the sleeping rooms through open windows. Warm=Air Pipes. The required size of the warm-air pipe to any given room, depends on the heat loss from the room and on the volume of warm air required to offset this loss. Each cubic foot of air warmed from zero to 120 degrees brings into a room 2.2 B. T. U. We have already seen that in zero weather, with the air entering the 50 registers at 120 degrees, only rof the heat contained in the air is available for offsetting the losses by radiation and conduction, so that 50 only 2 . 2 X ------- = = . 9" B. T. U. in each cubic foot of entering air can be utilized for warming purposes. Therefore, if we divide the com- puted heat loss in B. T. U. from a room, by .9, it will give the number of cubic feet of air at 120 degrees necessary to warm the room in zero weather. As the outside temperature becomes colder, the quantity of heat brought in per cubic foot 'of air increases; but the proportion avail- able for warming purposes becomes less at nearly the same rate, so TABLE VIII Warm=Air Pipe Dimensions DIAMETER OF PIPE, IN INCHES AREA IN SQUARE INCHES AREA IN SQUARE FEET 6 28 .196 7 38 .267 8 50 .349 9 64 .442 10 79 .545 11 95 .660 12 113 .785 ' 13 133 .922 14 154 1.07 15 177 1.23 16 201 1.40 HEATING AND VENTILATION 31 that for all practical purposes we may use the figure .9 for all usual conditions. In calculating the size of pipe required, we may assume maximum velocities of 260 and 380 feet per minute for rooms on the first and second floors respectively. Knowing the number of cubic feet of air per minute^to be delivered, we can divide it by the velocity, which will give us the required area of the pipe in square feet. Round pipes of tin or galvanized iron are used for this purpose. Table VIII will be found useful in determining the required diameters of pipe in inches. Example. The heat loss from a room on the second floor is 18,000 B. T. U. per hour. What diameter of warm-air pipe will be required? 18,000 -r- .9 = 20,000 = cubic feet of air required per hour. 20,000 -r- 60 = 333 per minute. Assuming a velocity of 380 feet per minute, we have 333 -r- 380 = .87 square foot, which is the area of pipe required. Referring to Table VIII, we find this comes between a 12-inch and a 13-inch pipe, and the larger size would probably be chosen. EXAMPLES FOR PRACTICE 1. A first-floor room has a computed loss of 27,000 B. T. U. per hour when it is 10 below zero. The air for warming is to enter through two pipes of equal size, and at a temperature of 120 degrees. What will be the required diameter of the pipes? ANS. 14 inches. 2. If in the above example the room had been on the second floor, and the air was to be delivered through a single pipe, what diameter would be required? Axs. 16 inches. Since long horizontal runs of pipe increase the resistance and loss of heat, they should not in general be over 12 or 14 feet in length. This applies especially to pipes leading to rooms on the first floor, or to those on the cold side of the house. Pipes of excessive length should be increased in size because of the added resistance. Figs. 10 and 11 show common methods of running the pipes in the basement. The first gives the best results, and should be used where the basement is of sufficient height to allow it. A damper should be placed in each pipe near the furnace, for regulating the flow of air to the different rooms, or for shutting it off entirely when desirecj. 32 HEATING AND VENTILATION While round pipe risers give the best results, it is not always possible to provide a sufficient space for them, and flat or oval pipes are substituted. When vertical pipes must be placed in single par- titions, much better results will be obtained if the studding can be Fig. 10. Fig. 11. Common Methods of Running Hot- Air Pipes in Basement. Method Shown in Fig. 10 is Preferable where Feasible. made 5 or 6 inches deep instead of 4 as is usually done. Flues should never in any case be made less than 3J inches in depth. Each room should be heated by a separate pipe. In some cases, however, it is allowable to run a single riser to heat two unimportant rooms on an upper floor. A clear space of at least | inch should be left between the risers and studs, and the latter should be carefully tinned, and the TABLE IX Dimensions of Oval Pipes DIMENSION OF PlPE AREA IN SQUARE INCHES 6 ovaled to 5 in. 27 7 4 " 31 7 3| " 29 7 6 " 38 8 - 5 " 43 9 4 " 45 9 6 " 57 9 5 " 51 10 3J " 46 11 4 " 58 12 3i " 55 10 6 " 67 11 5 " 67 14 4 " 76 15 3J " 73 12 6" " 85 12 5 " 75 19 4 " 96 20 ' 3i " 100 HEATING AND VENTILATION 33 space between them on both sides covered with tin, asbestos, or wire lath. Table IX gives the capacity of oval pipes. A 6-inch pipe ovaled to 5 means that a 6-inch pipe has been flattened out to a thickness of 5 inches, and colump 2 gives the resulting area. Having determined the size of round pipe required, an equiva- lent oval pipe can be selected from the table to suit the space available. Registers. The registers which control the supply of warm air to the rooms, generally have a net area equal to two-thirds of their gross area. The net area should be from 10 to 20 per cent greater than the area of the pipe connected with it. It is common practice to use registers having the short dimensions equal to, and the long dimensions about one-half greater than, the diameter of the pipe. This would give standard sizes for different diameters of pipe, as listed in Table X. TABLE X Sizes of Registers for Different Sizes of Pipes DIAMETER OF PIPE SIZE OF REGISTER G ii i. 6 X 10 i n. 7 ' 7 X 10 ' 8 ' ( 8 X 12 9 ' t 9 X 14 10 10 X 15 11 11 X 16 12 12 X 17 13 14 X 20 14 14 X 22 15 15 X 22 16 16 X 24 Combination Systems. A combination system for heating by hot air and hot water consists of an ordinary furnace with some form of surface for heating water, placed either in contact with the fire or suspended above it. Fig. 12 shows a common arrangement where part of the heating surface forms a portion of the lining to the firepot and the remainder is above the fire. Care must be taken to proportion properly the work to be done by the air and the water; else one will operate at the expense of the other. One square foot of heating surface in contact with the fire is capable of supplying from 40 to 50 square feet of radiating surface, 34 HEATING AND VENTILATION and one square foot suspended over the fire will supply from 15 to 25 square feet of radiation. The value or efficiency of the heating surface varies so widely in different makes that it is best to state the required conditions to the Fig. 12. Combination Furnace, for Heating by Both Hot Air and Hot Water. manufacturers and have them proportion the surfaces as their experi- ence has found best for their particular type of furnace. Care and Management of Furnaces. The following general rules apply to the management of all hard coal furnaces. The fire should be thoroughly shaken once or twice daily in cold weather. It is well to keep the firepot heaping full at all times. In HEATING AND VENTILATION 35 this way a more even temperature may be maintained, less attention is required, and no more coal is burned than when the pot is only partly filled. In mild weather the mistake is frequently made of carrying a thin fire, which requires frequent attention and is likely to die out. Instead, to diminish the temperature in the house, keep the firepot full and allow ashes x to accumulate on the grate (not under it) by shak- ing less frequently or less vigorously. The ashes will hold the heat and render it an easy matter to maintain and control the fire. When feeding coal on a low fire, open the drafts and neither rake nor shake the fire till the fresh coal becomes ignited. The air supply to the fire is of the greatest importance. An insufficient amount results in incom- plete combustion and a great loss of heat. To secure proper combus- tion, the fire should be controlled principally by means of the ash-pit through the ash-pit door or slide. The smoke-pipe damper should be opened only enough to carry off the gas or smokd and to give the necessary draft. The openings in the feed door act as a check on the fire, and should be kept closed , during cold weather, except just after firing, when with a good draft they may be partly opened to increase the air-supply and promote the proper combustion of the gases. Keep the ash-pit clear to avoid warping or melting the grate. The cold-air box should be kept wide open except during winds or when the fire is low. At such times it may be partly, but never com- pletely closed. Too much stress cannot be laid on the importance of a sufficient air-supply to the furnace. It costs little if any more to maintain a comfortable temperature in the house night and day than to allow the rooms to become so cold during the night that the fire must be forced in the morning to warm them up to a comfortable temperature. In case the warm air fails at times to reach certain rooms, it may be forced into them by temporarily closing the registers in other rooms. The current once established will generally continue after the other registers have been opened. It is best to burn as hard coal as the draft will warrant. Egg size is better than larger coal, since for a given weight small lumps expose more surface and ignite more quickly than larger ones. The furnace and smoke-pipe should be thoroughly deaned once a year. 30 HEATING AND VENTILATION This should be done just after the fire has been allowed to go out in the spring. STEAM BOILERS Types. The boilers used for heating are the same as have already been described for power work. In addition there is the cast-iron sectional boiler, used almost exclusively for dwelling-houses. Tubular Boilers. Tubular boilers are largely used for heating purposes, and are adapted to all classes of buildings except dwelling- houses and the special cases mentioned later, for which sectional boilers are preferable. A boiler horse-power has been defined as the evaporation of 34 J pounds of water from and at a temperature of 212 degrees, and in doing this 33,317 B. T. U. are absorbed, which are again given out when the steam is condensed in the radiators. Hence to find the boiler H. P. required for warming any given building, we have only to compute the heat loss per hour by the methods already given, and divide the result by 33,330. It is more common to divide by the number 33,000, which gives a slightly larger boiler and is on the side of safety. The commercial horse-power of a well-designed boiler is based upon its heating surface; and for the best economy in heating work, it should be so proportioned as to have about 1 square foot heating of surface for each 2 pounds of water to be evaporated from and at 212 degrees F. This gives 34.5 -?- 2 = 17.2 square feet of heating surface per horse-power, which is generally taken as 15 in practice. Makers of tubular boilers commonly rate them on a basis of 12 square feet of heat- ing surface per horse-power. . This is a safe figure under the conditions of power work, where skilled firemen are employed and where more care is taken to keep the heating surfaces free from soot and ashes. For heating plants, however, it is better to rate the boilers upon 15 square feet per horse-power as stated above. There is some difference of opinion as to the proper method of computing the heating surface of tubular boilers. In general, all surface is taken which is exposed to the hot gases on one side and to the water on the other. A safe rule, and the one by which Table XII is computed, is to take J the area of the shell, f of the rear head, less the tube area, and the interior surface of all the tubes. The required amount of grate area, and the proper ratio of heat- HEATING AND VENTILATION 37 ing surface to grate area, vary a good deal, depending on the character of the fuel and on the chimney draft. By assuming the probable rates of combustion and evaporation, we may compute the required grate area for any boiler from the formula : //. P. x 34.5 E XC ' in which S = Total grate area, in square feet; E = Pounds of water evaporated per pound of coal ; C = Pounds of coal burned per square foot of grate per hour. Table XI gives the approximate grate area per H. P. for different rates of evaporation and combustion as computed by the above equation. TABLE XI Orate Area per Horse-Power for Different Rates of Evaporation and Combustion i POUNDS OF COAL BURNED PER SQUARE FOOT OF GRATE PER HOUR POUNDS OF STEAM PER POUND OF COAL 8 Ibs; 10 Ibs. 12 Ibs. Square Feef of Grate Surface per Horse- Power 10 .43 .35 .28 9 .48 .38 .32 8 .54 .43 .36 7 .62 .49 .41 6 .72 .58 .48 For example, with an evaporation of 8 pounds of steam per pound of coal, and a combustion of 10 pounds of coal per square foot of grate, .43 of a square foot of grate surface per H. P. would be called for. The ratio of heating to grate surface in this type of boiler ranges from 30 to 40, and therefore allows under ordinary conditions a com- bustion of from 8 to 10 pounds of coal per square foot of grate. This is easily obtained with a good chimney draft and careful firing. The larger the boiler, the more important the plant usually, and the greater the care bestowed upon it, so that we may generally count on a higher rate of combustion and a greater efficiency as the size of the boiler increases. Table XII will be found very useful in determining the size of boiler required under different conditions. The grate area is computed for an evaporation of 8 pounds of water per pound 38 HEATING AND VENTILATION TABLE XII DIAMETER OF SHELL IN INCHES NUMBER OF TUBES DIAMETER OF TUBES IN INCHES LENGTH OF TUBES IN FEET HORSE- POWER SIZE OF GRATE IN INCHES SIZE OF UPTAKE IN INCHES SIZE OF SMOKE- PIPE IN SQ. IN 30 28 ^A 6 8.5 24x36 10x14 140 7 9.9 24 x 36 10x14 140 8 11.2 24 x36 10 x 14 140 9 12.6 24 x 42 10x14 140 10 14.0 24x42 10x14 140 36 34 -Y 8 13.6 30x36 10x16 160 9 15.3 30 x 42 10x18 180 10 16.9 30 x 42 10x18 180 11 18.6 30x48 10 x 20 200 12 20.9 30 x 48 10 x 20 200 42 34 3 9 18.5 36x42 10x20 200 10 20.5 36x42 10x20 200 11 22.5 36 x 48 10x25 250 12 24.5 36 x 48 10x25 250 13 26.5 36 x48 10x28 280 14 28.5 36 x 54 10x28 280 48 44 3 10 30.4 42x48 10x28 280 11 33.2 42 x48 10x28 280 12 35.7 42 x 54 10x32 320 . 13 38.3 42x54 10x32 320 14 40.8 42x60 10x36 360 15 43.4 42 x 60 10x36 360 16 45.9 42x60 10x36 360 54 54 3 11 34.6 48 x 54 10x38 380 12 87.7 48 x 54 10x38 380 13 40.8 48 x 54 10x38 880 14 43.9 48x54 10x38 380 15 47.0 48x60 10x40 400 16 50.1 48 x60 10x40 400 46 1 A 17 53.0 48x60 10x40 400 60 72 3 12 48.4 54x60 12x40 460 13 52.4 54x60 12x40 460 14 56.4 54 x60 12x40 460 15 60.4 54x66 12x42 500 16 64.4 54x66 12x42 500 64 Syf, 17 71.4 54 x 72 12x48 550 18 75.6 54 x 72 12x48 550 66 90 8 14 70.1 60x66 12x48 500 15 75.0 60x72 12x52 626 16 80.0 60x72 12x52 620 78 &i/2 17 86.0 60 x 78 12x56 670 18 91.1 60x78 12x56 670 19 96.2 60 x 78 12x56 670 6*2 4 20 93.1 60x78 12x56 670 72 114 3 14 87.4 66x72 12x56 670 15 93.6 66x72 12x56 670 16 99.7 66 x78 12 x 62 . 740 98 3J4 17 106.4 66 x 78 12x62 740 18 112.6 66 x84 12x66 790 19 118.8 66x84 12 x66 790 72 4 20 107.3 66x84 12x66 790 HEATING AND VENTILATION 39 of coal, which corresponds to an efficiency of about 60 per cent, and is about the average obtained in practice for heating boilers. The areas of uptake and smoke-pipe are figured on a basis of 1 square foot to 7 square feet of grate surface, and the results given in round numbers. 'In the smaller sizes the relative size of smoke- pipe is greater. The rate of combustion runs from 6 pounds in the smaller sizes to 11 J in the larger. Boilers of the proportions given in the table, correspond well with those used in actual practice, and may be relied upon to give good results under all ordinary conditions. Water-tube boilers are often used for heating purposes, but more especially in connection with power plants. The method of com- puting the required H. P. is the same as for tubular boilers. Sectional Boilers. Fig. 13 shows a common form of cast-iron boiler. It is made up of slabs or sections, each one of which is con- nected by nipples with headers at the sides and top. The top header acts as a steam drum, and the lower ones act as mud drums ; they also receive the water of condensation from the radiators. The gases from the fire pass backward and forward through flues and are finally taken off at the rear of the boiler. Another common form of sectional boiler is shown in Fig. 14. It is made up of sections which increase the length like the one just described. These boilers have no drum connecting with the sections; but instead, each section connects with the adjacent one through openings at the top and bottom, as shown. The ratio of heating to grate surface in boilers of this type ranges from 15 to 25 in the best makes. They are provided with the usual attachments, such as pressure-gauge, water-glass, gauge-cocks, and safety-valve ; a low-pressure damper regulator is furnished for operat- ing the draft doors, thus keeping the steam pressure practically con- stant. A pressure of from 1 to 5 pounds is usually carried on these boilers, depending upon the outside temperature. The usual setting is simply a covering of some kind of non-conducting material like plastic magnesia or asbestos, although some forms are enclosed in light brickwork. In computing the required size, we may proceed in the same manner as in the case of a furnace. For the best types of house- heating boilers, we may assume a combustion of 5 pounds of coal per square foot of grate per hour, and an average efficiency of 60 per cent, 40 HEATING AND VENTILATION which corresponds to 8,000 B. T. U. per pound of coal, available for useful work. In the case of direct-steam heating, we have only to supply heat to offset that lost by radiation and conduction; so that the grate ares may be found by dividing the computed heat loss per hour by 8,000, which gives the number of pounds of coal; and this in turn, divided by 5, will give the area of grate required. The most efficient rate of Pig. 13. Common Type of Cast-Iron Sectional Boiler. J*ote Headers at Sides and Top Acting as Drums. combustion will depend somewhat upon the ratio between the grate and heating surface. It has been found by experience that about J of a pound of "coal per hour for each square foot of heating surface gives the best results ; so that, by knowing the ratio of heating surface to grate area for any make of heater, we can easily compute the most efficient rate of combustion, and from it determine the necessary grate area. HEATING AND VENTILATION 41 For example, suppose the heat loss from a building to be 480,000 B. T. U. per hour, and that we wish to use a heater in which the ratio of heating surface to grate area is 24. What will be the most efficient rate of combustion and the required ^^^^^ grate area? 480,060 -=- 8,000 = 60 pounds of coal per hour, and 24 -=- 4 = 6, which is the best rate of com- bustion to employ; therefore 60 -T- 6 = 10, the grate area required. There are many different designs of cast-iron boilers for low-pressure steam and hot-water heating. In gen- eral, boilers having a drum connected by nipples with each section give dryer steam and hold a steadier water- line than the second form, especially when forced above their normal ca- pacity. The steam, in passing through the openings between successive -'sec- tions in order to reach the outlet, is apt to carry with it more or less water, and to choke the openings, thus producing an uneven pressure in different parts of the boiler. In the case of hot-water boilers this objection disappears.