VENTILATION HEATING THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES VENTILATION AND HEATING PRINCIPLES AND APPLICATION A TREATISE B. F. STURTEVANT CO. BOSTON, MASS. NEW YORK. PHILADELPHIA. CHICAGO. STURTEVANT ENGINEERING Co. LONDON. GLASGOW. STOCKHOLM. BERLIN. PARIS. CATALOGUE No. 84. COPYRIGHT, 1896, BY B. F. STURTEVANT CO. SIXTH EDITION, 1906. 1 H 7652 INTRODUCTORY L THOUGH it is nearly twenty years since the first edition of this Treatise was issued, this comparatively brief period has witnessed an almost phenomenal change in public opinion regarding the absolute necessity of good ventilation. That the evil effedls of foul air are now generally appreciated is best evidenced by the legal enactments which control the application of ventilating systems in many of our States and municipalities. The growing realisation of the necessity of mechanical means to secure positive and reliable results is likewise evident in the extensive and increasing in- troduction of the Sturtevant System. Appreciating the value of former editions of this, Treatise as a means of advancing the cause of improved ventilation and of increasing the application of the Sturtevant System, it is here presented entirely revised and greatly enlarged, with the sincere desire to place before the reader, as clearly and concisely as possible, the points to be considered and the steps to be taken in deciding upon a system of heating and ventilation. The suc- ~\ cessful operation of the Sturtevant System in thousands of buildings in this country and in Europe is the best evidence we have to offer as to its efficiency. B. F. STURTEl/ANT CO. 379442 VENTILATION HEATING VENTILATION. NECESSITY OF VENTILATION. Until quite recently ventilation has been generally regarded as a luxury rather than as an absolute necessity. The discomfort of a poorly-ventilated room has been realized with sufficient vividness, but the difficulty of substituting for the debilitating atmosphere one that is pure and invigorating has in many cases been so far beyond the power of ordinary methods to accomplish that a crowded apartment and a vitiated atmosphere have been looked upon as inseparable. But such an atmosphere is more than uncomfortable and disagreeble; it is positively and undeniably injurious, and continued exposure to it is certain to lead to serious consequences. The evil effects of lack of ventilation are made only too evident by such facts as that "death-rates have been reduced by the introduction of efficient ventilating systems, in children's hospitals, from 50 to 5 per cent.; in surgical wards of general hospitals, from 44 to 13 per cent.; in army hospitals, from 23 to 6 per cent. * * * Prison records show reduced death-rates, chiefly as the result of effective ventilation, in one case from the yearly average of eighty deaths to one of eight, each period covering the same and a considerable number of years. * * * The annual death-rate among horses in army stables in the German service has been reduced by more roomy quarters and free ventilation from 19 to 1.5, and in a time of epidemic in Boston the number of horses lost in badly-ventilated stables was five to one in those well ventilated."* While such figures show directly traceable results of breathing impure air, it is not in these most serious consequences alone that its evil effects are revealed. A vitiated atmosphere lowers the vitality, increases the susceptibility to and severity of disease, and decreases the physical and mental working power of the * Notes on Ventilation and Heating : Prof. S. H. Woodbridge, Mass. Inst. Tech., Boston. VENTILATION AND HEATING individual, and, while not producing sudden death, nevertheless inevitably shortens life. AIR. Air being the prime supporter of life, health, and even life itself, are dependent upon the composition of the atmosphere. Although simply a me- chanical mixture, yet certain gases of which it is composed exist in almost un- alterable proportions in the normal atmosphere. Oxygen and nitrogen, the principal constituents, are present in very nearly the proportion of one part of oxygen to four parts of nitrogen. Carbonic acid gas, the result of all combustion, either slow or rapid, exists in the very small proportion of three to four parts in ten thousand of air, while the aqueous vapor varies greatly with the temperature and exposure to water. In addition there is generally present in air in variable but exceedingly small quantities, ammonia, sulphureted hydrogen, sulphurous acid gas, floating organic and inorganic matter and local impurities. GRAINS OF MOISTURE PER CUBIC FOOT OF AIR. FIG. 1. HYGROMETRIC CHART. HUMIDITY. The condition of the atmosphere with relation to the amount of vapor or water which it holds in suspension is expressed by the term humidity. Actual Humidity relates to the actual weight of water vapor present in a giver unit volume of air, while the term Relative Humidity expresses the relation be- tween the vapor actually present in the air and that which it would contain if saturated. Obviously the air is saturated with moisture when it will hold no more. The actual humidity varies excessively with the temperature; it is, there- fore, evident that a statement of the relative humidity gives no indication of the VENTILATION AND HEATING TABLE No. 1. OF THE WEIGHTS OF AIR, VAPOR OF WATER, AND SATURATED MIXTURES OF AIR AND VAPOR AT DIFFERENT TEMPERA- TURES, UNDER THE ORDINARY ATMOSPHERIC PRES- SURE OF 29.921 INCHES OF MERCURY. 1 Temperature. Fahrenheit. Volume of Dry Air at different temper- M atures, the volume at }3 being i.ooo. Weight of a Cubic ., Foot of Dry Air at w different tempera- tures, in pounds. Ill *-g O r^ U fc-=tf % o 3 3 & u >% 4 MIXTURES OF AIR SATURATED WITH VAPOR. Cubic Ft of Vapor II ,_, from i Ib. of Water * at its own pressure in column 4. || glisf Sfslf giSjg a|i^ s-sgsj 5 WEIGHT OF CUBIC FOOT OF THE MIXTURE OF AIR AND VAPOR. >R- Vg-S-S mi liP 9 ail, <1 &i <~ 1O Mrf J4l S* 6 *0 0-8 W O.C %>l Hi 7 Total Weight of 00 Mixture in pounds o 935 .0864 .044 29.877 .0863 .000079 .086379 .00092 1092.4 12 .960 .0842 .074 29.849 .0840 .000130 .084130 00155 646.1 22 .980 .0824 .118 29.803 .0821 .000202 .082302 .00245 406.4 32 I.OOO .0807 .181 29.740 .0802 .000304 .080504 00379 263.81 3289 42 1.020 .0791 .267 29.654 .0784 .000440 .078840 .00561 178.18 2252 52 I.04I .0776 -388 29-533 .0766 .000627 .077227 .00819 122.17 1595 62 1.061 .0761 55 6 29-365 .0747 .000881 7558l .01179 84.79 "35 72 1.082 .0747 .785 29.136 .0727 .001221 073921 .01680 59-54 819 82 1. 102 0733 1.092 28.829 .0706 .001667 .072267 .02361 42-35 600 92 1. 122 .0720 1.501 28.420 .0684 .002250 .070717 .03289 30-40 444 102 I-I43 .0707 2.036 27.885 .0659 .002997 .068897 04547 21.98 334 112 I.l6 3 .0694 2-731 27.190 .0631 .003946 .067046 .06253 J 5-99 253 122 I.l8 4 .0682 3.621 26.300 0599 .005142 .065042 .08584 11.65 194 132 1.204 .0671 4-752 25.169 .0564 .006639 .063039 .11771 8-49 J 5* 142 1.224 .0660 6.165 23-756 .0524 .008473 .060873 .16170 6.18 118 152 1-245 .0649 7-930 21.991 .0477 .010716 .058416 .22465 4-45 93-3 162 1.265 .0638 10.099 19.822 .0423 OI34I5 055715 3I7I3 3-i5 74-5 172 I.2S5 .0628 12.758 17.163 .0360 .016682 .052682 .46338 2.16 59-2 182 1.306 .0618 15.960 13.961 .0288 .020536 049336 .71300 1.402 48.6 192 1.326 .0609 19.828 10.093 .0205 .025142 -045642 1.22643 -815 39-8 202 J-347 .0600 24.450 5-471 .0109 030545 .041445 2.80230 357 32.7 212 1-367 .0591 29.921 o.ooo .0000 .036820 .036820 Infinite. .000 27.1 VENTILATION AND HEATING exact amount of vapor present unless the moisture carrying capacity of the air at the given temperature be known. The accompanying Table No. 1 gives a clear idea of the relations existing between the weights of air and vapor, in saturated mixtures at different tem- peratures, and will be found exceedingly useful in all calculations relating to heating and drying. A portion of this table is more clearly represented graphically by the hygro- metric chart, Fig. 1, the rapid increase in the capacity of the air for carrying off moisture, as the temperature of the air rises, being indicated by the curved lines, which represent 10, 20, etc., to 100 per cent, humidity: 100 per cent, being the dew point. The horizontal line of figures, from 10 to 200, at the top of the chart, indicates the grains of moisture per cubic foot of air, while the temperature of the air is given in degrees Fahrenheit at the left of the chart. CARBONIC ACID GAS. This gas is of itself only a neutral constituent of the atmosphere, like nitrogen, and, contrary to general impressions, its un- associated presence in moderately large quantities as in soda-water manufacto- ries is neither disagreeable nor particularly harmful. But its presence in the air provided for respiration decreases the readiness with which the carbon of the blood unites with the oxygen of the air to form, in the lungs, further amounts of carbonic acid. It is evident, therefore, that when present in sufficient quantity, it may indirectly bring about not only serious but fatal results. The true evil of a vitiated atmosphere lies in its other constituent gases and in the micro-organisms which are produced in the process of respiration. It is known, however, 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 may be easily deter- mined by experiment, the fixing of a standard limit of the amount in which it may be allowed in ventilated rooms also limits the permissible vitiation of the atmosphere by other impurities. When carbonic acid is present in excess of 10 parts to 10,000 parts of air, a feeling of weariness and stuffiness, generally accompanied by a headache, will be experienced, while even with 8 parts in 10,000 parts a room would be con- sidered close. For general considerations of ventilation the limit should be olaced at 6 to 7 parts in 10,000, thus allowing an increase of 2 to 3 parts per 10,000 over that present in outdoor air, which may be considered to contain 4 parts in 10,000 under the ordinary conditions of a populous district. The exceedingly bad condition of the air in many halls and theatres is VENTILATION AND HEATING demonstrated by the following results of experiments by Professor Woodbridge in various buildings in Boston.