- In order to adapt this type of boiler to steam work, the opening between the sections should be of good size, with an ample steam space above the water-line; and the nozzles for the discharge of steam should be located at frequent intervals. Fig. 14. Another Type of Sectional Boiler. Here there are no drums, the sections being directly connected through open- ings at top and bottom. Courtesy of American Jtadiator Co. EXAMPLES FOR PRACTICE 1. The heat loss from a building is 240,000 B. T. U. per hour, and the ratio of heating to grate area in the heater to be used is 20. What will be the required grate area? Axs. 6 sq. ft. 2. The heat loss from a building is 168,000 B. T. U. per hour, and the chimney draft is such that not over 3 pounds of coal per hour can be burned per square foot of grate. What ratio of heating to grate area will be necessary, and what will be the required grate area? ANS. Ratio, 12. Grate area, 7 sq. ft, 42 HEATING AND VENTILATION Cast-iron sectional boilers are used for dwelling-houses, small schoolhouses, churches, etc., where low pressures are carried. They are increased in size by adding more slabs or sections. After a certain length is reached, the rear sections become less and less efficient, thus limiting the size and power. Horse=Power for Ventilation. We already know that one B. TU. will raise the temperature of 1 cubic foot of air 55 degrees, or it will raise 100 cubic feet y-J-g- of 55 degrees, or T 5 7 5 F of 1 degree; therefore, to raise 100 cubic feet 1 degree, it will take 1 -r- y/g-, or -y/ B. T.U.; and to raise 100 cubic feet through 100 degrees, it will take Yff- X 100 B. T. U. In other words, the B. T. U. required to raise any given volume of air through any number of degrees in tempera- ture, is equal to Volume of air in cubic ft. X Degrees raised 55 Example. How many B. T. U. are required to raise 100,000 cubic feet of air 70 degrees? m '< X 70 = 127,272 + oo To compute the H. P. required for the ventilation of a building, we multiply the total air-supply, in cubic feet per hour, by the number of degrees through which it is to be raised, and divide the result by 55. This gives the B. T. U. per hour, which, divided by 33,000, will give the H. P. required. In using this rule, always take the air-supply in cubic feet per hour. EXAMPLES FOR PRACTICE 1. The heat loss from a building is 1,650,000 B. T. U. per hour. There is to be an air-supply of 1,500,000 cubic feet per hour, raised through 70 degrees. What is the total boiler H. P. required? ANS. 108. 2. A high school has 10 classrooms, each occupied by 50 pupils. Air is to be delivered to the rooms at a temperature of 70 degrees. What will be the total H. P. required to heat and ventilate the building when it is 10 degrees below zero, if the heat loss through walls and windows is 1,320,000 B. T. U. per hour? ANS. 106 + . DIRECT=STEAM HEATING A system of direct-steam heating consists (1) of a furnace and HEATING AND VENTILATION 43 boiler for the combustion of fuel and the generation of steam; (2) a system of pipes for conveying the steam to the radiators and for returning the water of condensation to the boiler; and (3) radiators or coils placed in the rooms for diffusing the heat. Various types of boilers are used, depending upon the size and kind of building to be warmed. Some form of cast-iron sectional boiler is commonly used for dwelling-houses, while the tubular or water-tube boiler is more usually employed in larger buildings. Where the boiler is used for heating purposes only, a low steam-pres- sure of from 2 to 10 pounds is carried, and the condensation flows back by gravity to the boiler, which is placed below the lowest radiator. When, for any reason, a higher pressure is required, the steam for the heating system is made to pass through a reducing valve, and the condensation is returned to the boiler by means of a pump or return trap. Types of Radiating Surface. The radiation used indirect-steam heating is made up of cast-iron radiators of various forms, pipe radiators, and circulation coils. Cast=Iron Radiators. The general form of a cast-iron sec- tional radiator is shown in Fig. 15. Radiators of this type are made up of sections, the number depending upon the amount of heating surface required. Fig. 16 shows an intermediate section of a radiator of this type. It is simply a loop with inlet and outlet at the bottom. The end sections are the same, except that they have legs, as shown in Fig. 17. These sections are connected at the bottom by special nipples, so that steam entering at the end fills the bottom of the radiator, and, being lighter than the air, rises through the loops and forces the air downward and toward the farther end, where it is dis-. charged through an air-valve placed about midway of the last section. There are many different designs varying in height and width, to Fig. 15. Common Type of Cast-Iron Sectional Radiator. 44 HEATING AND VENTILATION suit all conditions. The wall pattern shown in Fig. 18 is very con- venient when it is desired to place the radiator above the floor, as in bathrooms, etc.; it is also a con- venient form to place under the windows of halls and churches to counteract the effect of cold down drafts. It is adapted to nearly every place where the or- dinary direct radiator can be used, and may be connected up in different ways to* meet the va- rious requirements. A low and moderately shallow radiator, with ample space for the circulation of air between the sections, is more efficient than a deep radiator with the sections closely packed together. One- and two-column radiators, so called, are preferable to three- and four-column, when there is sufficient space to use them. Fig. 16. Fig. 17. Intermediate and End Sections of Radiator Shown in Fig. 15. The end sections (at right) have legs. Fig. 18. Cast-Iron Sectional Radiator of Wall Pattern. The standard height of a radiator is 36 or 38 inches, and, if possible, it is better not to exceed this. HEATING AND VENTILATION 45 For small radiators, it is better practice to use lower sections and increase the length; this makes the radiator slightly more efficient and gives a much better appearance. To get the best results from wall radiators, they should be set out at least \\ inches from the wall to allow a free circulation of air back of them. Patterns having cross-bars should be placed, if possible, with the bars in a vertical position, as their efficiency is impaired somewhat when placed horizontally. Pipe Radiators. This type of radiator (see Fig. 19) is made up of wrought-iron pipes screwed into a cast- iron base. The pipes are eithercon- nected in pairs at the top by return bends, or each sep- arate tube has a thin metal dia- phragm passing up the center nearly to the top. It is nec- essary that a loop be formed, else a 1 'dead end" would occur. This would become filled with air and prevent steam from enter- ing, thus causing portions of the radiator to remain cold. Circulation Coils. These are usually made up of 1 or IJ-inch wrought-iron pipe, and may be hung on the walls of a room by means of hook plates, or suspended overhead on hangers and rolls. Fig. 20 shows a common form for schoolhouse and similar work; this coil is usually made of IJ-inch pipe screwed into headers or branch tees at the ends, and is hung on the wall just below the windows. This is known as a branch coil. Fig. 21 shows a trombone coil, which is commonly used when the pipes cannot turn a corner, and where the entire coil must be placed upon one side of the room. Fig. 22 Fig. 19. Wrought-Irou Pipe Radiator. 46 HEATING AND VENTILATION is called a miter coil, and is used under the same conditions as a trom- bone coil if there is room for the vertical portion. This form is not so pleasing in appearance as either of the other two, and is found only in factories or shops, where looks are of minor importance. Fig. 20. Common Form of "Branch" Coil for Circulation of Direct Steam. Overhead coils are usually of the miter form, laid on the side and suspended about a foot from the ceiling; they are less efficient than when placed nearer the floor, as the warm air stays at the ceiling and the lower part of the room is likely to remain cold. They are used D Fig. 21. "Trombone" Coil. Used where Entire Coil must be Placed on One Side of Room only when wall coils or radiators would be in the way of fixtures, or when they w r ould come below the water-line of the boiler if placed near the floor. When steam is first turned on a coil, it usually passes through a Fig. 22. 'Miter" Coil. Adapted, like the "Trombone," Only to a Single Wall. Frequently Used in Factories and Shops. portion of the pipes first and heats them while the others remain cold and full of air. Therefore the coil must always be made up in such a way that each pipe shall have a certain amount of spring and may expand independently without bringing undue strains upon the others. Circulation coils should incline about 1 inch in 20 feet toward the HEATING AND VENTILATION 47 return end in order to secure proper drainage and quietness of opera- tion. Efficiency of Radiators. The efficiency of a radiator that is, the B. T. U. which it gives off per square foot of surface per hour depends upon the difference in temperature between the steam in the radiator and the surrounding air, the velocity of the air over the radiator, and the quality of the surface, whether smooth or rough. In ordinary low-pressure heating, the first condition is practically constant; but the second varies somewhat with the pattern of the radiator. An open design which allows the air to circulate freely over the radiating surfaces, is more efficient than a closed pattern, and for this reason a pipe coil is more efficient than a radiator. In a large number of tests of cast-iron and pipe radiators, working under usual conditions, the heat given off per square foot of surface per hour for each degree difference in temperature between the steam and surrounding air was found to average about 1 . 7 B. T. U. The temperature of steam at 3 pounds' pressure is 220 degrees, and 220 70 = 150, which may be taken as the average difference between the temperature of the steam and the air of the room, in ordinary low- pressure work. Taking the above results, we have 150 X 1.7 = 255 B. T. U. as the efficiency of an average cast-iron or pipe radiator. This, for convenient use, may be taken as 250. A circulation coil made up of pipes from 1 to 2 inches in diameter, will easily give off 300 B. T. U. under the same conditions; and a cast-iron wall radiator with ample space back of it should have an efficiency equal to that of a wall coil. While overhead coils have a higher efficiency than cast-iron radiators, their position near the ceiling reduces their effec- tiveness, so that in practice the efficiency should not be taken over 250 B. T. U. per hour at the most. Tabulating the above we have: TABLE XIII Efficiency of Radiators, Coils, etc. TYPE OF RADIATING SURFACE RADIATION PER SQUARE FOOT OF SURFACE PER HOUR Cast-iron Sectional and Pipe Radiators Wall Radiators Ceiling Coils Wall Coils 250 B. T. U. 300 200 to 250 300 " 48 HEATING AND VENTILATION If the radiator is for warming a room which is to be kept at a temperature above or below 70 degrees, or if the steam pressure is greater than 3 pounds, the radiating surface may be changed in the same proportion as the difference in temperature between the steam and the air. For example, if a room is to be kept at a temperature of 60, the efficiency of the radiator becomes -ff-- X 250 == 268; that is, the efficiency varies directly as the difference in temperature between the steam and the air of the room. It is not customary to consider this unless the steam pressure should be raised to 10 or 15 pounds or the temperature of the rooms changed 15 or 20 degrees from the normal. From the above it is easy to compute the size of radiator for any given room. First compute the heat loss per hour by conduction and leakage in the coldest weather; then divide the result by the effi- ciency of the type of radiator to be used. It is customary to make the radiators of such size that they will warm the rooms to 70 degrees in the coldest weather. As the low-temperature limit varies a good deal in different localities, even in the same State, the lowest temperature for which we wish to provide must be settled upon before any calcu- lations are made. In New England and through the Middle and Western States, it is usual to figure on warming a building to 70 degrees when the outside temperature is from zero to 10 degrees below. The different makers of radiators publish in their catalogues, tables giving the square feet of heating surface for different styles and heights, and these can be used in determining the number of sections required for all special cases. If pipe coils are to be used, it becomes necessary to reduce square feet of heating surface to linear feet of pipe; this can be done by means of the factors given below. 13 = linear ft. of 1 -in. pipe O O _ ff ii 1 1 * " o tt tt if ' it 1^-in. 1.6 = " "2 -in. " The size of radiator is made only sufficient to keep the room warm after it is once heated ; and no allowance is made for warming up\ that is, the heat given off by the radiator is just equal to that lost through walls and windows. This condition is offset in two ways HEATING AND VENTILATION 49 first, when the room is cold, the difference in temperature between the steam and the air of the room is greater, and the radiator is more efficient; and second, the radiator is proportioned for the coldest weather, so that for a greater part of the time it is larger than neces- sary. EXAMPLES FOR PRACTICE 1 . The heat loss from a room is 25,000 B. T. U. per hour in the coldest weather. What size of direct radiator will be required? ANS. 100 square feet. 2. A schoolroom is to be warmed with circulation coils of 11- inch pipe. The heat loss is 30,000 B. T. U. per hour. What length of pipe will be required? ANS. 230 linear feet. Location of Radiators. Radiators should, if possible, be placed in the coldest part of the room, as under windows or near outside doors. In living rooms it is often desirable to keep the windows free, in which case the radiators may be placed at one side. Circulation coils are run along the outside wall^ of a room under the windows. Sometimes the position of the radiators is decided by the necessary location of the pipe risers, so that a certain amount of judgment must be used in each special case as to the best arrangement to suit all requirements. Systems of Piping. There are three distinct systems of piping, known as the two-pipe system, the one-pipe relief system, and the one- pipe circuit system, with various modifications of each and combina- tions of the different systems. Fig. 23 shows the arrangement of piping and radiators in the two-pipe system. The steam main leads from the top of the boiler, and the branches are carried along near the basement ceiling. Risers are taken from the supply branches, and carried up to the radiators on the different floors; and return pipes are brought down to the return mains, which should be placed near the basement floor below the water-line of the boiler. Where the building is more than two stories high, radiators in similar positions on different floors are con- nected with the same riser, which may run to the highest floor; and a corresponding return drop connecting with each radiator is carried down beside the riser to the basement. A system in which the main horizontal returns are below the water-line of the boiler is said to 50 HEATING AND VENTILATION have a wet or sealed return. If the returns are overhead and above the water-line, it is called a dry return. Where the steam is exposed to extended surfaces of water, as in overhead returns, where the con- densation partially fills the pipes, there is likely to be cracking or water-hammer, due to the sudden condensation of the steam as it comes in contact with the cooler water. This is especially noticeable when steam is first turned into cold pipes and radiators, and the con- densation is excessive. When dry returns are used, the pipes should be large and have a good pitch toward the boiler. In the case of sealed returns, the only contact between the steam Fig. 23. Arrangement of Piping and Radiators in "Two-Pipe" System. and standing water is in the vertical returns, where the exposed sur- faces are very small (being equal to the sectional area of the pipes), and trouble from water-hammer is practically done away with. Dry returns should be given an incline of at least 1 inch in 10 feet, while for wet returns 1 inch in 20 or even 40 feet is ample. The ends of all steam mains and branches should be dripped into the returns. If the return is sealed, the drip may be directly connected as shown in Fig. 24; but if it is dry, the connection should be provided with a siphon loop as indicated in Fig. 25. The loop becomes filled with water, and prevents steam from flowing directly into the return. As the HEATING AND VENTILATION 51 stea Ret-urr* condensation collects in the loop, it overflows into the return pipe and is carried away. The return pipes in this case are of course filled with steam above the water; but it is steam which has passed through the radiators and their return connections, and is therefore at a slightly lower pressure; so that, if steam were ad- mitted directly from the main, it would tend to hold back the water in more distant returns and cause surging and crack- ing in the pipes. Some- Fig . 24 . Drip frora steam Mai^nnected Directly times the boiler is at a , to sealed Return. lower level than the basement in which the returns are run, and it then becomes necessary to establish a false water-line. This is done by making connections as shown in Fig. 26. It is readily seen that the return water, in order to reach the boiler, must flow through the trap, which raises the water-line or seal to the level shown by the dotted line. The balance pipe is to equalize the pressure above and below the water in the trap, and prevent siphonic action, which would tend to drain the water out of the return mains after a flow was once started. The balance pipe, when possible, should be 15 or 20 feet in length, with a throttle-valve placed near its connection with the main. This valve should be opened just enough to allow the steam-pressure to act upon the air which oc- cupies the space above the water in the trap ; but it should not be opened sufficiently to allow the steam to enter in large volume and drive the air out. The success of this arrangement depends upon keeping a layer or cushion of cool air next to the surface of the water in the trap, and this is easily done by following the method here described. Steam Pig. 25. Use of Siphon in Connecting Drip from Steam Main to a "Dry" Return. 52 HEATING AND VENTILATION One=Pipe Relief System. In this system of piping, the radiators have but a single connection, the steam flowing in and the condensa- tion draining out through the same pipe. Fig. 27 shows the method of running the pipes for this system. The steam main, as before, leads from the top of the boiler, and is carried to as high a point as the basement ceiling will allow; it then slopes downward with a grade of about 1 inch in 10 feet, and makes a circuit of the building or a portion of it. Risers are taken from the top and carried to the radiators above, as in the two-pipe system; but in this case, the condensation flows back through the same pipe, and drains into the return main near the floor through drip connections which are made at frequent in- tervals. In a two-story build- ing, the bottom of each riser to the second floor is dripped; and in larger build- ings, it is cus- tomary to drip each riser that has more than one radiator con- nected with it. If the radiators are large and at a considerable dis- tance from the next riser, it is better to make a drip connection for each radiator. When the return main is overhead, the risers should be dripped through siphon loops; but the ends of the branches should make direct connection with the returns. This is the reverse of the two-pipe system. In this case the lowest pressure is at the ends of the mains, so that steam introduced into the returns at these points will cause no trouble in the pipes connecting between these and the boiler. If no steam is allowed to enter the returns, a vacuum will be formed, and there will be no pressure to force the water back to the Fig. 26. Connections Made to Establish "False" Water-Line when Boiler is below Basement Level. HEATING AND VENTILATION 53 boiler. A check-valve should always be placed in the main return Fig. 27. Arrangement of Piping and Radiators in "One-Pipe Relief" System. near the boiler, to prevent the water from flowing out in case of a vacuum being formed suddenly in the pipes. Fig. 28. Arrangement of Piping and Radiators in "One-Pipe Circuit" System. There is but little difference in the cost of the two systems, as larger pipes and valves are required for the single-pipe method. 54 HEATING AND VENTILATION ^ Siphon Conrectfor\ a i CV\ecU VcLlve Connection^ With radiators of medium size and properly proportioned connections, the single-pipe system in preferable, there being but one valve to operate and only one-half the number of risers passing through the lower rooms. One=Pipe Circuit System. In this case, illustrated in Fig. 28, the steam main rises to the highest point of the basement, as before; and then, with a considerable pitch, makes an entire circuit of the build- ing, and again connects with the boiler below the water-line. Single risers are taken from the top; and the condensa- tion drains back through the same pipes, and is carried along with the flow of steam to the ex- treme end of the main, where it is returned to the boiler. The main is m a d e large, and of the same size throughout its entire length. It must be given a good pitch to insure satisfactory results. One objection to a single-pipe system is that the steam and return water are flowing in opposite directions, and the risers must be made of extra large size to prevent any interference. This is overcome in large buildings by carrying a single riser to the attic, large enough to supply the entire building; then branching and running "drops" to the basement. In this system the flow of steam is downward, as well as that of water. This method of piping may be used with good results in two-pipe systems as well. Care must always be taken that no pockets or low points occur in any of the lines of pipe; but if for any reason they cannot be avoided, they should be carefully drained. A modification of this system, adapting it to large buildings, is shown in diagram in Fig. 29. The riser shown in this case is one of Return Sealed Rel-ur-n Fig. 29. "One-Pipe Circuit" System. Building. Adapted to a Large ROCOCO ORNAMENTAL THREE COLUMN PATTERN RADIATOR FOB WARMING BY HOT WATER. American Radiator Company. HEATING AND VENTILATION 55 several, the number depending upon the size of the building; and may be supplied at either bottom or top as most desirable. If steam is supplied at the bottom of the riser, as shown in the cut, all of the drip connections with the return drop, except the upper one, should Fig. 30. "Two-Pipe" Connection of Radia- tor to Riser and Return. Fig. 31. "Ooe-Pipe" Connection of Radia- tor to Basement Main. be sealed with either a siphon loop or a check-valve, to prevent the steam from short-circuiting and holding back the condensation in the returns above. If an overhead supply is used, the arrangement should be the reverse; that is, all return connections should be sealed except the lowest. Sometimes a separate drip is carried down from each set of radiators, as shown on the lower story, being connected with the main return below the water-line of the boiler. In case this is done, it is well to provide a check-valve in each drip below the water-line. In buildings of any considerable size, it is well to divide the piping system into sections by means of valves placed in the corresponding supply and return branches. These are for use in case of a break in any part of the system, so that it will be necessary to shut off only a small part of the heating system during repairs. In tall buildings, it is customary to place valves at the top and bottom of each riser, for the same purpose. Radiator Connections. Figs. 30, 31, and 32 show the common Fig. 32. "One-Pipe" Connection of Radiator to Riser. 56 HEATING AND VENTILATION methods of making connections between supply pipes and radiators. Fig. 30 shows a two-pipe connection with a riser; the return is carried down to the main below. Fig. 31 shows a single-pipe connection with a basement main; and Fig. 32, a single connection with a riser. Care must always be taken to make the horizontal part of the piping between the radiator and riser as short as possible, and to give it a good pitch toward the riser. There are various ways of making these connections, especially suited to different conditions; but the examples given serve to show the general principle to be followed. Figs. 20, 21, and 22 show the common methods of making steam and return connections with circulation coils. The position of the air-valve is shown in each case. Expansion of Pipes. Cold steam pipes expand approximately Fig. 33. Elevation and Plan of Swivel-Joint to Counteract Effects of Expansion and Contraction in Pipes. 1 inch in each 100 feet in length when, low-pressure steam is turned into them ; so that, in laying out a system of piping, we must arrange it in such a manner that there will be sufficient "spring" or "give" to the pipes to prevent injurious strains. This is done by means of off- sets and bends. In the case of larger pipes this simple method will not be sufficient, and swivel or slip joints must be used to take up the expansion. The method of making up a swivel-joint is shown in Fig. 33. Any lengthening of the pipe A will be taken up by slight turning or swivel movements at the points B and C. A slip-joint is shown in HEATING AND VENTILATION 57 Fig. 34. The part c slides inside the shell d, and is made steam- tight by a stuffing-box, as shown. The pipes are connected at the flanges .4 and B. When pipes pass through 6 Fig. 34. "Slip-Joint" Connection to Take Care of Expansion and Contraction of Pipes. floors or parti- tions, the wood- work should be protected by gal- v a n i z e d-i r o n sleeves having a diameter from f to 1 inch greater than the pipe. Fig. 35 shows a form of adjustable floor-sleeve which may be lengthened or shortened to conform to the thickness of floor or partition. If plain sleeves are used, a plate should be placed around Fig. 35. Adjustable Metal Sleeve for Carrying Pipe through Floor or Partition. Fig. 36. Floor -Plate Adjusted to Plain Sleeve for Carrying Pipe through Floor or Partition. the pipe where it passes through the floor or partition. These are Fig. 37. Angle Valve. Fig. 38. Offset Valve. Valves for Radiator Connections. Fig. 39. Corner Valve. made in two parts so that they may be put in place after the pipe is hung. A plate of this kind is shown in Fig. 36. 58 HEATING AND VENTILATION Valves. The different styles commonly used for radiator con- nections are shown in Figs. 37, 38, and 39, and are known as anylc, offset, and corner valves, respectively. The first is used when the radiator is at the top of a riser or when the connections are like those shown in Figs. 30, 31, and 32$ the second is used when the connection Fig. 40. Indicating Effect of Using Globe Valve on Horizontal Steam Supply Pipe or Dry Return. between the riser and radiator is above the floor; and the third, when the radiator has to be set close in the corner of a room and there is not space for the usual connection. A globe valve should never be used in a horizontal steam supply or dry return. The reason for this is plainly shown in Fig. 40. In order for water to flow through the valve, it must rise to a height shown by the dotted line, which would half fill the pipes, and cause serious trouble from water-hammer. The gate valve shown in Fig. 41 does not have this undesirable fea- ture, as the opening is on a level with the bottom of the pipe. Fig. 41. Gate Valve. Fig. 42. Simplest Form of Air- Valve. Operated by Hand. Air=Valves. Valves of various kinds are used for freeing the radiators from air when steam is turned on. Fig. 42 shows the simplest form, which is operated by hand. Fig. 43 is a type of auto- matic valve, consisting of a shell, which is attached to the radiator. J? is a small opening which may be closed by the spindle (7, which HEATING AND VENTILATION 59 is provided with a conical end. D is a strip composed of a layer of iron or steel and one of brass soldered or brazed together. The action of the valve is as follows : w r hen the radiator is cold and filled with air the valve stands as shown in the cut. When steam is turned on, the air is driven out through the opening B. As soon as this is expelled and steam strikes the strip D, the two prongs spring apart owing to the unequal ex- pansion of the two metals due to the heat of the steam. This raises the spindle C, and closes the opening so that no steam can escape. If air should collect in the valve, and the metal strip twmxmm Fig. 43. Radiator Automatic Air- Valve. Fg. . aaor uomac r- av Operated by Metal Strip D, Consisting of Two Pieces of Metal of Unequal Expansive Power. become cool, it would contract, and the spindle would drop and allow the air to escape through B as before. E is an adjusting nut. F is a float attached to the spindle, and is supposed, in case of a sudden rush of water with the air, to rise and close the opening; this action, however, is some- what uncertain, especially if the pressure of water continues for some time. There are other types of valves acting on the same principle. The valve shown Jfi Nonas:' No. I ft Fig. 44. Automatic Air- Valve. Closed by Expansion of a Piece of Vulcanite. Fig. 45. Automatic Air- Valve. Operated by Expansion of Drum C'Due to Vaporiza- tion of Alcohol with which it is Partly Filled. in Fig. 44 is closed by the expansion of a piece of vulcanite instead of a metal strip, and has no water float. 60 HEATING AND VENTILATION The valve shown in Fig. 45 acts on a somewhat different prin- ciple. The float C is made of thin brass, closed at top and bottom, and is partially filled with wood alcohol. When steam strikes the float, the alcohol is vaporized, and creates a pressure sufficient to bulge out the ends slightly, which raises the spindle and closes the opening B. Fig. 46 shows a form of so-called vacuum valve. It acts in a similar manner to those already described, but has in addition a ball check which prevents the air from being drawn into the radiator, should the steam go down and a vacuum be formed. If a partial vacuum exists in the boiler and radiators, the boiling point, and consequently the tempera- ture of the steam, are lowered, and less heat is given off by the radiators. This method of operating a heating plant is sometimes advo- cated for spring and fall, when little heat is re- quired, and when steam under pressure would overheat the rooms. Pipe Sizes. The proportioning of the steam pipes in a heating plant is of the greatest im- portance, and should be carefully worked out by methods which experience has proved to be correct. There are several ways of doing this; but for ordinary conditions, Tables XIV, XV, and XVI have given excellent results in actual practice. They have been computed from what is known as D'Arcy's formula, with suitable corrections made for actual working conditions. As the computations are somewhat complicated, only the results will be given here, with full directions for their proper use. Table XIV gives the flow of steam in pounds per minute for pipes of different diameters and with varying drops in pressure be- tween the supply and discharge ends of the pipe. These quantities are for pipes IjOO feet in length; for other lengths the results must be corrected by the factors given in Table XVI. As the length of pipe increases, friction becomes greater, and the quantity of steam dis- charged in a given time is diminished. Table XIV is computed on the assumption that the drop in Fig. 46. Vacuum Valve. HEATING AND VENTILATION 61 TABLE XIV Flow of Steam in Pipes of Various Sizes, with Various Drops in Pres> sure between Supply and Discharge Ends Calculated for 100-Foot Lengths of Pipe DROP IN PRESSURE (POUNDS) H 1 A H 1 1^ 2 3 4 5 1 .44 .63 .78 91 1.13 1.31 1.66 1.97 2.26 1M .81 1.16 1.43 1.66 2.05 2.39 3.02 3.59 4.12 i^ 1.06 1.89 2.34 2.71 3.36 3.92 4.94 5.88 6.75 2 2.93 4.17 5.16 5.99 7.43 8.65 10.9 13.0 14.9 2y 2 5.29 7.52 9.32 10.8 13.4 15.6 19.7 23.4 26.9 3 8.61 12.3 15.2 17.6 21.8 25.4 32 31.8 43.7 zy 2 12.9 18.3 22.6 26.3 32.5 37.9 47.8 56.9 65.3 4 181 25.7 31.8 36.9 45.8 53.3 67.2 80.1 91.9 5 32.2 45.7 56.6 65.7 81.3 94.7 120 142 163 6 51.7 73.3 90.9 106 131 152 192 229 262 7 76.7 109 135 157 194 226 285 339 390 8 108 154 190 222 274 319 402 478 549 9 147 209 258 299 371 432 545 649 745 10 192 273 339 393 487 567 715 852 977 12 305 434 537 623 771 899 1,130 1,350 1,550 15 535 761 942 1,090 1,350 1,580 1,990 2,370 2,720 pressure between the two ends of 'the pipe equals the initial pressure. If the drop in pressure is less than the initial pressure, the actual discharge will be slightly greater than the quantities given in the table; TABLE XV Factors for Calculating Flow of Steam in Pipes under Initial Pres- sures above Five Pounds To be used in connection with Table XIV DROP IN INITIAL, PRESSURE (POUNDS) PRESSURE IN POUNDS 10 20 30 40 60 80 \ 1.27 1.49 1.68 1.84 2.13 2.38 ! 1.26 1.48 1.66 1.83 2.11 2.36 1.24 1.46 1.64 1.80 2.08 2.32 2 1.21 1.41 1.59 1.75 2.02 2.26 3 1.17 1.37 1.55 1.70 1.97 2.20 4 1.14 1.34 1.51 1.66 1 ,92 2.14 5 1.12 1.31 1.47 1.62 1.87 2.09 but this difference will be small for pressures up to 5 pounds, and may be neglected, as it is on the side of safety. For higher initial pressures, Table XV has been prepared. This is to be used in connection with Table XIV as follows: First find from Table XIV the quantity of steam which will be discharged through the given diameter of pipe 62 HEATING AND VENTILATION TABLE XVI Factors for Calculating Flow of Steam in Pipes of Other Lengths than 100 Feet FEET FACTOR FEET FACTOR FEET FACTPR FEET FACTOR 10 3.16 120 .91 275 ' .60 600 .40 20 2.24 130 .87 300 .57 650 .39 30 1.82 140 .84 325 .55 700 .37 40 1.58 150 .81 350 .53 750 .36 50 1.41 160 .79 375 .51 800 .35 60 1.29 170 .76 400 .50 850 .34 70 1.20 180 .74 425 .48 900 .33 80 1.12 190 .72 450 .47 950 .32 90 1.05 200 .70 475 .46 1,000 .31 100 1.00 225 .66 500 .45 110 .95 250 .63 550 .42 with the assumed drop in pressure; then look in Table XV for the factor corresponding with the assumed drop and the higher initial pressure to be used. The quantity given in Table XIV, multiplied by this factor, will give the actual capacity of the pipe under the given conditions. Example What weight of steam will be discharged through a 3-inch pipe 100 feet long, with an initial pressure of 60 pounds and a drop of 2 pounds? Looking in Table XIV, we find that a 3-inch pipe will dis- charge 25 . 4 pounds of steam per minute with a 2-pound drop. Then looking in Table XV, we find the factor corresponding to 60 pounds initial pressure and a drop of 2 pounds to be 2.02. Then according to the rule given, 25.4 X 2.02 = 51. 3 pounds, which is the capacity of a 3-inch pipe under the assumed conditions. Sometimes the problem will be presented in the following way: What size of pipe will be required to deliver 80 pounds of steam a distance of 100 feet with an initial pressure of 40 pounds and a drop of 3 pounds? We have seen that the higher the initial pressure with a given drop, the greater will be the quantity of steam discharged ; therefore a smaller pipe will be required to deliver 80 pounds of steam at 40 pounds than at 3 pounds initial pressure From Table XV, we find that a given pipe will discharge 1 . 7 times as much steam per minute with a pressure of 40 pounds and a drop of 3 pounds, as it would with a pressure of 3 pounds, dropping to zero. From this it is evident that if we divide 80 by 1 .7 and look in Table XIV under "3 pounds ivc.r*oii i m Of J ALFOR^X HEATING AND VENTILATION 63 drop" for the result thus obtained, the size of pipe corresponding will be that required. Now, 80 -f- 1 .7 = 47. The nearest number in the table marked "3 pounds drop" is 47.8, which corresponds to a 3J- inch pipe, which i% the size required. These conditions will seldom be met with in low-pressure heating, but apply more particularly to combination power and heating plants, and will be taken up more fully under that head. For lengths of pipe other than 100 feet, multiply the quantities given in Table XIV by the factors found in Table XVI. Example What weight of steam will be discharged per minute through a 3^-inch pipe 450 feet long, with a pressure of 5 pounds and a drop of J pound? Table XIV, which may be used for all pressures below 10 pounds, gives for a 3J-inch pipe 100 feet long, a capacity of 18.3 pounds for the above conditions. Looking in Table XVI, we find the correction factor for 450 feet to be .47. Then 18.3 X .47 = 8.6 pounds, the quantity of steam which will be discharged if the pipe is 450 feet long. Examples involving the use of Tables XIV, XV, and XVI in combination, are quite common in practice. The following example will show the method of calculation: What size of pipe will be required to deliver 90 pounds of steam per minute a distance of 800 feet, with an initial pressure of 80 pounds and a drop of 5 pounds? Table XVI gives the factor for 800 feet as .35, and Table XV, that for 80 pounds pressure and 5 pounds drop, as 2.09. Then 90 = 123, which is the equivalent quantity we must look . oo /\ iL . uy for in Table XIV. We find that a 4-inch pipe will discharge 91.9 pounds, and a 5-inch pipe 163 pounds. A 4^-inch pipe is not com- monly carried in stock, and we should probably use a 5-inch in this case, unless it was decided to use a 4-inch and allow a slightly greater drop in pressure. In ordinary heating work, with pressures varying from 2 to 5 pounds, a drop of J pound in 100 feet has been found to give satisfactory results. In computing the pipe sizes for a heating system by the above methods, it would be a long process to work out the size of each branch separately. Accordingly Table XVII has been prepared for ready use in low-pressure work. 64 HEATING AND VENTILATION As most direct heating systems, and especially those in school- houses, are made up of both radiators and circulation coils, an effi- ciency of 300 B. T. U. has been taken for direct radiation of whatever variety, no distinction being made between the different kinds. This gives a slightly larger pipe than is necessary for cast-iron radiators; but it is probably offset by bends in the pipes, and in any case gives a slight factor of safety. We find from a steam table that the latent heat of steam at 20 pounds above a vacuum (which corresponds to 5 pounds' gauge-pressure) is 954 + B. T. U. which means that, for every pound of steam condensed in a "radiator, 954 B. T. U. are given off for warming the air of the room. If a radiator has an efficiency of 300 B. T. U., then each square foot of surface will condense 300 -r- 954 = .314 pound of steam per hour; so that we may assume in round numbers a condensation of J of a pound of steam per hour for each square foot of direct radiation, when computing the sizes, of steam pipes in low-pressure heating. Table XVII has been calculated on this assumption, and gives the square feet of heating surface TABLE XVII Heating Surface Supplied by Pipes of Various Sizes Length of Pipe, 100 Feet SQUARE FEET OP HEATING SURFACE C!, ,.., T> ti.r. i Pound Drop \ Pound Drop 1 80 114 it 145 190 210 340 2 525 750 2* 950 1,350 3 1,550 2,210 3* 2,320 3,290 4 3,250 4,620 5 5,800 8,220 6 9,320 13,200 7 13,800 19,620 8 19,440 27,720 which different- sizes of pipe will supply, with drops in pressure of \ and \ pounds in each 100 feet of pipe. The former should be used for pressures from 1 to 5 pounds, and the latter may be used for pressures over 5 pounds, under ordinary conditions. The sizes of long mains and special pipes of large size should be proportioned directly from Tables XIV, XV, and XVI. HEATING AND VENTILATION Where the two-pipe system is used and the radiators have sepa- rate supply and return pipes, the risers or vertical pipes may be taken from Table XVII; but if the single-pipe system is used, the risers must be increased jn size, as the steam and water are flowing in oppo- site directions and 'must have plenty of room to pass each other. It is customary in this case to base the computation on the velocity of the steam in the pipes, rather than on the drop in pressure. Assum- ing, as before, a condensation of one-third of a pound of steam per hour per square foot of radiation, Tables XVIII and XIX have been prepared for velocities of 10 and 15 feet per second. The sizes given in Table XIX have been found sufficient in most cases; but the larger sizes, based on a flow of 10 feet per second, give greater safety and should be more generally used. The size of the largest riser should usually be limited to 2J inches in school and dwelling-house work, unless it is a special pipe carried up in a concealed position. If the length of riser is short between the lowest radiator and the main, a higher velocity of 20 feet or more may be allowed through this por- tion, rather than make the pipe excessively large. TABLE XVIII TABLE XIX Radiating Surface Supplied by Steam Risers 10 FEET PER Si ,COND VELOCITY 15 FEET PER Si :COND VELOCITY Size of Pipe Sq. Feet of Radiation Size of Pipe Sq. Feet of Radiation 1 in. 30 1 n. 50 H 60 H 90 1* 80 H 120 2 130 2 200 2* 190 2* 290 3 290 3 340 3* 390 3* 590 EXAMPLES FOR PRACTICE 1. How many pounds of steam will be delivered per minute, through a 3J-inch pipe 600 feet long, with an initial pressure of 5 pounds and a drop of \ pound? ANS. 7.32 pounds. 