* PLACE AND TIME. PARTS OF CARBONIC ACID GAS IN 10,000 PARTS OF AIR. Floor. First Balcony. Second Balcony. Gallery. f 1st Test, . . 48.7 BOSTON THEATRE. \ 2d Test . . 39.13 42.86 44.72 48.14 ( 3d Test, . . 35.48 . 45.12 PIORFTHFATRF f Three-fourths full, 23.38 35-88 34.59 r " EATRE - \0ne-halffull . 19. 24.16 24.72 HUNTINGTON HALL. Ventilating apparatus unused 18.48 to 17.24 YOUNG MEN'S CHRISTIAN ASSOCIATION . 36.43 to 32.59 TRINITY CHURCH. Gallery 20.52 to 19.12 In these cases injurious effects could not fail to ensue from a continued exposure to such seriously contaminated air. AMOUNT OF AIR REQUIRED FOR VENTILATION. Under the general conditions of outdoor air, namely 70 temperature and 70 per cent, of complete saturation, an average adult man, when sitting at rest as in an audience, makes 16 respirations per minute of 30 cubic inches each, or 480 cubic inches per minute. Under the previously assumed conditions of 70 temperature and 70 per cent, humidity, the air thus inhaled will consist of about \ oxygen and I nitrogen, together with about liV per cent, aqueous vapor and res of a per cent, carbonic acid. By the process of respiration the air will, when exhaled, be found to have lost about i of its oxygen by the formation of carbonic acid, which will have increased about one hundred -fold, thus forming about 4 per cent., while the water vapor will form about 5 per cent, of the volume. In ad- dition, the inhaled air will have been warmed from 70 to 90, and, notwith- standing the increased proportion of carbonic acid, which is about one and one-half times heavier than air, will, owing to the increase of temperature and the levity of the water vapor, be about 3 per cent, lighter than when inhaled. Thus it will be seen that this vitiated air will not fall to the ground, as has often been presumed, but will naturally rise above the level of the breathing line, and the carbonic acid will immediately diffuse itself into the surrounding air. In ad- dition to the carbonic acid exhaled in the process of respiration, a small amount is given off by the skin. Furthermore, 1 i to 2\ Ibs. of water are evaporated daily from the surface of the skin of a person in still life. If the air supply at 70 is assumed to have a humidity of 70 per cent, and to be saturated when it leaves the body at a higher temperature, then at least 4 cubic feet of air per minute will be required to carry away this vapor. * Technology Quarterly, Vol. II. No. 2. VENTILATION AND HEATING Taking into consideration these various factors, it becomes evident that at least 4z cubic feet of fresh air will be required per minute for respiration and for the absorption of moisture and dilution of carbonic acid gas from the skin. This, however, is only on the assumption that any given quantity of air having fulfilled its office, is immediately removed without contamination of the surrounding atmosphere ; but this condition is impossible, for the spent air from the lungs, containing about 400 parts of carbonic acid gas in 10,000, is immedi- ately diffused in the atmosphere. The carbonic acid does not fall to the floor as a separate gas, but is intimately mixed with the air and equally distributed throughout the apartment. It must then be evident that ventilation is in effect but a process of dilution and that when the vitiation of the air discharged from the lungs is known and the degree of vitiation to be maintained in the apartments is decided, the necessary con- stant supply of fresh air to maintain this standard may be very easily determined. For the purpose of calculation, 0.6 cubic feet per hour is accepted as the average production of carbonic acid by an adult at rest and the proportion of this gas in the external air as 4 parts in 10,000. If, therefore, the degree of vitiation of the occupied room be maintained at, say, 6 parts in 10,000, there will be per- missible an increment of only 2 parts in 10,000 above that of the normal atmosphere, or 2- 10,000=. 0002 of a cubic foot of carbonic acid in each cubic foot of air. The 0.6 cubic foot of carbonic acid produced per hour by a single individual will, therefore, require for its dilution to this degree 0.6-^.0002=3,000 cubic feet of air per hour. Upon this basis the following Table has been calculated : Cubic Feet of Air Con- taining 4 Parts of Carbonic Acid in 10,- *i 1 1 I 1 1 I 1 I 1 S 5 000 Supplied per Per- son fc.S oO (. \f\ 6 62 1 R Degree of Vitiation of the Air in the Room. Parts of Car- bonic Acid in 10,000. 5 5.5 6 6.5 7 7.33 7-5 8 9 10 15 20 30 The figures indicate absolute relations under the stated conditions, and are generally applicable to the ventilation of schools, churches, halls of audience and the like, where the occupants are reasonably healthy and remain at rest. But the absolute air volume to be supplied cannot be specified with certainty in ad- vance, without a thorough knowledge of all the conditions and modifying circum- 10 VENTILATION AND HEATING stances, in fact, the climate, the construction of the building, the size of the rooms, the number of occupants, their healthfulness and their activity, together with the time during which the rooms are occupied, all have their direct influences. Under all these considerations, it is readily seen that no standard allowance can be made to suit all circumstances, and results will be satisfactory only in so far as the designer understandingly, with the knowledge of the various requirements as they have here been given, makes such allowance. The following schedule of air supply, in cubic feet per hour, as proposed by Dr. Billings* is here presented as showing relatively the volumes recommended by him in different classes of buildings : CUBIC FEET PER HOUR. Hospitals 3,600 per Bed Legislative Assembly Halls, 3,600 per Seat Barracks, Bedrooms and Workshops, . 3,000 per Person Schools and Churches, " . . . 2,4OO per Person Theatres and Ordinary Halls of Audience, . . . . ... 2,000 per Seat Office Rooms, . 1,800 per Person Dining Rooms, 1,800 per Person These figures are for buildings in which there is no special contamination of the atmosphere beyond that which their use would indicate. Where smoke, dust, noxious gases or infectious germs are produced, and above all where the illumination is furnished by candles, lamps or gas, additional provision of air supply must be made. Thus a single 4 1-2 gas burner demands 45 cubic feet of air per minute and the resulting carbonic acid gas, unless sufficiently diluted, or immediately removed, will seriously vitiate the air. The introduction of modern methods of incandescent electric lighting has done much to simplify and facilitate the solution of problems in heating and ventilation. The air volumes recommended for ventilation by various investigators of the past century show a constant increase in their quantity as the years progress. As good ventilation is only a relative term, depending largely on one's experience and the possibility of improvement, it must be evident that perfect ventilation in the broadest sense can only be secured in the open air. It is, therefore, the province of ventilation to approach as near this perfection as means and expediency will permit. The crystallization of public opinion into statute laws, looking to adequate methods of ventilation for school, theatre, church and factory, has resulted in the establishment of a basis or limit which will meet the approval of those upon whom is placed the responsibility of enforcing these laws. Under the law as first * Ventilation and Heating: John S. Billings, New York, 1893. 11 VENTILATION AND HEATING passed in Massachusetts, the attempt was made to secure 50 cubic feet per head per minute, but it was soon discovered that such provision would necessitate the remodelling of practically every building in the State. Therefore, financial out- weighed all other influences, and the limit was dropped to 30 cubic feet, a figure adopted not because of hygienic deductions but because it appeared upon investi- gation to be the practical limit attained by existing methods in the common- wealth. This basis of 30 cubic feet has been very generally adopted throughout the country, and is to-day recognized as the minimum volume to be provided in any system of ventilation worthy of the name. As the benefits of good ventilation are still further recognized, and the ability of the fan to provide practically unlimited volumes of air is better appreciated, this limit will gradually rise until we may one day witness the compulsory provision of air for the purpose of ventilation in such volumes as to render further improvement of no practical benefit. 