2. What size pipe will be required to deliver 25.52 pounds of steam per minute with an initial pressure of 3 pounds and a drop of \ pound, the length of the pipe being 50 feet? ANS. 4-inch. 3. Compute the size of pipe required to supply 10,000 square feet of direct radiation (assume J of a pound of steam per square 66 HEATING AND VENTILATION foot per hour) where the distance to the boiler house is 300 feet, and the pressure carried is 10 pounds, allowing a drop in pressure of 4 pounds. ANS. 5-inch (this is slightly larger than is required, while a 4-inch is much too small). TABLE XX Sizes of Returns for Steam Pipes (in Inches) DIAMETER OF STEAM PIPE DIAMETER OF DRY RETURN DIAMETER OF SEALED RETURN 1 1 i 11 1 li H i 2" H U 2* 2" H 3 2J . 2 3* 2 4 3 2* 5 3 2* 6 3*. 3 7 3i 3 8 4 3* 9 5 3* 10 5 4 12 6 5 Returns. The size of return pipes is usually a matter of custom and judgment rather than computation. It is a common rule among steamfitters to make the returns one size smaller than the corre- sponding steam pipes. This is a good rule for the smaller sizes, but gives a larger return than is necessary for the larger sizes of pipe. Table XX gives different sizes of steam pipes with the corresponding diameters for dry and sealed returns. TABLE XXI Pipe Sizes for Radiator Connections SQUARE FEET OF RADIATION STEAM RETURN 10 to 30 f inch f inch Two-Pipe 30 to 48 48 to 96 1 a. I 1C 96 to 150 H " n " 10 to 24 1 inch Single-Pipe 24 to 60 60 to 80 11 " H " . 80 to 130 2 " HEATING AND VENTILATIQN The length of run and number of turns in a return pipe should be noted, and any unusual conditions provided for. Where the condensation is discharged through a trap into a lower pressure, the sizes given may be^ slightly reduced, especially among the larger sizes, depending upon the differences in pressure. Radiators are usually tapped for pipe connections as shown in Table XXI, and these sizes may be used for the connections with the mains or risers. Boiler Connections. The steam main should be connected to the rear nozzle, if a tubular boiler is used, as the boiling of the water is less violent at this point and dryer steam will be obtained. The shut- off valve should be placed in such a position that pockets for the accumulation of condensation will be avoided. Fig. 47 shows a good position for the valve. The size of steam connection may be computed by means of the methods already given, if desired. But for convenience the sizes given in Table XXII may be used with satisfactory results for the short runs between the boilers and main header. TABLE XXII Pipe Sizes from Boiler to Main Header Fig 47. Good Position for Shut-Off Valve. DIAMETER OP BOILER SIZE OF STEAM PIPE 36 inches 3 inches 42 4 48 4 54 5 60 5 66 6 72 " 6 The return connection is made through the blow-off pipe, and should be arranged so that the boiler can be blown off without draining the returns. A check-valve should be placed in the main return, and a plug-cock in the blow-off pipe. Fig. 48 shows in plan a good arrangement for these connections. HEATING AND VENTILATION The ,feed connections, with the exception of that part exposed in the smoke-bonnet, are always made of brass in the best. class of work. The small section referred to should be of extra heavy wrought 4//4AV RETURN TO DRAIN OR ^ Fig. 48. A Good Arrangement of Return and Blow-Off Connections. iron. The branch to each boiler should be provided with a gate or globe valve and a check-valve, the former being placed next to the boiler. Table XXIII gives suitable sizes for return, blow-off, and feed pipes for boilers of different diameters. TABLE XXIII Sizes for Return, Blow-Off, and Feed Pipes DIAMETER OF BOILER SIZE OF PIPE FOR GRAVITY RETURN SIZE OF BLOW-OFF PIPE SIZE OF FEED PIPE 36 inches 1^ inches \\ inches 1 inch 42 2 H ' 1 48 2 1* 1 54 2* 2 H 60 2i 2 H 66 3 2* ' 1* 72 3 2* ' U Blow=0ff Tank. Where the blow-off pipe connects with a sewer, some means must be provided for cooling the water, or the expansion and contraction caused by the hot water flowing through the drain-pipes will start the joints and cause leaks. For this reason it is customary to pass the water through a blow-off tank. A form of wrought-iron tank is shown in Fig. 49. It consists of a receiver supported on cast-iron cradles. The tank ordinarily stands nearly full of cold water. The pipe from the boiler enters above the water-line, and the sewer connection leads from near the bottom, as shown. A vapor pipe is carried from the top of the tank above the roof of the building. When water from the boiler is blown into the tank, cold water from HEATING AND VENTILATION 69 the bottom flows into the sewer, and the steam is carried off through the vapor pipe. The equalizing pipe is to prevent any siphon action which might draw the water out of the tank after a flow is once started. As only a part of the water is blown out of a boiler at one time, the blow-off tank can be'-of a comparatively small size. A tank 24 by 48 inches should be large enough for boilers up to 48 inches in diameter; Fig. 49. Connections of Blow-Off Tank. and one 36 by 72 inches should care for a boiler 72 inches in diameter. If smaller quantities of water are blown off at one time, smaller tanks can be used. The sizes given above are sufficient for batteries of 2 or more boilers, as one boiler can be blown off and the water allowed to cool before a second one is blown off. Cast-iron tanks are often used in place of wrought-iron, and these may be sunk in the ground if desired. '... Cast Iron Seamless Tubular Steam Heater. HEATING AND VENTILATION PART II INDIRECT STEAM HEATING As already stated, in the indirect method of steam heating, a special form of heater is placed beneath the floor, and encased in galvanized iron or in brickwork: A cold-air box is connected with the space beneath the heater; and warm-air pipes at the' top are connected with registers in the floors or walls as already described for furnaces. A separate heater may be provided for each register if the rooms are large, or two or more registers may be connected with the same heater if the horizontal runs of pipe are short. Fig. 50 shows a section through a heater arranged for introducing hot air into a room through a floor register; and -Fig. 51 shows the same type of heater connected with a wall register. The cold-air box is seen at the bottom of the casing; and the air, in passing through the spaces between the sections of the heater, becomes warmed, and rises to the rooms above. Different forms of indirect heaters are shown in Figs. 52 and 53. Several sections con- nected in a single group are called a stack. Some- times the stacks are en- cased in brickwork built up from the basement floor, instead of in gal- vanized iron as shown in the cuts. This method of heating provides fresh air for ventilation, and for this reason is especially adapted for schoolhouses, hospitals, churches, etc. As com- pared with furnace heating, it has the advantage of being less affected by outside wind-pressure, as long runs of horizontal pipe Fig. 50. Steam Heater Placed under Floor Register Indirect System. 72 HEATING AND VENTILATION are avoided and the heaters can be placed near the registers. In a large building where several furnaces would be required, a single boiler can be used, and the num- ber of stacks increased to suit the existing conditions, thus making it necessary to run but a single fire. Another advan- tage is the large ratio between the heating and grate surface as compared with a furnace; and as a result, a large quan- tity of air is warmed to a mod- erate temperature, in place of a smaller quantity heated to a much higher temperature. This gives a more agreeable quality to the air, and renders it less dry. Direct and indi- rect systems are often com- bined, thus providing the liv- ing rooms with ventilation, while the hallways, corridors, etc., have only direct radiators for warming. Types of Heaters. Various forms of indirect radiators are shown in Figs. 52, 53, 54, and 56. A hot-water radiator may be used for steam; but a steam radiator cannot always be used for hot water, as Fig. 51. Steam Heater Connected to Wall Reg- ister. Indirect System. Fig. 52. One Form of Indirect Steam or Hot- Water Heater. it must be especially designed to produce a continuous flow of water through it from top to bottom. Figs. 54 and 55 show the outside and the interior construction of a common pattern of indirect radiator HEATING AND VENTILATION 73 designed especially for steam. The arrows in Fig. 55 indicate the path of the steam through the radiator, which is supplied at the right, while the return connection is at the left. The air-valve in this case should be connected in the end of the last section near the return. Fig. 53. Another Form of Indirect Steam or Hot Water Heater. A very efficient form of radiator, and one that is especially adapted to the warming of large volumes of air, as in schoolhouse work, is shown in Fig. 56, and is known as the School pin radiator. This can Fig. 54. Exterior View of a Common Type of Radiator for Indirect-Steam Heating. be used for either steam or hot water, as there is a continuous passage downward from the supply connection at the top to the return at the bottom. These sections or slabs are made up in stacks after the Fig. 55. Interior Mechanism of Radiator Shown in Fig. 54. manner shown in Fig. 57, which represents an end view of several sections connected together with special nipples. A very efficient form of indirect heater may be made up of wrought-iron pipe joined together with branch tees and return bends. 74 HEATING ANP VENTILATION A heater like that shown in Fig. 58 is known as a box coil. Its effi- ciency is increased if the pipes are staggered that is, if the pipes in alternate rows are placed over the spaces between those in the row below. Efficiency of Heaters. The efficiency of an indirect heater Fig. 56. "School Pin" Radiator, Especially Adapted for Warming Large Volumes of Air by Either Steam or Hot Water. depends upon its form, the difference in temperature between the steam and the surrounding air, and the velocity with which the air passes over the heater. Under ordinary conditions in dwelling-house work, a good form of indirect radiator will give off about 2 B. T. U. per square foot per hour for each degree difference in tem- perature between the .steam and the entering air. Assum- ing a steam pressure of 2 pounds and an outside tem- perature of zero, we should have a difference in tempera- ture of about 220 degrees, which, under the conditions stated, would give an efficiency of 220 X 2 = 440 B. T. U. per hour for each square foot of radiation. By making a similar computation for 10 degrees be- low zero, we find the efficiency to be 460. In the same manner we may calculate the efficiency for varying conditions of steam pressure and outside temperature.. In the case of schoolhouses and similar buildings where large volumes of air are warmed to a moderate tern- Fig. 57. End View of Several "School Pin' Radiator Sections Connected Together. HEATING AND VENTILATION 75 perature, a somewhat higher efficiency is obtained, owing to the in- creased velocity of the air over the heaters. Where efficiencies of 440 and 460 are used for dwellings, we may substitute 600 and 620 for schoolhoiises. This corresponds approximately to 2.7 B. T. U. per square foot per hour for a difference of 1 degree between the air and steam. The principles involved in indirect steam heating are similar to those already described in furnace heating. Part of the heat given off by the radiator must be used in warming up the air-supply to the temperature of the room, and part for offsetting the loss by conduction through walls and windows. The method of computing the heating surface required, depends upon the volume of air to be supplied to the room. In the case of a schoolroom or hall, where the air quantity ** A . . ^ Fig. 58. "Box Coil," Built Up of Wrought-Iron Pipe, for Indirect- Steam Heating. is large as compared with the exposed wall and window surface, we should proceed as follows: First compute the B. T. U. required for loss by conduction through walls and windows; and to this, add the B. T. U. required for the necessary ventilation; and divide the sum by the efficiency of the radiators. An example will make this clear. Example. How many square feet of indirect radiation will be required to warm and ventilate a schoolroom in zero weather, where the heat loss by conduction through walls and windows is 36,000 B. T. U., and the air-supply is 100,000 cubic feet per hour? By the methods given under "Heat for Ventilation/' we have 100,000 X 70 x 12 7,272 - B. T. U. required for ventilation. 36,000 + 127,272 = 163,272 B. T. U. = Total heat required. This in turn divided by 600 (the efficiency of indirect radiators under these conditions) gives 272 square feet of surface required. 76 HEATING AND VENTILATION In the case of a dwelling-house the conditions are somewhat changed, for a room having a comparatively large exposure will have perhaps only 2 or 3 occupants, so that, if the small air-quantity neces- sary in this case were used to convey the required amount or heat to the room, it would have to be raised to an excessively high temper- ature. It has been found by experience that the radiating surface necessary for indirect heating is about 50 per cent greater than that required for direct heating. So for this work we may compute the surface required for direct radiation, and multiply the result by 1.5. Buildings like hospitals are in a class between dwellings and schoolhouses. The air-supply is based on the number of occupants, as in schools, but other conditions conform more nearly to dwelling- houses. To obtain the radiating surface for buildings of this class, we compute the total heat required for warming and ventilation as in the case of schoolhouses, and divide the sum by the efficiencies given for dwellings that is, 440 for zero weather, and 460 for 10 degrees below. Example. A hospital ward requires 50,000 cubic feet of air per hour for ventilation; and the heat loss by conduction through walls, etc., is 100,000 B. T. U. per hour. How many square feet of indirect radiation will be required to warm the ward in zero weather? 50,000 X 70 ^ 55 = 63,636 B. T. U. for ventilation; then, 63,636 + 100,000 - - = 372 + square feet. EXAMPLES FOR PRACTICE 1. A schoolroom having 40 pupils is to be warmed and venti- lated when it is 10 degrees below zero. If the heat loss by conduction is 30,000 B. T. U. per hour, and the air supply is to be 40 cubic feet per minute per pupil, how many square feet of indirect radiation will be required? ANS. 273. 2. A contagious ward in a hospital has 10 beds, requiring 6,000 cubic feet of air each, per hour. The heat loss by conduction in zero weather is 80,000 B. T. U. How many square feet of indirect radia- tion will be required? ANS. 355. 3. The heat loss from a sitting room is 11,250 B. T. U. per hour in zero weather. How many square feet of indirect radiation will be required to warm it? ANS. 75. HEATING AND VENTILATION 77 IRON HE "AT /? Stacks and Casings. It has already been stated that a group of sections connected together is called a stack, and examples of these with their casings are shown in Figs. 50 and 51. The casings are usually made of galvanized iron, and are made up in sections by means of small bo*ks so that they may be taken apart in case it is necessary to make repairs. Large stacks are often enclosed in brick- work, the sides consisting of 8-inch walls, and the top being covered over with a layer of brick and mortar supported on light wrought-iron tee-bars. Blocks of asbestos are sometimes used for covering, instead of brick, the whole being covered over with plastic material of the same kind. Where a single stack supplies several flues or registers, the connections between these and the warm-air chamber are made in the same manner as already described for furnace heating. When galvanized-iron casings are used, the heater is supported by hangers from the floor above. Fig. 59 shows the method of hanging a heater from a wooden floor. If the floor is of fireproof construc- tion, the hangers may pass , u +u K L WRO'T IRON PIPE Up through the briCK- Fig 59 Method of Hanging a Heater below a Wooden work, and the ends be provided with nuts and large washers or plates ; or they may be clamped to the iron beams which carry the floor. Where brick casings are used, the heaters are supported upon pieces of pipe or light I-beams built into the walls. The warm-air space above the heater should never be less than 8 inches, while 12 inches is preferable for heaters of large size. The cold-air space may be an inch or two less; but if there is plenty of room, it is good practice to make it the same as the space above. Dampers. The general arrangement of a galvanized-iron casing and mixing damper is shown in Fig. 60. The cold-air duct is brought along the basement ceiling from the inlet window, and connects with the cold-air chamber beneath the heater. The entering air passes up between the sections, and rises through the register above, as shown by the arrows. When the mixing damper is in its lowest position, all air reaching the register must pass through the heater; but if the nnnnnmn 78 HEATING AND VENTILATION damper is raised to the position shown, part of the air will pass by without going through the heater, and the mixture entering through the register will be at a lower temperature than before. By changing FLOOR COLD A/R M/X/MG v* /HE AT > r 213 GALVAN/ZED IRON SLI&/NG DOOR CAS/NG Fig. 60. General Arrangement of a Galvanized-Iron Casing and Mixing Damper. Damper between Heater and Register. the position of the damper, the proportions of warm and cold air delivered to the room can be varied, thus regulating the temperature without diminishing to any great extent the quantity of air delivered. Fig. 61. Heater and Mixing Damper with Brick Casing. Damper between Heater and Register. The objection to this form of damper is that there is a tendency for the air to enter the room before it is thoroughly mixed; that is, a stream of warm air will rise through one half of the register while HEATING AND VENTILATION 79 cold air enters through the other. This is especially true if the con- nection between the damper and register is short. Fig. 61 shows a similar heater and mixing damper, with brick casing. Cold air is admitted to the large chamber below the heater, and rises through the sections to the^register as before. The action of the mixing damper is the same as already described. Several flues or registers may be connected with a stack of this form, each connection having, in addition to its mixing damper, an adjusting damper for regulating the flow of air to the different rooms. Another way of proportioning the air-flow in cases of this kind is to divide the hot-air chamber above the heater into sections, by means of galvanized-iron partitions, giving to each room its proper share of heating surface. If the cold-air supply is made sufficiently large, this arrangement is preferable to using adjusting dampers as J 7 > # ^ Fig. 62. Another Arrangement of Mixing Damper and Heater in Galvanized-Iron Casing. Heater between Damper and Register. described above. The partitions should be carried down the full depth of the heater between the sections, to secure the best results. The arrangement shown in Fig. 62 is somewhat different, and overcomes the objection noted in connection with Fig. 60, by sub- stituting another. The mixing damper in this case is placed at the other end of the heater. When it is in its highest position, all of the air must pass through the heater before reaching the register; but when partially lowered, a part of the air passes over the heater, and the result is a mixture of cold and warm air, in proportions depending upon the position of the damper. As the layer of warm air in this case is below the cold air, it tends to rise through it, and a more thorough mixture is obtained than is possible with the damper shown in Fig. 60. One quite serious objection, however, to this form of damper, is illustrated in Fig. 63. When the damper is nearly 80 HEATING AND VENTILATION Fig. 63. Showing Difficulty of Regulat- ing Temperature with Arrangement in Fig. 62. closed so that the greater part of the air enters above the heater, it has a tendency to fall between the sections, as shown by the arrows, and, becoming heated, rises again, so that it is impossible to deliver air to a room below a certain tem- perature. This peculiar action in- creases as the quantity of air admit- ted below the heater is diminished. When the inlet register is placed in the wall ai some distance above the floor, as in schoolhouse work, a thorough mixture of air can be obtained by plac- ing the heater so that the current of warm air will pass up the front of the flue and be discharged into the room through the lower part of the register. This is shown quite clearly in Fig. 64, where the cur- rent of warm air is represented by crooked arrows, and the cold air by straight ar- rows. The two currents pass up the flue separate- ly; but as soon as they are dis- charged through Fig. 64. Arrangement of Heater and Damper Causing Warm Air the register the to Enter Room through Lower Part of Register, thus Securing Thorough Mixing warm air tends to rise, and the cold air to fall, with the result of a more or less complete mixture, as shown. HEATING AND VENTILATION 81 It is often desirable to warm a room at times when ventilation is not necessary, as in the case of living rooms during the night, or for quick warming in the morning. A register and damper for air rotation should be provided Li this case. Fig. 65 shows an arrange- ment for this purpose. When the damper is in the position shown, air will be taken from the room above and be warmed over and over; but, by raising the damper, the supply will be taken from outsjde. Special care should be taken to make all mixing dampers tight against air-leakage, else their advantages will be lost. They should work easily and close tightly against flanges covered with felt. They may be operated from the rooms above by means of chains passing over COLD SUCT \ Fig. 65. Arrangement for Quick Heating without Ventilation. Damper Shuts off Fresh Air, and Air of Room Heated by Rotating Forth and Back through Register and Heater. guide-pulleys; special attachments should be provided for holding in any desired position. Warm=Air Flues. The required size of the warm-air flue between the heater and the register, depends first upon the difference in tem- perature between the air in the flue and that of the room, and second, upon the height of the flue. In dwelling-houses, where the con- ditions are practically constant, it is customary to allow 2 square inches area for each square foot of radiation when the room is on the first floor, and 1J square inches for the second and third floors. In the case of hospitals, where a greater volume of air is required, these figures may be increased to 3 square inches for the first floor wards, and 2 square inches for those on the upper floors. In schoolhouse work, it is more usual to calculate the size of flue from an assumed velocity of air-flow through it. This will vary greatly according to the outside temperature and the prevailing wind conditions. The following figures may be taken as average velocities 82 HEATING AND VENTILATION obtained in practice, and may be used as a basis for calculating the required flue areas for the different stories of a school building : 1st floor, 280 feet per minute. 2nd " , 340 " " 3rd " , 400 " These velocities will be increased somewhat in cold and windy weather and will be reduced when the atmosphere is mild and damp. Having assumed these velocities, and knowing the number of cubic feet of air to be delivered to the room per minute, we have only to divide this quanity by the assumed velocity, to obtain the required flue area in square feet. Example. A schoolroom on the second floor is to have an air-supply of 2,000 cubic feet per minute. What will be the required flue area? ANS. 2000 -=- 340 = 5.8 + sq. feet. The velocities would be higher in the coldest weather, and dampers should be placed in the flues for throttling the air-supply when nec- essary. Cold=Air Ducts. The cold-air ducts supplying heaters should be planned in a manner similar to that described for furnace heating. The air-inlet should be on the north or west side of the building; but this of course is not always possible. The method of having a large trunk line or duct with inlets on two or more sides of the building, should be carried out when possible. A cold-air room with large inlet windows, and ducts connecting with the heaters, makes a good arrangement for schoolhouse work. The inlet windows in this case should be provided with check-valves to prevent any outward flow of air. A detail of this arrangement is shown in Fig. 66. This consists of a boxing around the window, extending from the floor to the ceiling. The front is sloped as shown, and is closed from the ceiling to a point below the bottom of the window. The remainder is open, and covered with a wire netting of about J-inch mesh; to this are fastened flaps or checks of gossamer cloth about 6 inches in width. These are hemmed on both edges and a stout wire is run through the upper hem which is fastened to the netting by means of small copper or soft iron wire. The checks allow the air to flow inward but close when there is any tendency for the current to reverse. The area of the cold-air duct for any heater should be about three-fourths the total area of the warm-air ducts leading from^it. HEATING AND VENTILATION 83 If the duct is bf any considerable length or contains sharp bends, it should be made the full size of all the warm-air ducts. Adjusting dampers should be placed in the supply duct to each separate stack. If a trunk with two-inlets is used, each inlet should be of sufficient size to furnish the full amount of air required, and should be pro- vided with cloth checks for preventing an outward flow of air, as already described. The inlet windows should be provided with some form of damper or slide, outside of which should be placed a wire grating, backed by a netting of about f-inch mesh. Vent Flues. In dwelling-houses, vent flues are often omitted, and the frequent opening of doors and leakage are depended upon to carry away the im- pure air. A well- designed system of warming should provide some means for discharge ven- tilation, especially for bathrooms and toilet-rooms, and also for living rooms where lights are burned in the even- ing. Fireplaces are usually provided in the more important rooms of a well- built house, and these are made to serve as vent flues. In rooms having no fireplaces, special flues of tin or galvanized iron may be carried up in the partitions in the same manner as the warm-air flues. These should be gathered together in the attic, and connected with a brick flue running up beside the boiler or range chimney. Very fair results may be obtained by simply letting the flues open into an unfinished attic, and depending upon leakage through the roof to carry away the foul air. Fig. 66. Air-Inlet Provided with Check-Valves to Prevent Outward Flow of Air. 84 HEATING AND VENTILATION The sizes of flues may be made the reverse of the warm-air flues that is, 1J square inches area per square foot of indirect radiation for rooms on the first floor, and 2 square inches for those on the second. This is because the velocity of flow will depend upon the height of flue, and will therefore be greater from the first floor. The flow of air through the vents will be slow at best, unless some means is provided for warming the air in the flue to a temperature above that of the room with which it connects. The method of carrying up the outboard discharge beside a warm chimney is usually sufficient in dwelling-houses; but when it is desired to move larger quantities of air, a loop of steam pipe should be run inside the flue. This should be connected for drainage and air-venting as shown in Fig. 67. When vents are carried through the roof inde- pendently, some form of protecting hood should be provided for keeping out the snow and rain. A simple form is shown in Fig. 68. Flues carried outboard in this way should always be ex- . tended well above the ridges of adjacent roofs to prevent down drafts in windy weather. For schoolhouse work we may assume average velocities through the vent flues, as follows: Air Valve Ste Fig. 70 shows a section through a floor register, in which A rep- resents the valves, which may be turned in a vertical or hori- zontal position, thus opening Fig. 70. Section through a Floor Register. or closing the register; B is the iron border; C, the register box of tin or galvanized iron; and D, the warm-air pipe. Floor registers are usually set in cast-iron borders, one of which is shown in Fig. 71 ; while wall registers may be screwed directly to wooden borders or frames to correspond with the finish of the room. Wall registers should be provided with pull-cords for opening and closing from the floor? these are shown in Fig. 72. The plain lattice pattern shown in Fig. 73 is the best for schoolhouse- work, as it has a comparatively free opening for air-flow and is pleasing and sim- p 1 e in design. More elaborate patterns are used for fine dwelling- house work. Registers with shut-off valves are used for air- inlets, while the plain register faces without the valves are placed in the vent open- ings. The vent flues are usually gathered together in the attic, and a single damper may be used to shut off the whole number at once, Flat or round wire gratings of open pattern are often used in place of Fig. 71. Cast-Iron Border for a Floor Register. 88 HEATING AND VENTILATION register faces. The grill or solid part of a register face usually takes up about J of the area; hence in computing the size, we must allow for this by multiplying the required "net area" by 1.5, to obtain the "total" or "over-all" area. Example. Suppose we have a flue 10 inches in width and wish to use a register having a free area of 200 square inches. What will be the required height of the register? 200 X 1 . 5 = 300 square inches, which is the total area required ; then 300 -*- 10 = 30, which is the required height, and we should use a 10 by 30-inch register. When a register is spoken of as a 10 by Fig. 72. Wall Register with Pull Cords for Opening and Closing. Fig. 73. Plain Lattice Pattern Register, for Schoolhouse Work. Best 30-inch or a 10 by 20-inch, etc., the dimensions of the latticed opening are meant, and not the outside dimensions of the whole register. The free opening should have the same area as the flue with which it con- nects. In designing new work, one should provide himself with a trade catalogue, and use only standard sizes, as special patterns and sizes are costly. Fig. 74 sh^ws the method of placing gossamer check-valves back of the v< "* ?gister faces to prevent down drafts, the same as described : r fr r inlets. HEATING AND VENTILATION 89 Inlet registers in dwelling-house and similar work are placed either in the floor or in the baseboard; sometimes they are located under the windows, just above the baseboard. The object in view is to place them where the currents of air entering the room will not be objectionable to persons sitting near windows. A long, narrow floor-register placed close to the wall in front of a window, sends up a shallow current of warm air, which is not especially noticeable N GOSSAMER CHECKS WIRE NETTING Fig. 74. Method of Placing Gossamer Check- Valves back of Vent Register Face to Prevent Down Drafts. to one sitting near it. Inlet registers are preferably placed near outside walls, especially in large rooms. Vent registers should be placed in inside walls, near the floor. Pipe Connections. The two-pipe system with dry or sealed returns is used in indirect heating. The conditions to be met are practically the same as in direct heating, the only difference being that the radiators are at the basement ceiling instead of on the floors above. The exact method of making the pipe connections will depend somewhat upon existing conditions; but the general method shown in Fig. 75 may be used as a guide, with modifications to suit 90 HEATING AND VENTILATION any special case. The ends of all supply mains should be dripped, and the horizontal returns should be sealed if possible. Pipe Sizes. The tables already given for the proportioning of pipe sizes can be used for indirect systems. The following table has been computed for an efficiency of 640 B. T. U. per square foot of surface per hour, which corresponds to a condensation of f of a pound of steam. This is twice that allowed for direct radiation in Table DR/P WATER L/NE RETURN Fig. 75. General Method of Making Pipe and Radiator Connections, in Basement, in Indirect Heating. XVII; so that we can consider 1 square foot of indirect surface as equal to 2 of direct in computing pipe sizes. As the indirect heaters are placed in the basement, care must be taken that the bottom of the radiator does not come too near the water-line of the boiler, or the condensation will not flow back prop- erly; this distance, under ordinary conditions, should not be less than 2 feet. If much less than this, the pipes should be made extra large, so that there may be little or no drop in pressure between the boiler HEATING AND VENTILATION 91 TABLE XXV Indirect Radiating Surface Supplied by Pipes of Various Sizes SQUARE FEET OF INDIRECT RADIATION WHICH WILL BE SUPPLIED WITH i Pound Crop in 200 Feet 4 Pound Drop in 100 Feet i Pound Drop in 100 Feet 1 iii. 28 40 57 H 51 72 105 lj 67 95 170 2 185 262 375 2* 335 475 675 - 3 540 775 1, 105 3* 812 1,160 1,645 1, 140 1,625 2,310 5 2,030 2,900 4, 110 6 3,260 4,660 6, 600 7 4,830 6,900 9,810 8 6,800 9,720 13,860 and the heater. A drop in pressure of 1 pound would raise the water-line at the heater 2.4 feet. Fig. 76. General Form of Direct-Indirect Radiator. Fig. 77. Section through Radiator Shown in Fig. 76. Direct=Indirect Radiators. A direct-indirect radiator is similar in form to a direct radiator, and is placed in a room in the same 92 HEATING AND VENTILATION manner. Fig. 76 shows the general form of this type of radiator; and Fig. 77 shows a section through the same. The shape of the sections is such, that when in place, small flues are formed between them. Air is admitted through an opening in the outside wall; and, in passing upward through these flues, becomes heated before enter- ing the room. A switch-damper is placed in the duct at the base of the radiator, so that the air may be taken from the room itself instead ' f from out of doors, if so desired. This is shown rnore particularly in Fig. 76. Fig. 78 shows the wall box provided with louvre slats and netting, through which the air is drawn. A damper door is placed at either end of the radiator base ; and, if desired, when the cold-air supply is shut off by means of the register in the air-duct, the radia- tor can be converted into the ordinary type by opening both damper Fig. 78. Wall Box with Louvre Slats and Netting, doors, thus taking the air Direct-Indirect System. P , i ' i trom the room instead of from the outside. It is customary to increase the size of a direct- indirect radiator 30 per cent above that called for in the case of direct heating. CARE AND MANAGEMENT OF STEAM= HEATING BOILERS Special directions are usually supplied by the maker for each kind of boiler, or for those which are to be managed in any peculiar way. The following general directions apply to all makes, and may be used regardless of the type of boiler employed : Before starting the fire, see that the boiler contains sufficient water. The water-line should be at about the center of the gauge- glass. The smoke-pipe and chimney flue should be clean, and the draft good. Build the fire in the usual way, using a quality of coal which is best adapted to the heater. In operating the fire, keep the firepot HEATING AND VENTILATION 93 full of coal, and shake down and remove all ashes and cinders as often as the state of the fire requires it. Hot ashes or cinders must not be allowed to remain in the ashpit under the grate-bars, but must be removed at regular intervals to prevent burning oufrthe grate. To control the fire, see that the damper regulator is properly attached to the draft doors and the damper; then regulate the draft by weighting the automatic lever as may be required to obtain the necessary steam pressure for warming. Should the water in the boiler escape by means of a broken gauge-glass, or from any other cause, the fire should be dumped, and the boiler allowed to cool before adding cold water. An empty boiler should never be filled when hot. If the water gets low at any time, but still shows in the .gauge-glass, more water should be added by the means provided for this purpose. The safety-valve should be lifted occasionally to see that it is in working order. If the boiler is used in connection with a gravity system, it should be cleaned each year by filling with* pure water and emptying through the blow-off. If it should become foul or dirty, it can be thoroughly cleansed by adding a few pounds of caustic soda, and allowing it to stand for a day, and then emptying and thoroughly rinsing. During the summer months, it is recommended that the water be drawn off from the system, and that air-valves and safety-valves be opened to permit the heater to dry out and to remain so. Good results, however, are obtained by filling the heater full of water, driving off the air by boiling slowly, and allowing it to remain in this condition until needed in the fall. The water should then be drawn off and fresh water added. The heating surface of the boiler should be kept clean and free from ashes and soot by means of a brush made especially for this purpose. Should any of the rooms fail to heat, examine the steam valves in the radiators. If a two-pipe system, both valves at each radiator must be opened or closed at the same time, as required. See that the air-valves are in working condition. If the building is to be unoccupied in cold weather, draw all the water out of the system by opening the blow-off pipe at the boiler and all steam valves and air-valves at the radiators. 