12 VENTILATION AND HEATING HEATING. HEAT OF HUMAN BODY. The normal internal temperature of the human body is very near 100, independent of the temperature of the surrounding air. By respiration the continuous process of slow combustion is kept up, the oxygen of the air, uniting with the carbon of the blood passing through the lungs, to form carbonic acid. As in any case of combustion, over- heating takes place unless provision is made for the distribution of the heat generated, so the body is kept at its normal temperature only by the abstraction of heat from it. The actual heating of the body is not the ultimate object of heating ; but, in reality, provision is made for the abstraction of heat generated by the vital functions without making too great a demand upon the physical endurance of the individual. MEANS OF DISPERSION OF HEAT. Three means are provided for the healthful dispersion of heat from the human body. First. By radiation to the air and surrounding objects. Second. By conduction, principally to the air immediately in contact with the body. Third. By evaporation of moisture from the lungs, throat and skin. Under the conditions of summer air, the last two are generally about equal, but the greater part of the. heat is dissipated by the first means. Air is a nearly perfect non-conductor of heat, but radiation takes place through it readily. We may enter a room having a temperature of 75, with walls at 50, and feel chilled, simply because heat is rapidly radiated from the body through the air to the colder walls. In comparatively dry air equality of temperature is kept up by a steady but imperceptible evaporation from the skin. In moist air this rapid evaporation is prevented and the water is deposited as perspiration, the air being too heavily laden to take it up. On the other hand, when the air is in motion it increases both evaporation and conduction by the constant bringing of fresh air to take the place of that already moistened or heated. If, under any circumstances, one of these three means fails to abstract heat rapidly enough, the removal by the other means is increased, and equilibrium of temperature kept up. VENTILATION AND HEATING High humidity has the effect of modifying very materially the temperature at which comfort may be secured. The excessive humidity of the atmosphere of the west and south of England has, owing to the reduced evaporation from the body, the effect of making a temperature of 56 in that country equally as comfortable as 80 in the dryer climate of Canada or Minnesota. In this country, where some means of heating is usually required during about seven months of the year, the amount of heat necessary and the economy exercised in supplying it are vital questions. As will appear in what follows, convenience and economy can best be secured by an intelligent union of the heating and ventilating systems. VENTILATION AND HEATING SYSTEMS OF VENTILATION AND HEATING. NATURAL METHODS. The requirements of good ventilation and heating being understood, the choice of the best method for carrying out such requirements presents itself. While the principles have been generally under- stood, their application has proved to be the stumbling-block over which many an architect and engineer has tripped. Natural agencies, as apparently the least expensive, have usually been first called upon to produce such currents and move such volumes of air as might be required. But it will be universally admitted that all systems of so-called "natural ventilation" have proved themselves inadequate to fulfill all requirements. A dependence upon windows and doors for ventilation cannot, with propriety, be called a system of ventilation, for the supply is ordinarily spasmodic, and, without question, disagreeable, except in so far as a cold draught of fresh air from an open window may be preferable to the vitiated and odorous air of a confined apartment. Excellent results may con- tinue for a number of days during the employment of a method of ventilation dependent upon natural agencies, but a change in the temperature or humidity, or in the direction and force of the wind, may exactly reverse the action of the system. Flues which, were designed to furnish fresh air will be found to be actionless, while foul-air ducts may be bringing the foul air from other rooms. For a crowded or continuously-occupied apartment, such arrangements are utterly \nadequate and are certain to prove entirely unequal to the task of supplying air in such quantity as has been shown to be required, above all, they are not positive. VENTILATION BY ASPIRATION. Somewhat more positive results may be obtained by warming the air within the vent flues. Gas-jets, steam-heated surfaces and the smoke flues from steam or hot-air furnaces, are employed for this purpose. But as the results attained are due to a lessened density of the air within the flue, and as the heat applied for thus warming and rarifying this air serves no other useful purpose but is dissipated in the atmosphere, the method proves to be excessively expensive when the power, as measured in heat units, required to develop this movement is taken into account. 15 VENTILATION AND HEATING FORCED CIRCULATION. In the system of forced circulation by means of that universally-adopted machine, a fan or blower, the action is absolute and positive. The whole matter cannot be better expressed than in the words of the late Robert Briggs,* a man of large experience in practical ventilation and heating : " It will not be attempted at this time to argue fully the advantages of the method of supplying air for ventilation by impulse through mechanical means, the superiority of forced ventilation, as it is called. This mooted question will be found to have been discussed, argued and combated on all sides, in numerous publications, but the conclusion of all is, that if air is wanted in any particular place, at any particular time, it must be put there, not allowed to go. Other methods will give results at certain times or seasons, or under certain conditions. One method will work perfectly with certain differences of internal and external temperatures, while another method succeeds only when other differences exist. One method reaches to relative success whenever a wind can render a cowl efficient. Another method remains perfect as a system if no malicious person opens a door or window. No other method than that of impelling air by direct means, with a fan, is equally independent of accidental natural conditions, equally efficient for a desired result, or equally controllable to suit the demands of those who are ventilated." EFFICIENCY OF THE FAN. Further on in the same paper, Mr. Briggs states that: " In all mechanical appliances, that is simplest which most positively and directly effects the purpose in view ; and in this matter of supplying air, it may be claimed that the process of impelling it, when and where wanted, is at once the most certain and efficient, and that the fan (in its form of a rotating wheel with vanes for large uses), is the simplest and readiest machine for impelling air. It will not be attempted at this time to discuss the theory of Rotary Fans. The fan itself will simply be accepted as one of the recognized appliances in the construction of ventilating apparatuses, available with other mechanisms in established forms and defined types for American practice." After showing the enormous expense of moving air by allowing it to pass over steam-heated surfaces (thus creating a difference in pressure due to a differ- ence in temperature) compared with the expense of moving equal quantities of air by means of a fan, Prof. S. H. Woodbridge,t of the Massachusetts Institute of Technology, states that " among the many mechanical devices for the move- ment of air through channels, none are so economical of power and convenient in use as the fan." * On the Ventilation of Halls of Audience : Robert Briggs ; Proc. Am. Soc. Civil Engineers, May, 1881. ( Notes on Ventilation and Heating: Prof. S. H. Woodbridge, Mass. Inst.Tech., Boston. 16 VENTILATION AND HEATING A practical illustration will best serve to prove the force of this statement. A vent flue, one square foot in cross sectional area and 40 feet high, is arranged to withdraw air from a room having a temperature of 70 while the outdoor air is at 20 ; the flue being provided with an accelerating coil, which heats the air within to 90. By the ordinary methods of calculation, it may be shown that the theoretical velocity of the air thus produced in the flue will be 1,149.4 feet per minute, and that there will be expended for its movement 394.6 heat units. A fan, on the other hand, would theoretically require, to produce the same air movement, only .703 units of heat. But these figures are purely theoretical, and the efficiency of the two methods must enter to give the true relation. Assuming for the flue an average efficiency of 60 per cent., there will actually be required for this method 657.7 units of heat. On the other hand, making the fair assumptions that of the heat units in the fuel 70 per cent, is delivered in the form of steam, that this steam is utilized in an engine having an efficiency of only 10 per cent., while the fan driven thereby turns into useful work only 25 per cent, of the power delivered to it by the engine, the combined efficiency of the system will be reduced to 1.75 per cent., calling for a heat expenditure of 40.17 units. Even under this practical condition, it appears that the movement of air by aspiration still