94 HEATING AND VENTILATION HOT= WATER HEATERS Types. Hot-water heaters differ from steam boilers principally in the omission of the reservoir or space for steam above the heating surface. The steam boiler might answer as a heater for hot water; but the large capacity left for the steam would tend to make its opera- tion slow and rather unsatisfactory, although the same type of boiler is sometimes used for both steam and hot water. The passages in a hot-water heater need not extend so directly from bottom to top as in a steam boiler, since the problem of provid- ing for the free liberation of the steam bubbles does not have to be con- sidered. In general, the heat from the furnace should strike the sur- faces in such a manner as to increase the natural circulation; this may be. accomplished to a cer- tain extent by arranging the heating surface so that a large proportion of the direct heat will be absorbed near the top of the heater. Practically the boilers for low-pressure steam and for hot water differ from each other very little as to the character of the heating surface, so that the methods already given for computing the size of grate surface, horse-power, etc., under the head of " Steam Boilers," can be Fig. 79. Richardson Sectional Hot-Water Heater. HEATING AND VENTILATION 95 used with satisfactory results in the case of hot- water heaters. It is sometimes stated that, owing to the greater difference in tem- perature between the furnace gases and the water in a hot-water heater, as compared^ with steam, the heating surface will be more efficient and a smaller heater can be used. While this is true to a certain extent, different authorities agree that this advantage is so small that no account should be taken of it, and the general propor- tions of the heater should be calculated in the same manner as for steam. Fig. 79 shows a form of hot-water heater made up of slabs or sections similar to the sectional steam boiler shown in Part I. The size can be increased in a similar manner, by adding more sections. In this case, however, the boiler is increased in width in- stead of in length. This has an advantage in the larger sizes, as a second fire door can be added, and all parts of the grate can be reached as well in the large sizes as in the small. Fig. 80 shows a different form of sec- tional boiler, in which the sections are placed one above an- other. These boilers are circular in form and well adapted to dwelling-houses and similar work. Fig. 81 shows another type of cast-iron heater which is not made in sections. The space between the outer and inner shells surround- ing the furnace is filled with water, and also the cross-pipes directly over the fire and the drum at the top. The supply to the radiators is taken off from the top of the heater, and the return connects at the lowest point. The ordinary horizontal and vertical tubular boilers, with various modifications, are used to a considerable extent for hot-water heating, Fig. 80. Invincible" Boiler, with Sections Superposed. Courtesy of American Radiator Co. 96 HEATING AND VENTILATION and are well adapted to this class of work, especially in the case of large buildings. Automatic regulators are often used for the purpose of main- taining a constant temperature of the water. They are constructed in different ways some depend upon the expansion of a metal pipe or rod at different temperatures, and others upon the vaporization and consequent pres- sure of certain volatile liquids. These means are usually employed to open small valves which admit water- pressure under rubber diaphragms; and these in turn are connected by means of chains with the draft doors of the furnace, and so regulate the draft as required to maintain an even temperature of the water in the heater. Fig. 82 shows one of the first kind. A is a metal rod placed in the flow pipe from the heater, and is so connected with the valve B that when the water reaches a certain temperature the expansion of the rod opens the valve and admits water from the street pressure through the pipes C and D into the chamber E. .The bottom of E consists of a rubber diaphragm, which is forced down by the water-pressure and carries with it the lever which operates the dampers as shown, and checks the fire. When the temperature of the water drops, the rod contracts and valve B closes, shutting off the pressure from the chamber . E. A spring is provided to throw the lever back to its original position, Fig. 81. Cast-Iron Heater Not Made in Sections. Water Fills Ci'oss-Pipes and Space between Outer and Inner Shells. HEATING AND VENTILATION 97 and the water above the diaphragm is forced out through the pet- cock G, which is kept slightly open all the time. ' DIRECT HOT=WATER HEATING A hot-water system is similar in construction and operation to one designed for steam, except that hot water flows through the pipes and radiators instead. The circulation through the pipes is produced solely by the dif- ference in weight of the water in the supply and return, due to the differ- e n c e in temperature. When water is heated it expands, and thus a given volume becomes lighter and tends to rise, and the cooler water flows in to take its place ; if the application of heat is kept up, the circulation thus produced is continuous. The velocity of flow de- pends upon the difference in temperature between the supply and return, and the height of the radiator above the boiler. The horizontal distance of the radiator from the boiler is also an important factor affecting the velocity of flow. This action is best shown by means of a diagram, as in Fig. 83. If a glass tube of the form shown in the figure is filled with water and held in a vertical position, no movement of the water will be noticed, because the two columns A and B are of the same weight, and there- fore in equilibrium. Now, if a lamp flame be held near the tube A, the small bubbles of steam which are formed will show the water to be in motion, with a current flowing in the direction indicated by the arrows. The reason for this is, that, as the water in A is heated, Fig. 82. Hot- Water Heater with Automatic Regu- lator Operated through Expansion and Con- traction of Metal Rod in Flow Pipe. 98 HEATING AND VENTILATION Fig. 83. Illustrating How the Heating of Water Causes Circulation. it expands and becomes lighter for a given volume, and is forced upward by the heavier water in B falling to the bottom of the tube. The heated water flows from A through the connecting tube at the top, into B, where it takes the place of the cooler water which is settling to the bottom. If, now, the lamp be replaced by a furnace, and the columns A and B be connected at the top by inserting a radiator, the illustration will assume the practical form as utilized in hot-water heating (see Fig. 84). The heat given off by the radiator always insures a difference in temperature between the columns of water in the supply and return pipes, so that as long as heat is supplied by the furnace the flow of water will continue. The greater the difference in temperature of the water in the two pipes, the greater the difference in weight, and con- sequently the faster the flow. The greater the height of the radiator above the heater, the more rapid will be the circulation, because the total difference in weight between the water in the supply and return risers will vary directly with their height. From the above it is evident that the rapidity of flow depends chiefly upon the temperature differ- ence between the supply and return, and upon the height of the radiator above the heater. Another factor which must be considered in long runs of horizontal pipe is the fric- tional resistance. Systems of Circulation. There are two distinct systems of cir- culation employed one depending on the difference in temperature of the water in the supply and return pipes, called gravity circulation*. \ X PANS/ ON TANK RAD/ATOR Fig. 84. Illustrating Simple Circula- tion in a Heating System. HEATING AND VENTILATION and another where a pump is used to force the water through the mains, called forced circulation. The former is used for dwellings and other buildings of ordinary size, and the latter for large buildings, and especially where there are long horizontal runs of pipe. For gravity circulation some form of sectional cast-iron boiler is commonly used, although wrought-iron tubular boilers may be employed if desired. In the case of forced circulation, a heater de- signed to warm the water by means of live or exhaust steam is often used. A centrifugal or rotary pump is best adapted to this pur- pose, and may be driven by an electric motor or a steam engine, as most convenient. Types of Radiating Surface. Cast-iron radiators and circulation coils are used for hot water as ^^m } - ^ well as for steam. Hot-water radiators differ from steam radiators principally in having a horizontal passage at the top as well as at the bottom. This construction is necessary in order to draw off the air which gathers at the top of each loop or section. Other- wise they are the same as steam radiators, and are well adapted for the circulation of steam, and in some respects are superior to the ordinary pattern of steam radiator. The form shown in Fig. 85 is made with an opening at the top for the entrance of water, and at the bottom for its discharge, thus insuring a supply of hot water at the top and of colder water at the bottom. Some hot-water radiators are made with a cross-partition so arranged that all water entering passes at once to the top, from which it may take any passage toward the outlet. Fig. 86 is the more common form of radiator, and is made with continuous passages at top and bottom, the hot water being supplied at one side and drawn off at the other. The action of gravity is depended upon for making the hot and lighter water pass to the top, and the colder water sink Fig. 85. Showing Construction of Radiator for Hot Water or Steam. Note Horizontal Pas- sage along Top. 100 HEATING AND VENTILATION to the bottom and flow off through the return. Hot-water radiators are usually tapped and plugged so that the pipe connections can be made either at the top or at the bottom. This is shown in Fig. 87. Wall radiators are adapted to hot-water as well as steam heating. Efficiency of Radiators. The efficiency of a hot-water radiator depends entirely upon the temperature at which the water is circu- lated. The best practical results are obtained with the water leaving the boiler at a maximum temperature of about 180 degrees in zero weather and returning at about 160 degrees; this gives an average Fig. 86. Common Form of Hot-Water Radiator. Circulation Fig. 87. End Elevation of Produced Wholly through Action of Gravity, Hot Water Rising to Top. Radiator Showing Taps at Top and Bottom for Pipe Connections. temperature of 170 degrees in the radiators. Variations may be made, however, to suit the existing conditions of outside temperature. We have seen that an average cast-iron radiator gives off about 1.7 B.T.U. per hour per square foot of surface per degree difference in tempera- ture between the radiator and the surrounding air, when working under ordinary conditions; and this holds true whether it is filled with steam or water. If we assume an average temperature of 170 degrees for the water, then the difference in temperature between the radiator and the air will be 170 70 = 100 degrees; and this multiplied by 1 .7 = HEATING AND VENTILATION 101 170, which may be taken as the efficiency of a hot-water radiator under the above average conditions. This calls for a water radiator about 1 . 5 times as large as a steam radiator to heat a given room under the same conditions. This is common practice although some engineers multiply by the factor 1 . 6, which allows for a lower temperature of the water. Water leaving the boiler at 170 degrees should return at about 150; the drop in temperature should not ordinarily exceed 20 degrees. Systems of Piping. A system of hot-water heating should pro- duce a perfect circulation of water from the heater to the radiating Fig. 88. System of Piping Usually Employed for Hot-Water Heating. surface, and thence back to the heater through the returns. The system of piping usually employed for hot-water heating is shown in Fig. 88. In this arrangement the main and branches have an inclina- tion upward from the heater; the returns are parallel to the mains, and have an inclination downward toward the heater, connecting with it at the lowest point. The flow pipes or risers are taken from the tops of the mains, and may supply one or more radiators as required. The return risers or drops are connected with the return mains in a similar manner. In this system great care must be taken to produce a nearly equal resistance to flow in all of the branches, so that each radiator may receive its full supply of water. It will always 102 HEATING AND VENTILATION be found that the principal current of heated water will take the path of least resistance, and that a small obstruction or irregularity in the piping is sufficient to interfere greatly with the amount of heat received in the different parts of the same system. Some engineers prefer to carry a single supply main around the building, of sufficient size to supply all the radiators, bringing back a single return of the same size. Practice has shown that in general it is not well to use pipes over 8 or 10 inches in diameter; if larger pipes are required, it is better to run two or more branches. The boiler, if possible, should be centrally located, and branches carried to differ- ent parts of the building. This insures a more even circulation than if all the radiators are supplied from a single long main, in which case the circulation is liable to be sluggish at the farther end. The arrange- ment shown in Fig. 89 is similar Fig. 89. System of Hot- Water Piping Especially Adapted to Apartment Buildings where Each Flat Has a Separate Heater. to the circuit system for steam, except that the radiators have two connections instead of one. This method is especially adapted to apartment houses, where each flat has its separate heater, as it eliminates a separate return main, and thus reduces, by practically one-half, the amount of piping in the basement. The supply risers are taken from the top of the main; while the returns should con- nect into the side a short distance beyond, and in a direction away from the boiler. When this system is used, it is necessary to enlarge the radiators slightly as the distance from the boiler increases. In flats of eight or ten rooms, the size of the last radiator may be increased from 10 to 15 per cent, and the intermediate ones proper- DIRECT-INDIRECT SYSTEM OF WARMING, SHOWING ADJUSTABLE DAMPER. American Radiator Company. HEATING AND VENTILATION 103 tionally, at the same time keeping the main of a large and uniform size for the entire circuit. Overhead Distribution. This system of piping is shown in Fig. 90. A single riser is carried directly to the expansion tank, from which branches are 'taken to supply the various drops to which the radiators are connected. An important advantage in connection with this system is that the air rises at once to thejexpansion tank, and escapes through the vent, so that air-valves are not required on the radiators. xpa.tas-ioT-1 Tank Fig. 90. "Overhead" Distribution System of Hot- Water Piping. At the same time, it has the disadvantage that the water in the tank is under less pressure than in the heater; hence it will boil at a lower temperature. No trouble will be experienced from this, how- ever, unless the temperature of the water is raised above 212 degrees. Expansion Tank. Every system for hot- water heating should be connected with an expansion tank placed at a point somewhat above the highest radiator. The tank must in every case be connected to a line of piping which cannot by any possible means be shut off from the boiler When water is heated, it expands a certain amount, 104 HEATING AND VENTILATION OVERFLOW depending upon the temperature to which it is raised; and a tank or reservoir should always be provided to care for this increase in volume. Expansion tanks are usually made of heavy galvanized iron of one of the forms shown in Figs. 91 and 92, the latter form being used where the headroom is limited. The connection from the heating system enters the bottom of the tank, and an open vent pipe is taken from the top. An overflow connected with a sink or drain-pipe should be provided. Connections should be made with the water supply both at the boiler and at the expansion tank, the former to be used when first filling the system, as by this means all air is driven from the bot- tom upward and is discharged through the vent at the expansion Fig. 91. A Common Form of Galvanized- f QT1 T,- Waf^r fliat i.r * irrj 100 ft. Run 200 ft. Run 300 ft. Run 400 ft. Run 500 ft, Run 600 ft. Run 700 ft. Run 800 ft. Run 1,000 ft. Run 1 in. 30 u* 60 50 ir 100 75 50 2 ' 200 150 125 100 75 2*' 350 250 200 175 150 125 3 ' 550 400 300 275 250 225 200 175 150 3*' 850 600 450 400 350 325 300 250 225 4 ' 1,200 850 700 600 525 475 450 400 350 5 ' 1,400 1,150 1,000 700 850 775 725 650 6 ' 1,600 1,400 1,300 1,200 1,150 1,000 7 ' 1,706 1,600 1,500 These quantities have been calculated on a basis of 10 feet difference in elevation between the center of the heater and the radiators, and a differ- ence in temperature of 17 degrees between the supply and the return. TABLE XXVII Radiating Surface on Different Floors Supplied by Pipes of Different Sizes SIZE OF SQUARE FEET OF RADIATING SURFACE 1st Story 2d Story 3d Story 4th Story 5th Story 6th Story 1 in. 30 55 65 75 85 95 1M - 60 90 110 125 140 160 \y 2 100 140 165 185 210 240 2 200 275 375 425 500 21/2 350 475 3 550 sy 2 850 Table XXVI gives the number of square feet of direct radiation which different sizes of mains and branches will supply for varying lengths of run. Table X*XVI may be used for all horizontal mains. For vertical risers or drops, Table XXVII may be used. This has been com- 112 HEATING AND VENTILATION puted for the same difference in temperature as in the case of Table XXVI (17 degrees), and gives the square feet of surface which dif- ferent sizes of pipe will supply on the different floors of a building, assuming the height of the stories to be 10 feet. Where a single riser is carried to the top of a building to supply the radiators on the floors below, by drop pipes, we must first get what is called the average elevation of the system before taking its size from the table. This may be illustrated by means of a diagram (see Fig. 105). In A we have a riser carried to the third story, and from there a drop brought down to supply a radiator on the first floor. The elevation available for producing a flow in the riser is only 10 feet, the same as though it extended only to the radiator. The water in the two pipes above the radiator is practically at the same temperature, and therefore in equilibrium, and has no effect on the flow of the water in the riser. (Actually there would be some radiation from the pipes, and the return, above the radiator, would be slightly cooler, but for purposes of illustration this may be neglected). If the radiator was on the second floor the elevation of the system would be 20 feet (see #); and on the third floor, 30 feet; and so on. The distance which the pipe is carried above the first radiator which it supplies has but little effect in producing a flow, especially if covered, as it should be in practice. Having seen that the flow in the main riser depends upon the elevation of the radiators, it is easy to see that the way in which it is distributed on the different floors must be con- sidered. For example, in B, Fig. 105, there will be a more rapid flow through the riser with the radiators as shown, than there would be if they were reversed and the largest one were placed upon the first floor. We get the average elevation of the system by multiplying the square feet of radiation on each floor by the elevation above the heater, then adding these products together and dividing the same by the total radiation in the whole system. In the case shown in By the average elevation of the system would be (100 X 30) + (50 X 20) + (25 X 10) _ 100 + 50 + 25 and we must proportion the main riser the same as though the whole radiation were on the second floor. Looking in Table XXVII, we find, for the second story, that a IJ-inch pipe will supply 140 square HEATING AND VENTILATION 113 feet; and a 2-inch pipe, 275 feet. Probably a H-inch pipe would be sufficient. Although the height of stories varies in different buildings, 10 feet will be found sufficiently accurate for ordinary practice. + INDIRECT HOT=WATER HEATING This is used under the same conditions as indirect steam, and the heaters used are similar to those already described. Special 100 50 A B Fig. 105. Diagram to Illustrate Finding of Average Elevation of Heating System. attention is given to the form of the sections, in order that there may be an even distribution of water through all parts of them. As the stacks are placed in the basement of a building, and only a short distance above the boiler, extra large pipes must be used to secure a proper circulation, for the head producing flow is small. The stack 114 HEATING AND VENTILATION casings, cold-air arid warm-air pipes, and registers are the same as in steam heating. Types of Radiators. The radiators for indirect hot-water heating are of the same general form as those used for steam. Those shown in Figs. 52, 53, 56, 106, and 107 are common patterns. The drum pin, Fig. 106, is an excellent form, as the method of making the connections insures a uniform distribution of water through the stack. Fig. 107 shows a radiator of good form for water circulation, and also of good depth, which is a necessary point in the design of hot- water radiators. They should be not less than 12 or 15 inches deep for good results. Box coils of the form given for steam may also be Fig. 106. "Drum Pin" Indirect Hot-Water Radiator. used, provided the connections for supply and return are made of good size. Size of Stacks. As indirect hot-water heaters are used princi- pally in the warming of dwelling-houses, and in combination with direct radiation, the easiest method is to compute the surfaces required for direct radiation, and multiply these results by 1 .5 for pin radiators of good depth. For other forms the factor should vary from 1 . 