requires 16.37 times as much heat (which is simply a measure of the coal bill), as a fan producing the same results. Of course, a change in the conditions will affect this relation to a reasonable extent, but it is certainly evident that the thermal or aspiration system requires more fuel than the fan under all practical conditions as they exist in any system of heating and ventilation. METHODS OF HEATING. In the progress of civilization more efficient arrangements for heating have gradually been adopted. Fireplaces, stoves and furnaces have, in the order named, been introduced as means of warming. For small rooms, as in dwellings, they answer very well ; but the effect of opening or closing windows and doors and of changes in the atmospheric conditions is too well appreciated to need recital here. It will certainly be admitted that a building can seldom be found where the heated air is properly and satisfactorily furnished and distributed by a furnace ; some of these influences are sure to act, and at times it will be impossible to heat certain rooms without the closing of doors or shutting of registers in other rooms. More refined are the methods of heating which are dependent upon the use of steam or hot water, confined in radiators or coils. Under systems of direct radiation, these are placed in the rooms to be heated, but seldom with any 17 VENTILATION AND HEATING provision for the introduction of fresh air. By the indirect method of placing the heating surface in ducts connecting with the rooms and permitting outdoor air to pass across such surfaces, a much nearer approach is made to good ventilation. But still it is practically impossible by such means alone to produce the air-flow and maintain the temperature necessary for a large and crowded apartment. It is evident that some positive means, like the fan, must be applied to render such systems reliable at all times. VENTILATION AND HEATING COMBINED. Experience has clearly demonstrated that in this climate no system of ventilation can be successfully operated by itself and independently of the method of heating that may be adopted. It is, in fact, a vital element of success that the two systems be most intimately combined, for they are clearly interdependent, and when properly applied are so interwoven in their operation and results that disunion is certain to bring about failure. For the purpose of ventilation, the fan was first applied upon a practical scale about the middle of this century, but only to a limited extent, and it was not until the fan and the steam heater in marketable form were introduced by B. F. Sturtevant that the so-called " Blower System " became a reality. The System, of which these two elements are the most important factors, as originally installed by this house, has naturally been known as "The Sturtevant System." This System is at once practical, successful and economical ; for, air being the natural conveyor of heat, it may, when properly warmed and supplied, perform the double office of heating and ventilating. As applied, the Sturtevant System forces the air into the apartment by the pres- sure or plenum method. When a fan is arranged to exhaust or withdraw the air from an enclosed space, the term vacuum, or exhaust method, is almost universally applied. THE EXHAUST METHOD. There are many objections to the adoption of the exhaust method in this country, and, as a rule, it should be avoided. When exhausting, a partial vacuum is created within the apartment, 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 proper means for warming it. Under this system provision is often made for drawing the air across steam pipes placed opposite windows, with the expectation that the air will become thoroughly heated in passing across them. Such oftens fails to be the case, for the most direct course is taken by the air toward the existing vacuity, and only a portion of the heating surface is utilized. 18 VENTILATION AND HEATING THE PLENUM METHOD. On the other hand, when the air is forced in, its quality, temperature and point of admission are completely under control ; in a word, the method is positive; all spaces are filled with air under a slight pressure, and the leakage is outward, preventing the drawing of polluted air into the room from any source. But, above all, ample opportunity is given for properly tempering the air by means of heaters, either in direct communication with the fan itself or in separate passages leading to the various rooms. DETERMINATION OF HEATING CAPACITY REQUIRED. The amount of heat required to comfortably warm a given space is dependent upon many variables. Most important of all is the difference in temperature between the indoor and the outdoor air ; for the rate of passage of heat through walls is practically in direct proportion to the difference in temperature upon the opposite sides of the wall. The material of such walls, of course, governs the rapidity of this loss ; under general conditions, wooden buildings most rapidly dissipate the heat, and stone next, while brick buildings best retain the heat. Obviously the relative area of window surface materially affects the loss of heat, while the amount of wall and window surface, in proportion to the cubic contents of the apartment; the climate, the location (whether high or low, or upon the side of the building subject to the most chilling winds) , and the method of heating, all have an influence. With so many modifying considerations, it is evident that no unalterable rule can be given for heating all classes of buildings, but that satisfactory results can only be obtained by separate calculation for each. From the known heat -transmitting power of various forms of construction, the loss of heat may be determined with reasonable accuracy. The conductivity of such surfaces is generally expressed in the number units of heat transmitted per hour per square foot of surface for each degree difference between the temperatures of its two sides. The entire subject has been very carefully investigated by the German Government, and the results incorporated in a series of coefficients representing the best practice to be employed in determining the relative rates of transmission for various substances employed in construction. It is prescribed by law that these coefficients shall be applied in the design of its public buildings, and generally used in Germany for all buildings. These values have been transformed into American units by Alfred R. Wolff, M. E.,* and by him slightly modified to suit our climatic conditions. The most important of these coefficients representing the heat transmission in units per hour per square foot of surface per degree difference in temperature are here presented : * The Heating of Large Buildings : Alfred R. Wolff, M.E., New York. 19 VENTILATION AND HEATING THE COEFFICIENT BEING FOR EACH SQUARE FOOT OF BRICK WALL, OF THICKNESS: Thickness of Brick Wall, in Inches, 4 8 12 16 20 24 28 32 36 40 Coefficient .658 .453 .315 .258 .228 .194 .16 5 .143 .129 .114 l square foot, wooden beam construction, ) as flooring . . . . . . . .083 planked over, or ceiled, J as ceiling . . ." . . . . .104 1 square foot, fireproof construction, ~^ as flooring . . . . . . . . .122 floored over, J as ceiling 145 1 square foot, single window 1.21 5 l square foot, single skylight 1.03 1 square foot, double window .572 l square foot, double skylight . . . 621 l square foot, vault light . . ... . . . . '. . . 1.43 l square foot, door (65% wood, 35% glass) . . . 572 l square foot, door (plain) . . . . . .414 It is further prescribed that these coefficients are to be increased respectively as follows : Ten per cent, where the exposure is a northerly one, and winds are to be counted on as important factors. Ten per cent, when the building is heated during the daytime only, and the location of the building is not an exposed one. Thirty per cent, when the building is heated during the daytime only, and the location of the building is exposed. Fifty per cent, when the building is heated during the winter months inter- mittently, with long intervals (say days or weeks) of non-heating. From the above, Mr. Wolff has also prepared a diagram, in form similar to that here given (Fig. 2), which serves to present the data graphically in the most comprehensive manner for practical application. By the use of this diagram it is possible to determine the total loss of heat by transmission from a given room, and to thereby ascertain the amount of heat,. as measured in heat units, that must be continuously supplied to the room to make good this loss and maintain the temperature. But this does not cover the additional heat necessary on account of change of air for the purposes of ventilation. 20 VENTILATION AND HEATING 10* 20 30 40 50 60" 7O 8O 90" 1OO 110 12O 130 140 150 160 170 180 12" 10 20 30 4O 50 60 70 80 90 100 110 120 130 14O 150 160 170 180 DIFFERENCE BETWEEN INDOOR AND OUTDOOR TEMPERATURE FIG. 2. HEAT TRANSMITTED, IN BRITISH THERMAL UNITS, PER HOUR PER SQUARE FOOT OF SURFACE. 21 VENTILATION AND HEATING EFFECT OF VENTILATION ON HEATING. The reduction of tern- perature within a building is the result, first, of the combined losses of heat by conduction through and radiation from windows, doors, walls, floors and ceilings, as has been pointed out ; and, second, by direct leakage or escape of air at the temperature of the room. The former varies directly with the difference between the internal and the external temperatures, and is -proportional thereto. Wherever the blower system is used, the cost of heat supply, to make good this loss, is measured by the difference between the average temperature of the air within the room and that of the air as it is first discharged into the room from the heating apparatus, disregarding losses in transit from the apparatus. The loss by leakage and escape of air is measured directly by the difference between indoor and outdoor temperatures, this representing the heat added to the air, which serves no directly useful purpose in heating. It is thus evident that with a constant volume of air the expenditure for heating will be indicated by the loss by the first method, and that for ventilation by the loss of warm air escaping by the second means. When heating alone, as the ultimate object of the introduction of the Sturtevant System, is considered, it will be found that to maintain a temperature of 70 with outdoor temperature at zero, a change of air every sixteen minutes with an entering temperature of about 140 will represent a fair average in the northern portions of this country. Under these circumstances, disregarding the weight or density of the air at different temperatures, the difference between 70 and 140 will represent the loss by radiation and conduction. If with the same entering temperature the loss is greater, the temperature of the room will be lower, and vice versa. There is thus lost T 7 A, or one-half, of all the heat by this means ; or if, for ready comparison, we represent each degree as a unit, not of heat but merely of relative measurement, there will have been lost 70 units. If, in a given time, a given volume of air is delivered to the room, its cost in total heat expenditure must be measured by the number of degrees its temperature has been raised above zero ; that is, upon our basis of comparison, it will be equivalent to 140 units. In the given time all of this air must escape at the temperature of the room, which is here 70 ; hence the loss by this means will also be 70 units, and it can by no means be reduced except by deliberately decreasing the volume of air admitted, or by increasing the difference between internal and external tempera- tures. It is evident that with a fan running at constant speed and delivering a stated volume of air, the ventilation may be reduced by returning a portion of the air from the building, and the expenditure likewise lessened. The loss by 22 VENTILATION W HEATING radiation and conduction, on the other hand, can be reduced by sufficient, although perhaps extravagant, expenditure for double or triple sash, thicker walls, back plaster, sheathing paper, and the like. If, with the same air change, all the air should be returned from the building on the impossible assumption that there is no leakage, the temperature of the air admitted would still require to be 140, and the loss by radiation and conduc- tion would be the same, namely 70 units, but the leakage would be reduced to zero, and the total heat expenditure would be only one-half of that in the former instance. If, now, under the same conditions of construction the building be fully occu- pied and the demands of ventilation be considered, it will be necessary to reduce the time of air change, i.e., increase the volume of air delivered. If the building be occupied as a school, with the ordinary ratio of about 250 cubic feet of room- space per pupil, it will be necessary, in order to supply 30 cubic feet of air per minute per pupil, to furnish a volume equivalent to changing the air once in about eight minutes. With outdoor air still at zero and an indoor temperature to be maintained at 70, it is evident that with the air supply just double that in the first instance (as would be true with the eight-minute change), its temperature need not be as high ; in fact, as the real heating power of the admitted air is measured only by its temperature above 70, which was 140 70= 70 in the former instance, there will now be required, with double the air volume, only one-half the temperature increment, or 35. Compared by units, it will, therefore, be necessary to provide for the loss by leakage twice as many as before, that is, 2 X 70 = 140. To these must be added those supplied for radiation and conduction, which, with twice the volume of air and an increment of 35, will still equal 70 units, or a total of 140 -f- 70 = 210 units. But as the volume is double, its temperature, volume for volume, as compared with the first illustration, will be 210-^-2 = 105, which evidently equals 70 + 3 5 degrees. To summarize, there will now be required 210 units as against 140 units in the first instance, an increase of 50 per cent., and three times as many as under the assumed condition of all return air to the apparatus, while the temperature of the admitted air stands at 140 for the sixteen-minute and 105 for the eight- minute change. These propositions are more clearly presented in the accompanying diagram, Fig. 3, of the cost of heating and ventilation, with the relative cost of heating alone, and of temperatures of entering air. Of course, it is impossible to make 23 VENTILATION AND HEATING 340 320 300 280 \ \ \ \ \ V \ I \ 180 160 140 120 100 80 \ \ \ \ \ ^ \ r x A S ,. ^^ ^ o ^- ^^ ^ ^ ^-- -^" ^^ ^^^ i ^~~ I f \\ ^ ^^ flW> -^* \e& ^ -^** , --** ""^"^ ^- . ' 265 50,262 51,233 52,243 53,222 54,239 55,2i8 56,233 35 45,349 46,535 47-55 i 48.553 49,535 50,492 51,488 52,452 53,454 54,419 55,420 45 44,823 45,994 46,999 47,989 48,834 49>907 50,890 51,844 52,834 53,788 54,777 55 44.39 1 45,55i 46,546 47,527 48,488 49,413 50,399 51,344 52,325 53,270 54,248 65 44,002 45> HO 46,139 47,110 48,064 48,993 49,956 50,907 5L866 52,831 53,774 75 43,665 44,806 45,785 46,746 47,695 48,616 49,575 50,504 51,469 52,399 53,362 85 43,36i 44,493 45,466 46,424 47,36i 48,279 49,230 50,153 5i,iii 52,034 52,990 95 43,084 44,209 45^76 46,127 47,060 47,969 48,905 49,832 50,784 51,701 52,652 105 42,829 43,972 44,908 45,854 46,780 47,68 4 48,626 49,538 50,485 51,395 52-339 Per ct. of above amounts that will he heated i if air is satu- rated. 99.8 99.6 99-4 99.0 98.6 98.0 97.1 96.0 94-5 90.1 From a knowledge of the number of units of heat required, or the total weight of steam necessary per unit of time for any given building, it is a simple matter to deduce the size and capacity of the boiler to be provided. A proper understanding of the relative values of high and low pressure steam will result in due consideration being given to this factor in deciding upon the boiler capacity. EFFICIENCY OF HEATING SURFACE. The character and efficiency of the heating surface does not enter into such calculations as have just been described. The number of heat units necessary to be transmitted to the air in a given time being known, it rests with the designer to determine the amount and arrangement of heating surface to be provided to secure the desired results. Obviously, the higher the efficiency of such surface, i.e., the greater the number 30 VENTILATION AND HEATING of pounds of steam that may be condensed per hour per square foot of heating surface, the smaller and, other things being equal, the less expensive that surface will be. The efficiency of any heating surface must be directly dependent, first, upon its character and arrangement, and, second, upon the volume of air passing across it. Under the conditions of an open-pipe radiator with air surrounding it at an average temperature of 60, Robert Briggs gives, as the factor accepted by him, a loss of 1.8 units per hour per square foot of heating surface per degree difference of temperature between the steam inside and the air outside. Other writers and investigators give somewhat varying values. Taking the air tem- perature at 60 and the temperature of exhaust steam at 216 (nearly), the difference would be 156, and the number of units given out per hour per square foot of heating surface would be 156X1.8 = 280.8 units. The latent heat of steam at atmospheric pressure is 965.7 (column 3, Table No. 2), therefore, MH = .29 pounds of steam would be condensed per hour per square foot of heating surface. A similar calculation gives .44 pounds with steam at 70 pounds gauge pressure. Direct experiments made at the works of this Company, on a series of pipes exposed to air of about 60 and strung around a room at about three inches from a cold brick wall, showed a condensation somewhat greater than this, but probably due to several modifying influences, particularly that of the cold wall. Under such an arrangement a large proportion of the heat is given up by radiation to the air and surrounding objects, the remainder being conducted directly to the air which passes across the surface. These two means exist as the opportunities for the communication of heat convection, so-called, being only a form of conduction. Radiation takes place in straight lines, so that a given amount of surface becomes less efficient as a radiator, as it is massed in such form as to interfere with the radiation of heat directly to the surrounding objects. Air is a very poor absorber of radiant heat, so that it is evident that the effi- ciency of a massed coil can only be increased by giving it greater opportunity for conduction of heat from its surface to the air with which it is in contact. In other words, by increasing the air flow across this surface in such a way that the heat may be almost literally wiped off and