5 to 2, depending upon the depth and proportion of free area for air- flow between the sections. If it is desired to calculate the required surface directly by the thermal unit method, we may allow an efficiency of from 360 to 400 for good types in zero weather. HEATING AND VENTILATION 115 In schoolhouse and hospital work, where larger volumes of air are warmed to lower temperatures, an efficiency as high as 500 B. T. U. may be allowed for radiators of good form. Flues and Casings. For cleanliness, as well as for obtaining the best results, indirect stacks should be hung at one side of the register or flue receiving the warm air, and the cold-air duct should enter beneath the heater at the other side. A space of at least 10 inches, and preferably 12, should be allowed for the warm air above the stack. The top of the casing should pitch upward toward the warm-air outlet at least an inch in its length. A space of from 8 to 10 inches should be allowed for cold air below the stack. As the amount of air warmed per square foot of heating surface is less than in the case of steam, we may make the flues somewhat smaller as compared with the size of heater. The following p r o - portions may be used under usual conditions for dwelling-houses: 1J square inches per square foot of radia- tion for the first floor, 1J square inches for the second floor, and 1J square inches for the cold-air duct. Pipe Connections. In indirect hot-water work, it is not desirable to supply more than 80 to 100 square feet of radiation from a single connection. When the requirements call for larger stacks, they should be divided into two or more groups according to size. It is customary to carry up the main from the boiler to a point near the basement ceiling, where it is air-vented through a small pipe leading to the expansion tank. The various branches should grade downward and connect with the tops of the stacks. In this way, all air, both from the boiler and from the stacks, will find its way to the highest point in the main, and be carried off automatically. As an additional precaution, a pet-cock air-valve should be placed in the last section of each stack, and brought out through the casing by means of a short pipe. Fig. 107. Indirect Hot- Water Radiator. 116 HEATING AND VENTILATION TABLE XXVIII Radiating Surface Supplied by Pipes of Various Sizes Indirect Hot- Water System DIAMETER SQUARE FEET OP RADIATING SURFACE PIPE 100 Ft. Run 200 Ft. Run 300 Ft. Run 400 Ft. Run 1 in. 15 H 30 25 1* 50 40 25 2 100 75 60 50 2* 175 125 100 90 3 275 200 150 140 3* 425 300 225 200 4 600 425 350 300 5 . 700 575 500 6 800 7 1,200 Some engineers make a practice of carrying the main to the ceiling of the first story, and then dropping to the basement before branching to the stacks, the idea being to accelerate the flow of water through the main, which is liable to be sluggish on account of the small difference in elevation between the boiler and stacks. If the return leg of the loop is left uncovered, there will be a slight drop in temperature, tending to produce this result; but in any case it will be exceedingly small. With supply and return mains of suitable size and properly graded, there should be no difficulty in securing a good circulation in basements of average height. Pipe Sizes. As the difference in elevation between the stacks and the heater is necessarily small, the pipes should be of ample size to offset the slow velocity of flow through them. The sizes mentioned in Table XXVIII, for runs up to 400 feet, will be found to supply ample radiating surface for ordinary conditions. Some engineers make a practice of using somewhat smaller pipes, but the larger sizes will in general be found more satisfactory. CARE AND MANAGEMENT OF HOT=WATER HEATERS The directions given for the care of steam-heating boilers apply in a general way to hot-water heaters, as to the methods of caring for the fires and for cleaning and filling the heater. Only the special points of difference need be considered. Before building the fire, all the pipes and radiators must be full of water, and the expansion tank HEATING AND VENTILATION 117 should be partially filled as indicated by the gauge-glass. Should the water in any of the radiators fail to circulate, see that the valves are wide open and that the radiator is free from air. Water must always be added at the expansion tank when for any reason it is drawn from the systeih. The required temperature of the water will depend upon the outside conditions, and only enough fire should be carried to keep the rooms comfortably warm. Ther- mometers should be placed in the flow and return pipes near the heater, as a guide. Special forms are made for this purpose, in which the bulb is im- mersed in a bath of oil or mercury (see Fig. 108). FORCED HOT-WATER LATION CIRCU- While the gravity system of hot- water heating is well adapted to buildings of small and medium size, there is a limit to which it can be car- ried economically. This is due to the slow movement of the water, which calls for pipes of excessive size. To overcome this difficulty, pumps are used to force the water through the mains at a comparatively high velocity. The water may be heated in a boiler in the same manner as for gravity circulation, or exhaust steam may be utilized in a feed-water heater ! . p, , of large size. Sometimes part of the heat is derived from an economizer placed in the smoke passage from the boilers. Systems of Piping. The mains for^forced circulation are usually run in one of two ways. In the two-pipe system, shown in Fig. 109, the supply and return are carried side by side, the former reducing in size, and the latter increasing as the branches are taken off. mine Temperature of Water. 118 HEATING~AND VENTILATION The flow through the risers is produced by the difference in pressure in the supply and return mains; and as this is greatest nearest the pump, it is necessary to place throttle-valves in the risers to prevent short-circuiting and to secure an even distribution through all parts of the system. Fig. 110 shows the single-pipe or circuit system. This is similar to the one already described for gravity circulation, except that it can be used on a much larger scale. A single main is carried entirely around the building in this case, the ends being connected with the suction and discharge of the pump as shown. As the pressure or head in the main drops constantly throughout the circuit, from the discharge of the pump back to the suction, it is Fig. 109. "Two-Pipe" System for Forced Hot- Water Circulation. evident that if a supply riser be taken off at any point, and the return be connected into the main a short distance along the line, there will be a sufficient difference in pressure between the two points to produce a circulation through the two risers and the connecting radiators, A distance of 8 or 10 feet between the connections is usually ample to produce the necessary circulation, and even less if the supply is taken from the top of the main and the return connected into the side. Sizes of Mains and Branches. As the velocity of flow is inde- pendent of the temperature and elevation when a pump is used, it is necessary to consider only the volume of water to be moved and the, length of run. HEATING AND VENTILATION 119 The volume is found by the equation 500 T' in which Q = Gallons of water required per minute; R Square feet'of radiating surface to be supplied; E = Efficiency of radiating surface in B. T. U. per sq. foot per hour; T = Drop in temperature of the water in passing through the heating system. In systems of this kind, where the circulation is comparatively rapid, it is customary to assume a drop in temperature of 30 to 40, between the supply and return. Having determined the gallons of water to be moved, the required size of main can be found by assuming the velocity of flow, which for pipes from 5 to 8 inches in diameter may be taken at 400 to 500 Fig. 110. "Single-Pipe" or "Circuit" System for Forced Hot- Water Circulation. feet per minute. A velocity as high as 600 feet is sometimes allowed for pipes of large size, while the velocity in those of smaller diameter should be proportionally reduced to 250 or 300 feet for a 3-inch pipe. The next step is to find the pressure or head necessary to force the water through the main at the given velocity. This in general should not exceed 50 or 60 feet, and much better pump efficiencies will be obtained with heads not exceeding 35 or 40 feet. As the water in a heating system is in a state of equilibrium, the only power necessary to produce a circulation is that required to overcome the friction in the pipes and radiators; and, as the area of the passageways through the latter is usually large in comparison with the former, it is customary to consider only the head necessary to force the water through the mains, taking into consideration the additional friction produced by valves and fittings. 120 HEATING AND VENTILATION Each long-turn elbow may be taken as adding about 4 feet to the length of pipe; a short-turn fitting, about 9 feet; 6-inch and 4-inch swing check-valves, 50 feet and 25 feet, respectively; and 6-inch and 4-inch globe check-valves, 200 feet and 130 feet, respec- tively. Table XXIX is prepared especially for determining the size of mains for different conditions, and is used as follows : Example. Suppose that a heating system requires the circulation of 480 gallons of water per minute through a circuit main 600 feet in length. The pipe contains 12 long-turn elbows and 1 swing check-valve. What diameter of main should be used ? Assuming a velocity of 480 feet per minute as a trial velocity, we follow along the line corresponding to that velocity, and find that a 5-inch pipe will deliver the required volume of water under a head of 4.9 feet for each 100 feet length of run. The actual length of the main, including the equivalent of the fittings as additional length, is 600+ (12X9) + 50 -758 feet; hence the total head required is 4.9 X 7.58 = 37 feet. As both the assumed velocity and the necessary head come within practicable limits, this is the size of pipe which would probably be used. If it were desired to reduce the power for running the pump, the size of main could be increased. That is, Table XXIX shows that a 6-inch pipe would deliver the same volume of water with a friction head of only about 2 feet per 100 feet in length, or a total head of 2 X 7 .58 = 15 feet. The risers in the circuit system are usually made the same size as for gravity work, With double mains, as shown in Fig. 109, they may be somewhat smaller, a reduction of one size for diameters over 1J inches being common The branches connecting the risers with the mains may be pro- portioned from the combined areas of the risers. When the branches are of considerable size, the diameter may be computed from the available head and volume of water to be moved. Pumps. Centrifugal pumps are usually employed in connection with forced hot-water circulation, in preference to pumps of the piston or plunger type. They are simple in construction, having no valves, produce a continuous flow of water, and, for the low heads HEATING AND VENTILATION 121 TABLE XXIX Capacity in Gallons per Minute Discharged at Velocities of 300 to 540 Feet per Minute Also Friction Head in Feet, per 100 Feet Length of Pipe DIAMETER OF PIPE 8-lNCH Friction H CO mimiilatino % in thp Condensation, au radiator or coil, passes into the chamber E, through the inlet C, rises in the chamber, and seals the space between the seal-shell A and the sleeve of the bonnet D. The differential pressure thus created causes the seal A to rise, lifting the end of the central tube off the seat, thus opening a clear passageway for the ejection of the water of condensation. Fig. 130. Showing Method of Draining Bottoms of Risers or Ends HEATING AND VENTILATION 143 When all the water of condensation has been drawn out of the radiator, the seal and tube are reseated by gravity, thus closing the port K, preventing waste or loss of steam ; and the pressure is equal- ized above and below the seal because of the absence of water. This action is practically instantaneous. When the condensation is small in quantity, the discharge is intermittent and rapid. The space between the seal A and the sleeve of the bonnet D, and the annular space between the central tube G and the spindle B, Fig. 131. Water-Seal Motor. form a passageway through which the air is continually withdrawn by the vacuum pump or other draining apparatus. The action outlined continues as long as water is present. No adjustment whatever is' necessary; the motor is entirely auto- matic. One special advantage claimed for this system is that the amount of steam admitted to the radiators may be regulated to suit the require- ments of outside temperature; and is possible without water- 144 HEATING AND VENTILATION HEATING AND VENTILATION 145 logging or hammering. This may be done at will by closing down on the inlet supply to the desired degree. The result is the admission of a smaller amount of steam to the radiator than it is calculated to condense normally. >The condensation is removed as fast as formed, by the opening of the thermostatic valve. The general application of this system to exhaust heating is shown in Fig. 132. Exhaust steam is brought from the engine as shown; one branch is connected with a feed-water heater, while the other is carried upward and through a grease extractor, where it branches again, one line leading outboard through a back-pressure valve and the other connecting with the heating main. A live steam connection is made through a reducing valve, as in the ordinary system. Valved connections are made with the coils and radiators in the usual manner; but the return valves are replaced by the special thermostatic valves described above. The main return is brought down to a vacuum pump which dis- charges into a return tank, where the air is separated from the water and passes off through the vapor pipe at the top. The condensation then flows into the feed-water heater, from which it is automatically pumped back into the boilers. The cold-water feed supply is con- nected with the return tank, and a small cold.- water jet is connected into the suction at the vacuum pump for increasing the vacuum in the heating system by the condensation of steam at this point. Paul System. In this system the suction is connected with the air-valves instead of the returns, and the vacuum is produced by means of a steam ejector instead of a pump. The returns are carried back to a receiving tank, and pumped back to the boiler in the usual manner. The ejector in this case is called the exhauster. Fig. 133 shows the general method of making the pipe connections with the radiators in this system; and Fig. 134, the details of connec- tion at the exhauster. A A are the returns from the air-valves, and connect with the exhausters as shown. Live steam is admitted in small quantities through the valves B B ; and the mixture of air and steam is discharged outboard through the pipe C. D D are gauges showing the pressure in the system; and E E are check-valves. The advantage of this system depends principally upon the quick removal of air from the various radiators and pipes, which constitutes the principal obstruction 146 HEATING AND VENTILATION to circulation ; the inductive action in many cases is sufficient to cause the system to operate somewhat below atmospheric pressure. Where exhaust steam is used for heating, the radiators should PAUL SYSTEM Of HEATIN6 Fig. 133. Shoeing General Method of Making Pipe and Radiator Connections in Paul System. be somewhat increased in size, owing to the lower temperature of the steam. It is common practice to add from 20 to 30 per cent to the sizes required for low-pressure live steam. HEATING AND VENTILATION 147 FORCED BLAST In a system of forced circulation by means of a fan or blower the action is positive and practically constant under all usual con- ditions of outside temperature and wind action.. This gives it a decided advantage o>ver natural or gravity methods, which are af- A A Fig. 134. Details of Connections at Exhauster, Paul System. fected to a greater or less degree by changes in wind-pressure, and makes it especially adapted to the ventilation and warming of large buildings such as shops, factories, schools, churches, halls, theaters, etc., where large and definite air-quantities are required. Exhaust Method. This consists in drawing the air out of a building, and providing for the heat thus carried away by placing 148 HEATING AND VENTILATION steam coils under windows or in other positions where the inward leakage is supposed to be the greatest. When this method is used, a partial vacuum is created within the building or room, and all currents and leaks are inward ; there is nothing to govern definitely the quality and place of introduction of the air, and it is difficult to provide suit- able means for warming it. Plenum Method. In this case^the air is forced into the building, and its quality, temperature, and point of admission are completely under control. All spaces are filled with air under a slight pressure, and the leakage is outward, thus preventing the drawing of foul air into the room from any outside source. But above all, ample oppor- tunity is given for properly warming the air by means of heaters, either in direct connection with the fan or in separate passages leading to the various rooms.- Form of Heating Surface. The besttype of heater for any particular case will depend upon the volume and final temperature of the air, the steam pressure, and the available space. When the air is to be heated to a high temperature for both warming and venti- lating a building, as in the case of a shop or mill, heaters of the general form shown in Figs. 135, 136, and 137 are used. These may also be adapted to all classes of work by varying the proportions as required. They can be made shallow and of large superficial area, for the com- paratively low temperatures used in purely ventilating work; or deeper, with less height and breadth, as higher temperatures are required. Fig, 135 shows in section a heater of this type, and illustrates the circulation of steam through it. It consists of sectional cast-iron bases with loops of wrought-iron pipe_ connected as shown. The steam enters the upper part of the bases or headers, and passes up one side of the loops, then across the top and down on the other side, where the condensation is taken off through" the return drip, which is separated from the inlet by a partition. These heaters are made up in sections of 2 and 4 rows of pipes each. The height varies from 3^ to 9 feet, and. the width. from 3 feet to 7 feet in the standard sizes. They are usually made up of 1-inch pipe, although IJ-inch is commonly used in the larger sizes. Fig. 136 shows another form; in this case all the loops are made of practically the same length by the special form of construction shown. This is claimed to prevent the short- HEATING AND VENTILATION 149 circuiting of steam through the shorter loops, which causes the outer pipes to remain cold. This form of heater is usually encased in a Fig. 135. Showing Circulation of Steam in Large Coil-Pipe Radiator for Heating Mills, Shops, etc. sheet-steel housing as shown in Fig. 137, but may be supported on 3 foundation between brick walls if desired. 150 HEATING AND VENTILATION Fig. 138 shows a special form of heater particularly adapted to ventilating work where the air does not have to be raised above 70 or 80 degrees. It is made up of 1-inch wrought-iron pipe connected with supply and return headers; each section contains 14 pipes, and they are usually made up in groups of 5 sections each. These coils are supported upon tee-irons resting upon a brick foundation. Heat- HEATING AND VENTILATION 151 ers of this form are usually made to extend across the side of a room with brick walls at the sides, instead of being encased in steel housings. Fig. 139 shows a front view of a cast-iron sectional heater for use under the same conditions as the pipe heaters already described. This heater is macteoip of several banks of sections, like the one shown in the cut, and enclosed in a steel-plate casing. Cast-iron indirect radiators of the pin type are well adapted for use in connection with mechanical ventilation, and also for heating Fig. 137. Large Coil-Pipe Radiator Encased in Sheet-Steel Housing. where the air-volume is large and the temperature not too high, as in churches and halls. They make a convenient form of heater for schoolhouse and similar work, for, being shallow, they can be sup- ported upon I-beams at such an elevation that the condensation will be returned to the boilers by gravity. In the case of vertical pipe heaters, the bases are below the water- line of the boilers, and the condensation must be returned by the use of pumps and traps. 