carried to a point where the air may advantageously part with it. Upon this principle the hot-blast apparatus is designed and its high efficiency secured. Many factors enter to determine the form, proportions and general arrangement of the heating surface, as well as the permissible air volume, in such an apparatus. Appreciating the necessity of the most reliable data, and knowing that nothing of the kind existed, this Company conducted an exhaustive series 31 VENTILATION AND HEATING of experiments, covering several winter months, upon various forms of specially- constructed apparatus, to obtain all necessary data for the correct design and construction of its apparatus, as well as the intelligent application of the same. By means of formulas derived from these experiments, we are enabled to make most accurate determinations of resulting temperatures and steam condensation under given conditions, as well as to design new work with the most positive assurance of success. Among other results it was shown that in the Sturtevant Heaters a con- densation was ordinarily obtained of 2 to 21 pounds of high-pressure steam per hour per square foot of heating surface. Of course, the amount of condensa- tion is dependent upon numerous variables, the steam pressure, the specific arrangement of the heating surface, the initial temperature and the velocity of the air. Compared with the previous figures upon direct radiation, the enormous gain in efficiency is evident. A conservative estimate would, therefore, indicate the Sturtevant Heater Jo be at least three to five times more efficient than an open-pipe radiator. HEATING SURFACE REQUIRED. The total amount of heat necessary, as measured in heat units, having been determined by calculation and the effi- ciency of the selected form of heating surface being known, it is a comparatively simple matter to decide upon the amount of heating surface required for any given building. But all the conditions must be taken into consideration ; the calculations must be made for the minimum winter temperature, the steam pressure must be known, and it must be decided whether the air is to be taken entirely from out-of-doors to the heating apparatus, or to some extent returned from the building. As already shown, this latter practice is conducive to economy, but, of course, is not to be employed except where heating is the primary object in the introduction of the system, or the normal supply of air is very large per capita. While quantity of heating surface is of the utmost importance, its arrange- ment is hardly less important. It is not enough to have a given number of lineal feet of steam coils, or pipes spaced a given distance on centres, but it is further necessary to have the sections or groups of pipes combined in such form that there may be sufficient free area between the pipes to allow of the ready passage of the air handled by the fan, while the total number of pipes with which a given particle of air comes in contact in its passage through the heater must be such as to secure the requisite rise in temperature of that air. Those who do not possess extended experience in such matters are very apt to so . 32 VENTILATION AND HEATING arrange their heating surface as to greatly reduce its efficiency, with resulting failure in the heating of the building in which it is installed. One of the important objects in view in conducting the tests on Sturtevant Heaters, previously alluded to, was to determine definitely the influence of dif- ferent arrangements of heating surface of the same general character and to ascertain the form in which it could be rendered most efficient. In other words, to place this Company in a position to specify with certainty of the results to be accomplished, the most economical arrangement of the heating surface, thereby decreasing the first cost of the apparatus without impairing or affecting its efficiency. It is obviously impossible to give in practical form all of the data thus obtained, but a statement of the general practice, as it now obtains, may at least guide somewhat in the rough planning of heating and ventilating systems, and serve reasonably well as a check upon calculations made by the methods already described. In hot-blast heating, the proportional heating surface is generally expressed in the number of net cubic feet in the building for each lineal foot of one inch steam pipe in the heater. On this basis, in factory practice, with all of the air taken from out-of-doors, there is generally allowed from 100 to 1 50 cubic feet of space per foot of pipe, according as exhaust or live steam is used, the term " live steam" being taken in its ordinary sense as indicating steam of about 80 pounds pressure. If practically all of the air is returned from the building, these figures will be raised to about 140, as the minimum, and possibly 200 cubic feet, as the maximum, per foot of pipe. Of course, the larger the building in cubic contents the less its wall and roof exposure per foot of cubic space, and con- sequently the less the loss of heat and the smaller the heater relatively to the cubic contents. In such buildings, used for manufacturing purposes, where the occupants are usually well scattered, an air change once in fifteen to twenty minutes represents the general practice, but in public and similar buildings this change is of necessity reduced to once in seven to twelve minutes. Owing to the increased loss of heat by leakage or ventilation under such conditions, and also to the demand for a slightly higher temperature than in the shop, the allow- ance is dropped to from 70 or 75 to 125 cubic feet of space per foot of pipe, for all of the air is taken from out-of-doors and low-pressure steam is usually employed. The great range in all of these figures must make evident the influence of the size, construction and uses of a building upon the size of the apparatus required, and show the necessity of extended experience for the proper designing of any system of heating and ventilation. 33 VENTILATION AND HEATING VALUE OF EXHAUST STEAM. Most important to every manufacturer is the complete utilization of his exhaust steam, for it usually has a value as a heating medium of very nearly 97 per cent, of ordinary high-pressure steam. It is obviously unwise to employ live steam for heating when exhaust steam is at hand or even at some distance, for the expenditure for the conducting pipe for such waste steam will almost always be warranted. In many systems of direct radiation it is more or less difficult to make use of the exhaust, but the Sturtevant Heater has been designed with this special purpose in view. It is, furthermore, arranged with one or more special sections, in which may be condensed the exhaust steam from the small engine which is usually provided for driving the fan. Although the total heat (measured in heat units) of exhaust steam and of live steam of 80 pounds is very nearly the same, the difference in actual tem- perature is such exhaust steam averaging about 220, while steam of 80 pounds is about 323 that there is a marked difference in the rate at which they give up their heat when enclosed in steam pipes across which air is caused to circulate. This rate of transmission is proportional to the difference in tem- perature between the steam within and the air outside the pipe, and, therefore, exhaust steam requires for the condensation of a given weight of steam in a unit of time a larger area of surface than live steam. Furthermore, exhaust steam being less dense than live, it must require a larger pipe to convey the same weight. The proper proportioning of the areas of steam -conducting pipes, according to the pressure, seldom receives sufficient attention. The accompanying table, No. 5, is therefore presented to show the amount of steam of given pressure that will flow per minute through pipes of various sizes with a loss of only one pound of pressure. From this may be easily determined with sufficient accuracy, the size of steam pipe required to conduct a given weight of steam of known pressure. In considering the introduction of a special engine for driving the fan of a heating apparatus, it should be clearly realized that a certain amount of steam being required for supply to the heater, the passage of that steam through the engine on its way to the heater entails very little loss in its heating power, so little, in fact, that the actual expense of driving the fan may be disregarded and the steam-engine cylinder may be looked upon as merely an enlargement of the steam pipe. Evidently this feature of this system has its influence on the relative cost of driving the fan by engine, or by electric motor, for, in the employment of the latter there is no incidental return whereby the cost of power is reduced. 34 VENTILATION AND HEATING TABLE No. S- OF WEIGHT OF STEAM IN POUNDS PER MINUTE THAT WILL FLOW THROUGH PIPES OF GlVEN DIAMETER WITH Loss OF ONE POUND OF PRESSURE. Initial Gauge Pressure in Lbs.perSq.ln. DIAMETER OF PIPE IN INCHES. LENGTH OF EACH =240 DIAMETERS. % 1 1% 2 2^ 3 4 5 6 8 10 1 1.16 2.07 5-7 10.27 15-45 25.38 46-85 77-3 "5-9 211.4 341-1 1O 1.44 2-57 7-i 12.72 I9-I5 3i 45 58-05 95-8 143.6 262.0 422.7 20 1.70 3.02 8-3 14.94 22.49 36.94 68.20 112. 6 168.7 307.8 496.5 30 1.91 3-40 9-4 16.84 25-35 41.63 76.84 126.9 190.1 346.8 559-5 40 2.10 3-74 10.3 18.51 27.87 45-77 84-49 139-5 209.0 38i.3 6i5-3 50 2.27 4.04 II. 2 20.01 3- i 3 49.48 9 r -34 150.8 226.0 412.2 665.0 6O 2-43 4-32 11.9 21.38 32.19 52.87 97.60 161.1 241.5 440.5 710.6 70 2 -57 4.58 12 6 22.65 34.10 56.00 103-37 170.7 255-8 466-5 752-7 80 2.71 4.82 13-3 23.82 35-87 58.91 108.74 r 79-5 269.0 490.7 791.7 90 2.83 5-04 13-9 24.92 37-52 61.62 H3-74 187.8 281.4 5I3-3 828.1 100 2-95 5-25 H5 25.96 39-07 64.18 11847 195.6 293.1 534-6 8626 120 3.16 563 i55 27.85 4i-93 68.87 127.12 209.9 3H-5 573-7 925.6 DETERMINATION OF FAN CAPACITY. In the case of a factory, or building of similar construction and uses, to be heated by the blower system, the matter of heating is usually considered of most importance, and, therefore, the exact average air change is first to be decided upon, a matter largely dependent upon sound judgment. As already stated, this ranges from fifteen to twenty minutes, according to circumstances. But no matter what the average time of change, certain exposed rooms should receive a larger volume of air than their proportional cubic contents would demand ; on the other hand, well- protected and interior rooms demand a much smaller supply. If all the rooms are not to be heated to the same temperature, a further correction is to be made. It is to be noted, however, that a stated increase in the air supply to a given room will not produce a proportional increase in its temperature. In the light of the preceding remarks upon the effect of ventilation on heating, it must be evident that, the temperature of the entering air remaining the same, if its volume be doubled the loss by leakage of air will be doubled also, while the 35 VENTILATION AND HEATING normal loss by conduction and radiation will remain the same, so long as the temperature of the room does not change. But naturally the room temperature will rise, causing a still further loss of heat by leakage, because of the higher temperature of the increased volume, whereby more than twice as many heat units escape per minute. On the other hand, the transmission loss will have become greater only .in proportion to the increased difference between indoor and outdoor air. It is, therefore, evident that some means is necessary by which special allowance may be made in the air volumes delivered to those rooms in which temperatures are to be maintained that differ from that assumed as the average of the building. By a process of reasoning, similar to that previously employed in discussing the effect of ventilation on heating, a series of factors may be determined which will aid in the ready solution of heating and ventilating problems in which a change of temperature is dependent upon a change in the air volume supplied. The process can best be explained algebraically, and then illustrated by some practical examples. If we designate by x the temperature of the entering air under certain conditions, and by y the difference between the temperature main- tained indoors and that existing out-of-doors, it is evident, upon the basis pre- viously employed, that the total losses by leakage and by transmission would be respectively represented thus : Leakage = -^- x x =y Transmission = X x = x y x If now, with the same entering temperature is should be desired to maintain a difference between indoors and outdoors different from y and expressed by z then the loses would be : Leakage = x x = z Transmission = x x x x z X But, whereas, in the first instance the transmission loss was indicated by x y the available supply for this purpose is now represented by x z. Whether this amount is sufficient will depend upon the relative values of y and z, and evi- dently the total supply in units necessary to meet the loss by transmission under the new conditions will be (xy) while the volume of entering air at the 36 VENTILATION AND HEATING _ same temperature as before will have to be - = - - times x z y (x z) that in the first case. The loss by leakage will, on the other hand, be altered in the proportion of due to the changed difference between indoor and outdoor temperature, further modified by the changed volume expressed by the proportion of v so that the total loss will be represented by X Z z . . z^ y Leakage = X -2 X v = 2 - = f~ y \ y X Z XZ y (X Z) For the sake of illustration let us now take the case of a factory in which the air supply at a temperatue at 140 is of sufficient volume to change that within the building every 16 minutes and to maintain therein a temperature of 70, the outdoor temperature being at 0., Under these conditions x = 140, y = 70 and Leakage = -~ X x = X 140 = 70 x y 140 70 Transmission = *- X x = X 140 = 70 If now, it be desired to maintain the building or any room within it at 80 which would represent z in the formula, then Leakage = - r x x = Q X 140 = 80 Transmission = -- X x = X 140 = 60 x 140 That is, 1.33 times as much air will be required to maintain an internal temperature of 80 as one of 70. It is evident that this is a relative value, and is not dependent upon the original time for air change, and may, therefore, be applied relatively even if the time of change is not known. Under the stated conditions, however, the air volume necessary to maintain a temperature of 80 would be equivalent to air change once in 12 minutes. 37 37944 2 VENTILATION AND HEATING The results of a series of calculations by this method, on the basis of a given volume of air at 140 being capable of heating the given building to various temperatures from 30 to 110 are represented by the accompanying curves (Fig. 4), from which may be read the factor to be employed for any given differ- ence in temperature between indoor and outdoor air, each curved line representing factors for any basis temperature at which the given volume at 140 will main- tain the building, the factor 1 applying when the basis temperature as indicated on the curve is to be maintained. For instance, if the heating apparatus is to be based upon the relative size required to maintain a difference of temperature of 70, all factors will be read from the curve marked 70, and the factor for any other difference, as 80, will be obtained by following up the vertical line above the temperature until it intersects the curve of 70 and then reading the value at the left. Of course, the factors hold only for the specified temperature of entering air, but similar sets of curves may be readily developed by the same method for other temperatures. As the curves are worked out for differences in temperature, it must be evident that to obtain, for instance, the factor for a basis temperature of 20 below zero outside and 70 inside, the curve for the total difference, viz., 90, must be used. If the contents of the various rooms of the building have been tabulated, the factors thus obtained may be most readily applied by simply multiplying by them respectively the contents of such rooms as are to be heated to the tempera- tures to which they correspond and then proportioning fan, pipe and flue area relatively to their corrected contents. Under the following illustrative conditions of contents and desired tempe r a- tures, with outdoor temperature of 0, the factors would be applied to make the apparent relation of contents as shown : CAPACITY OF ROOM DESIRED RELATIVE CAPACITY OF IN CUBIC FEET. TEMPERATURE. FACTOR. ROOM IN CUBIC FEET. 65,000 60 75 48,750 30,000 90 1.8 54,000 95,000 40 .4 38,000 45,000 70 1. 45,000 50,000 50 .55 27,500 75,000 80 1.33 100,000 360,000 313,250 Hence, if it is estimated or known that a given air change will heat the entire structure to 70, it will require only ttM** = .87 as much air supply per unit of time to accomplish the desired results as above specified. The vast difference 38 VENTILATION AND HEATING 10 . 20" . 30 4O 5O 60 70 60 90 100" 110 120 130" 140 DIFFERENCE BETWEEN INDOOR AND OUTDOOR TEMPERATURE FIG. 4. FACTORS FOR PROPORTIONING AIR SUPPLY. 39 VENTILATION AND HEATING between requirements at high and low temperatures is evident in the factors for 40 and 90, the latter being 4.5 times the former. If carried to its limits this method of calculation will show no air change to be required at zero and an infinite change to maintain the same temperature as that of the entering air. Of course, it must be understood that corrections for exposure and materials of construction should be applied wherever possible, and that these factors are only to be employed in approximate work. The curves are, however, in- tended to cover average conditions, subject to individual corrections for various rooms, and as such indicate the relative air volumes required under equivalent conditions of exposure and construction. This, then, is the method of determining the fan capacity required where the calculations are based merely upon the times of air change the system generally adopted for factory and similar work. For public buildings and the like, where ventilation is the vital feature of the system and the number and activity of the occupants can be definitely determined, the total air supply is to be based upon the predetermined provision per head. The general allowances for various classes of buildings have already been given so that it is only necessary to decide upon the allowance to be made in the given case under consideration and multiply this by the total number of occupants. To the volume thus determined, must be added the amount to be provided for corridors, cloak and toilet rooms, and for apartments not intended for regular occupancy. The aggregate volume to be supplied should obviously be made sufficient