152 HEATING AND VENTILATION Efficiency of Pipe Heaters. The efficiency of the heaters used in connection with forced blast varies greatly, depending upon the temperature of the entering air, its velocity between the pipes, the temperature to which it is raised, and the steam pressure carried in the heater. The general method in which the heater is made up is also an important factor. In designing a heater of this kind, care must be taken that the free area between the pipes is not contracted to such an extent that an excessive velocity will be required to pass the given quantity of CE/L/NG UNE A/R VALVE PLAN AT SUPPLY END FRONT V/EW S/0 V/EW Fig. 138. Heater Especially Adapted to Ventilation where Air does not Have to be Heated above 70 to 80 degrees F. air through it. In ordinary work it is customary to assume a velocity of 800 to 1,000 feet per minute; higher velocities call for a greater pressure on the fan, which is not desirable in ventilating work. In the heaters shown, about .4 of the total area is free for the passage of air; that is, a heater 5 feet wide and 6 feet high would have a total area of 5 X 6 = 30 square feet, and a free area between the pipes of 30 X .4 = 12 square feet. The depth or number of rows of pipe does not affect the free area, although the friction is increased and additional work is thrown upon the fan. The efficiency in any HEATING AND VENTILATION 153 given heater will be increased by increasing the velocity of the air through it; but the final temperature will be diminished; that is, a larger quantity of air will be heated to a lower temperature in the second case, and, while the total heat given off is greater, the air- quantity increases more rapidly than the heat-quantity, which causes a drop in temperature. Increasing the number of rows of pipe in a heater, with a con- stant air-quantity, increases the final temperature of the air, but diminishes the efficiency of the heater, because the average difference in temperature between the air and the steam is less. Increasing the steam pressure in the heater (and consequently its temperature) increases both the final temperature of the air and the efficiency of the heater. Table XXX has been prepared from different tests, and may be used as a guide in computing probable results under ordinary working con- ditions. In this table it is assumed that the air enters the heater at a temperature of zero and passes between the pipes with a velocity of 800 feet per minute. Column 1 gives the number of rows of pipe in the heater, ranging from 4 to 20 rows; and columns 2, 3, and 4, show the final tempera- ture to which the entering air will be raised from zero under various pressures. Under 5 pounds pressure, for example, the rise in tem- perature ranges from 30 to 140 degrees; under 20 pounds, 35 to 150 degrees; and under 60 pounds, 45 to 170 degrees. Columns 5, 6, and 7 give approximately the corresponding efficiency of the heater. For example, air passing through a heater 10 pipes deep and carrying 20 pounds pressure, will be raised to a temperature of 90 degrees, and the heater will have an efficiency of 1,650 B. T. U. per square foot of surface per hour. Fig. 139. Front View of Cast-Iron Sectional Heater. The Banks of Sections are En- closed in a Steel- Plate Casing. 154 HEATING AND VENTILATION TABLE XXX Data Concerning Pipe Heaters Temperature of entering air, zero. Velocity of air between the pipes, 800 feet per minute. TEMPERATURE TO WHICH AIR WILL BE RAISED FROM ZERO EFFICIENCY OF HEATING SURFACE iNB.T.U., PER SQUARE FOOT PER HOUR Rows OF PIPE DEEP Steam Pressure in Heater Steam Pressure in Heater 5 Ibs. 20 Ibs. 60 Ibs. 5 Ibs. 20 Ibs. 60 Ibs. 4 30 35 45 1,600 ,800 2,000 6 50 55 65 1,600 ,800 2,000 8 65 70 85 1,500 ,650 1,850 10 80 90 105 ,500 ,650 1,850 12 95 105 125 ,500 ,650 1,850 14 105 120 140 ,400 ,500 1,700 16 120 130 150 ,400 ,500 1,700 18 130 140 160 ,300 ,400 1,600 20 140 150 170 ,300 ,400 1,600 For a velocity of 1,000 feet, multiply the temperatures given in the table by .9, and the efficiencies by 1.1. Example. How many square feet of radiation will be required to raise 600,000 cubic feet of air per hour from zero to 80 degrees, with a velocity through the heater of 800 feet per minute and a steam pressure of 5 pounds? What must be the total area of the heater front, and how many rows of pipes must it have? Referring back to the formula for heat required for ventilation, we have 600,000 X 80 . 55 = 872,727 B. T. U. required. Referring to Table XXX, we find that for the above conditions a heater 10 pipes deep is required, and that an efficiency of 1,500 B. T. U. will be obtained. Then 872,727 1,500 = 582 square feet of surface required, which may be taken as 600 in round numbers. 600,000 , . , . . . , 10,000 = 10,000 cubic feet of air per minute; and =12.5 60 oOO square feet of free area required through the heater. If we assume .4 of the total heater front to be free for the passage of air, then ~ = 31 square feet, the total area required. HEATING AND VENTILATION 155 For convenience in estimating the approximate dimensions of a heater, Table XXXI is given. The standard heaters made by dif- ferent manufacturers vary somewhat, but the dimensions given in the table represent average practice. Column 3 gives the square feet of heating surf ace In a single row of pipes of the dimensions given in columns 1 and 2; and column 4 gives the free area between the pipes. TABLE XXXI Dimensions of Heaters WIDTH OP SECTION HEIGHT op PIPES SQUARE FEET OF SURFACE FREE AREA THROUGH HEATER IN SQ. FT. 3 feet 3 feet 6 inches 20 4.2 3 " 4 " " 22 4.8 3 " 4 " 6 " 25 5.4 3 " 5 " " 28 6.0 4 " 4 "6 " 34 7.2 4 " 5 " " 38 8.0 4 " 5 " 6 " 42 8.8 4 " 6 " " 45 9.6 5 " 5 " 6 " 52 11.0 5 " 6 " " 57 12.0 5 " 6 " 6 " 62 13.0 5 " 7 . " " 67 14.0 6 " 6 " 6 " 75 15.6 6 " 7 " " 81 16.8 6 " 7 " 6 87 18.0 6 " 8 " " 92 19.2 7 " 7 " 6 " 98 21.0 7 " 8 " " 108 22.4 7 " 8 " 6 " 109 23.8 7 " 9 " " 116 25.2 In calculating the total height of the heater, add 1 foot for the base. These sections are made up of 1-inch pipe, except the last or 7-foot sections, which are made of IJ-inch pipe. Using this table in connection with the example just given, we should look in the last column for a section having a free area of 12.5 square feet ; here we find that a 5 feet by 6 feet 6 inches section has a free opening of 13 square feet and a radiating surface of 62 square 156 HEATING AND VENTILATION feet. The conditions call for 10 rows of pipes and 10 X 62 = 620 square feet of radiating surface, which is slightly more than called for, but which would be near enough for all practical purposes. EXAMPLE FOR PRACTICE Compute the dimensions of a heater to warm 20,000 cubic feet of air per minute from 10 below zero to 70 degrees above, with 5 pounds steam pressure. ANS. 1,164 sq. ft. of rad. surface 10 pipes deep. 25 sq. ft. free area through heater. Use twenty 5 ft. by 6 ft. sections, side by side, which gives 24 square feet area and 1,140 square feet of surface. The general method of computing the size of heater for any given building is the same as in the case of indirect heating. First obtain the B. T. U. required for ventilation, and to that add the heat loss through walls, etc.; and divide the result by the efficiency of the heater under the given conditions. Example. An audience hall is to be provided with 400,000 cubic feet of air per hour. The heat loss through walls, etc., is 250,000 B.T.U. per hour in zero weather. What will be the size of heater, and how many rows of pipe deep must it be, with 20 pounds steam pressure? 400,000X70 = 509j()90 B T n for venti i ation . oo Therefore 250,000 + 509,090 = 759,090 B. T. U., total to be supplied. We must next find to what temperature the entering air must be raised in order to bring in the required amount of heat, so that the number of rows of pipe in the heater may be obtained and its corre- sponding efficiency determined. We have entering the room for pur- poses of ventilation, 400,000 cubic feet of air every hour, at a tempera- ture of 70 degrees; and the problem now becomes: To what tem- perature must this air be raised to carry in 250,000 B. T. U. additional for warming? We have -learned that 1 B. T. U. will raise 55 cubic feet of air 1 degree. Then 250,000 B. T. U. will raise 250,000 X 55 cubic feet of air 1 degree. 250,000 X 55 400,000 The air in this case must be raised to 70 -+ 34 = 104 degrees, to provide HEATING AND VENTILATION 157 for both ventilation and warming. Referring to Table XXX, we find that a heater 12 pipes deep will be required, and that the corre- sponding efficiency of the heater will be 1,650 B. T. IT. Then ' 1 ,ooO = 460 square feet of surface required. Efficiency of Cast=Iron Heaters. Heaters made up of indirect pin radiators of the usual depth, have an efficiency of at least 1,500 B. T. U., with steam at 10 pounds pressure, and are easily capable of warming air from zero to 80 degrees or over when computed on this basis. The free space between the sections bears such a relation to the heating surface that ample area is provided for the flow of air through the heater, without producing an excessive velocity. The heater shown in Fig. 139 may be counted on for an effi- ciency at least equal to that of a pipe heater; and in computing the depth, one row of sections may be taken as representing 4 rows of Pipe- Pipe Connections. In the heater shown in Fig. 135, all the sections take their supply from a common header, the supply pipe connecting with the top, and the return being taken from the lower division at the end, as shown. In Fig. 137 the base is divided into two parts, one for live steam, and the other for exhaust. The supply pipes connect with the upper compartments, and the drips are taken off as shown. Separate traps should be provided for the two pressures. The connections in Fig. 136 are similar to those just described, except that the supply and return headers, or bases, are drained through separate pipes and traps, there being a slight difference in pressure between the two, which is likely to interfere with the proper drainage if brought into the same one. This heater is arranged to take exhaust steam, but has a connection for feeding in live steam through a reducing valve if desired, the whole heater being under one pressure. In heating and ventilating work where a close regulation of temperature is required, it is usual to divide the heater into several sections, depending upon its size, and to provide each with a valve in the supply and return. In making the divisions, special care should be taken to arrange for as many combinations as possible. For example, a heater 10 pipes deep may be made up of three sections one of 158 HEATING AND VENTILATION 2 rows, and two of 4 rows each. By means of this division, 2, 4, 6, 8, or 10 rows of pipe can be used at one time, as the outside weather conditions may require. When possible, the return from each section should be provided with a water-seal two or three feet m depth. In the case of overhead heaters, the returns may be sealed by the water-line of the boiler or by the use of a special water-line trap; but vertical pipe heaters resting on foundations near the floor are usually provided with siphon loops extending into a pit. If this arrangement is not convenient, a separate trap should be placed on the return from each section. The main return, in addition to its connection with the boiler or LIVE STEAM TRAP TRAP Fig. 140. Heater Made Up of Interchangeable Sections. pump receiver, should have a connection with the sewer for blowing out when steam is first turned on. Sometimes each section is pro- vided with a connection of this kind. Large automatic air-valves should be connected with each section; and it is well to supplement these with a hand pet-cock, unless individual blow-off valves are provided as described above. If the fan is driven by a steam engine, provision should be made for using the exhaust in the heater; and part of the sections should be so salved that they may be supplied with either exhaust or live steam. HEATING AND VENTILATION 159 Fig. 140 shows an arrangement in which all of the sections are interchangeable. From 50 to 60 square feet of radiating surface should be provided in the exhaust portion of the heater for each engine horse-power, and should be divided^into at least three sections, so that it can be proportioned to the requirements of different outside temperatures. Pipe Sizes. The sizes of the mains and branches may be com- puted from the tables already given in Part II, taking into account the higher efficiency of the heater and the short runs of piping. Table XXXII, based on experience, has been found to give satisfactory results when the apparatus is near the boilers. If the main supply pipe is of considerable length, its diameter should be checked by the method previously given. TABLE XXXII Pipe Sizes SQUARE FEET OF SURFACE DIAMETER OF STEAM PIPE DIAMETER OF RETURN 150 2 inches H inches 300 2* 1* 500 3 2 700 3i 2 1,000 4 2J 2,000 5 2* 3,000 6 3 Heaters of the patterns shown in Figs. 135, 136, and 137 are usually tapped at the factory for high or low pressure as desired, and these sizes may be followed in making the pipe connections. The sizes marked on Fig. 136 may be used for all ordinary work where the pressure runs from 5 to 20 pounds; for pressures above that, the supply connections may be reduced one size. FANS There are two types of fans in common use, known as the cen- trifugal fan or blower, and the disc fan or propeller. The former consists of a number of straight or slightly curved blades extending radially from an axis, as shown in Fig. 141. When the fan is in motion, the air in contact with the blades is thrown outward by the action of centrifugal force, and delivered at the circumference or 160 HEATING AND VENTILATION periphery of the wheel. A partial vacuum is thus produced at the center of the wheel, and air from the outside flows in to take the place of that which has been discharged. Fig. 142 illustrates the action of a centrifugal fan, the arrows showing the path of the air. This type of fan is usually enclosed in a steel -plate casing of such form as to provide for the free move- ment of the air as it es- capes from the periphery of the wheel. An opening in the circumference of the casing serves as an outlet into the distributing ducts which carry the air to the various rooms to be venti- lated. A fan with casing, is shown in Fig. 143; and a combined heater and fan, with direct -connected engine, is shown in Fig. 144. The discharge opening can be located in any position desired, either up, down, top horizontal, bottom horizontal, or at any angle. Where the height of the fan room is limited, a form called the three-quarter housing may be used, in which the lower part of the casing is replaced by a brick or cemented pit extending below the floor- level as shown in Fig. 145. Another form of centrifugal fan is shown in Fig. 146. This is known as the cone fan, and is commonly placed in an opening in a brick wall, and discharges air from its entire periphery into a room called a plenum chamber, with which the various distributing ducts connect. This fan is often made double by placing two wheels back to Fig. 141. Centrifugal Fan or Blower. Fig. 142. Illustrating Action of Centrifugal Fan. The Arrows Show the Path of the Air. HEATING AND VENTILATION 16) back and surrounding them with a steel casing in a similar manner to the one shown in Fig. 143. Cone fans are particularly adapted to church and schoolhouse work, as they are capable of moving large volumes of air at moderate speeds. Fig. 147 shows a form of small direct-connected exhauster com- monly used for ventilating toilet-rooms, chemical hoods, etc. Centrifugal fans are used almost exclusively for supplying air for the ventilation of buildings, and for forced-blast heating. They are also used as exhausters for removing the air from buildings in cases where there is considerable resist- ance due to the small size or excessive length of the discharge ducts. General Proportions. The general form of a fan wheel is shown in Fig. 141, which represents a single spider wheel with curved blades. Those over 4 feet in diameter usually have two spiders, while fans of large size are often pro- vided with three or more. The number of floats or blades commonly varies from six to twelve, depending upon the diameter of the fan. They are made both curved and straight; the former, it is claimed, run more quietly, but, if curved too much, will not work so well against a high pressure as the latter form. The relative proportions of a fan wheel vary somewhat in the case of different makes. The following are averages taken from fans of different sizes as made by several well-known manufacturers for general ventilating and similar work: Width of fan at center = Diameter X .52 Width of fan at perimeter = Width at center X .8 Diameter of inlet = Diameter of wheel X .68 Fig. 143. Centrifugal Fan with Casing. 162 HEATING AND VENTILATION Fig. 144. Combined Heater and Centrifugal Fan with Direct-Connected Engine. Fig. 145. Centrifugal Fan in "Three-Quarter Housing." Used where Headroom is Limited ; Extra Space Provided by Pit under Floor-Level. HEATING AND VENTILATION 163 Fans are made both with double and with single inlets, the former being called blowers and the latter exhausters. The size of a fan is commonly expressed in inches, which means the approximate height of the casing of a full-housed fan. The diameter of the wheel is usually expressed^in feet, and can be found in any given case by dividing the size in inches by 20. For example, a 120-inch fan has a wheel 120 -r 20 = 6 feet in diameter. Fig. 146. "Cone" Fan. Discharges through Opening in Wall into a " Connecting with Distributing Ducts. Plenum Chamber' Theory of Centrifugal Fans. The action of a fan is aft'ected to such an extent by the various conditions under which it operates, that it is impossible to give fixed rules for determining the exact results to be expected in any particular instance. This being the case, it seems best to take up the matter briefly from a theoretical 164 HEATING AND VENTILATION standpoint, and then show what corrections are necessary in the case of a given fan under actual working conditions. There are various methods for determining the capacity of a fan at different speeds, and the power necessary to drive it; each manufacturer has his own formulae for this purpose, based upon tests of his own particular fans. The methods given here apply in a general way to fans having proportions which represent the average of several standard makes; and the results obtained will be Fig. 147. Small, Direct-Connected Exhauster for Ventilating Toilet-Rooms, Chemical Hoods, etc. found to correspond well with those obtained in practice under ordinary conditions. As already stated, the rotation of a fan of this type sets in motion the air between the blades, which, by the action of centrifugal force, is delivered at the periphery of the wheel into the casing surrounding it. As the velocity of flow through the discharge outlet depends upon the pressure or head within the casing, and this in turn upon the velocity of the blades, it becomes necessary to examine briefly into the relations existing between these quantities. HEATING AND VENTILATION 165 Pressure. The pressure referred to in connection with a fan, is that in the discharge outlet, and represents the force which drives the air through the ducts and flues. The greater the pressure with a given resistance in the pipes, the greater will be the volume of air delivered; and the greater the resistance, the greater the pressure required to deliver a given quantity. The pressure within a fan casing is caused by the air being thrown from the tips of the blades, and varies with the velocity of rotation; that is, the higher the speed of the fan, the greater will be the pressure produced. Where the dimensions of a fan and casing are properly proportioned, the velocity of air-flow through the outlet will be the same as that of the tips of the blades, and the pressure within the casing will be that corresponding to this velocity. Table XXXIII gives the necessary speed for fans of different diameters to produce different pressures, and also the velocity of air- flow due to these pressures. TABLE XXXIII Fan Speeds, Pressures, and Velocities of Air-Flow s lee DIAMETER OF FAN WHEEL, IN FEET - - - a H . &H ^ a r <* t> w 03 . 3 4 5 6 7 8 9 10 fc S5 I** z, Valves 58 Vent flues Ventilation air required .for horse-power for principles of 7 W Warm-air flues Warming, systems of INDEX 221 Warming, systems of Page direct hot water 4 direct-indirect radiators 4 direct steam electric heating. . . ., : 6 exhaust steam !*. 5 forced blast 6 furnaces 1 indirect hot water 5 indirect steam 3 stoves 1 Water-seal motor 142 Water-tube boilers 39 Webster vacuum heating system 141 PEC 1 f I 79734 -.-.*