for the maximum requirements and the system so arranged that proper distribution will be secured where the mini- mum supply is provided. SELECTION OF FAN. The capacity of a fan is evidently measured by the number of cubic feet of air it can deliver per unit of time at a stated speed. The efficiency of the type of fan, therefore, enters as a determining factor in deciding upon its size. In any extended system of heating and ventilation of which the fan forms an element, it is necessary that the peripheral type of dis- charge be adopted in order to overcome the existing resistances of ducts and flues. The disc or propeller type, which forces the air in lines parallel to its shaft, is very inefficient where such resistances exist ; but a fan wheel, either cased or open and delivering the air at its periphery in a more or less radial direction, is capable of meeting all requirements. It is evident that the primary factors entering to determine the capacity of a fan of given type, are its size and the speed at which it is driven. The volume of air delivered by a fan practically varies directly with the speed, while the air pressure created changes in propor- 40 VENTILATION AND HEATING tion to the square of the number of revolutions, and the power required to drive the fan varies in the ratio of the cube of the speed. That is to say, doubling the speed of a fan doubles the volume delivered (which is the measure of its capacity), increases the air pressure created to four times that previously existing, while the power required rises to eight times that at half speed. These facts should be clearly borne in mind in the selection of a fan, and, so far as circumstances will permit, a large fan operating at moderate speed should be chosen, as a means of not only decreasing the power required but of also reducing the losses due to excessive friction in the ducts incident to the move- ment of air at higher pressure. For factory and mill work the fan may approach nearer to the minimum size, for higher air velocities are not only permissible but frequently desirable to force the air long distances, while the usual presence of an experienced engineer ensures more frequent attention where the fan is constantly operated at high speed. In the schoolhouse, the theatre, the church, and similar structures, where a much more complete system of air distribution is necessary and where only low velocity currents are permissible, the fan should be of the maximum size, capable of delivering the required volume of air at the least practicable speed. To summarize, it is necessary in the selection of a fan to first determine its required capacity, to then decide upon the type to be adopted, and to finally select the size best adapted to the given requirements as largely influenced by the maximum speed allowable. Such selection cannot be alone based upon published tables of fan capacities, for even with the type of fan clearly defined there is opportunity for disastrous mistakes in deciding upon speed and in making the allowances that are necessary for the loss in volume moved, due to the resistances encountered in passing through the heater and through the distributing ducts. The tendency, from a commercial standpoint, is strongly toward the selection of too small a fan and to this fact is due the failure of many of the earlier plants installed under the specifications of those who possessed but limited experience in these matters. Therefore the selection of the type of fan and the determination of its size should be left to parties fully qualified to decide upon this important factor in the heating and ventilating system. GENERAL ARRANGEMENT OF THE STURTEVANT SYSTEM. As already indicated, the Sturtevant System of Heating and Ventilation compre- hends only that method by which ventilation is secured under plenum conditions, that is, where the air is forced into, rather than exhausted from, the building, and comprises in its entirety a steam heater or heaters, a fan driven by some type of 41 VENTILATION AND HEATING motor and a system of ducts and flues through which the air is forced to the various apartments of the building. The size and arrangement of these ducts and flues, as well as the location of the apparatus, is directly dependent upon the con- "struction and use of the building. Although several States now legally require adequate ventilation in factory buildings, yet it must be admitted that in the introduction of the Sturtevant System the owner's first motive is usually mercenary rather than humanitarian. But the Sturtevant System fortunately possesses this particular feature, con- sidered solely as a heating system, namely, that in order to heat successfully it is necessary to supply a volume of air sufficient at the same time to thoroughly ventilate any ordinary factory structure where the processes are no more than ordinarily objectionable. The introduction of the Sturtevant System is, therefore, divided between two great classes of buildings. First, where heating is pre-eminent and ventilation is merely incidental, and Second, where the system of ventilation is of primary importance, and heat- ing is necessarily combined with it for successful operation rather than introduced as an independent system. To the first class belong almost exclusively all manufacturing buildings, store- houses, drying-rooms, exposition buildings, and some offices and stores. In the second class are those buildings in which specially objectionable pro- cesses are carried on, hospitals and asylums, all halls of audience (including theatres, churches and schools), and stores and offices not included in the first class. The enterprising manufacturer is quick to appreciate his financial interest in the provision and maintenance of an atmosphere in his factory that exhilarates rather than wearies his employees ; for a direct monetary return can be shown in the improvement in quantity and quality of work resulting from the introduction of this system with pure air and a comfortable temperature. Considerations of economy and the before-mentioned idea of the owner, that heating is the pre-eminent feature desired in the application of the system in a factory, have much to do with the location of the apparatus. To secure economy in heating where improved ventilation does not enter into the question, the ap- paratus is frequently arranged so as to take its air supply entirely from within doors, thereby simply turning the air over and over within the building. There is, however, an incidental leakage resulting in a degree of ventilation considerably in excess of that occurring with any system of direct steam heating. To this end, in a one-story structure the apparatus should be placed as near the centre as pos- sible, so that the air may be drawn back to it from all sides. 42 VENTILATION AND HEATING Dependent upon the character and construction of the building, one of two general methods of distribution may be adopted. The first and most common is by a more or less extended system of metal ducts or pipes, almost universally constructed of galvanized iron on account of its durability. Such a system is the only one practicable in wooden structures. In brick buildings, particularly those of two or more stories, brick ducts and brick vertical flues are the most conven- ient, and, as usually applied, do not encroach upon valuable interior floor space. The one -story structure with brick, wood or metal sides, with sloping roof surmounted by skylight or monitor, forms to-day the model for the foundry and the machine, boiler or blacksmith shop, while its use is rapidly extending to other trades. In such a building some arrangement of galvanized iron distribut- ing pipes is compulsory, for the brick duct and flue become too expensive pro- portionally to the cubic contents to be heated. In comparatively narrow wooden structures, where it is a question of galvan- ized iron pipe or nothing, the main distributing pipe extends lengthwise of the basement and there connects with risers carried up alongside of the supporting columns of the building, from which the air is discharged towards the walls through properly located outlets about 8 or 9 feet above each floor. The ideal installation of the Sturtevant System is in the three or four-story brick factory of the type of the ordinary cotton mill, where the heated air is con- ducted from the apparatus through a duct in the basement to the bases of special pilaster flues located upon the outside at regular intervals along one side of the building. The horizontal duct constructed of brick, usually extends along the in- terior of the basement wall, and is provided with either a flat or arched top of approved and air-tight material, or is made quadrant in form, thereby securing for a given expenditure of material the maximum area for the passage of air. At distances varying from 40 to 75 feet, the piers between the windows are carried out and form the pilaster flues which receive the heated air from the duct and discharge it above the head line on each floor. Most prominent among the buildings in which the ventilation may be con- sidered of primary importance are those in which persons remain for several hours closely seated and practically inactive, as is the case with an audience in a church or a theatre and with the pupils in a schoolroom. Here the per capita air space in the room is at its minimum. In the best modern schoolroom there is usually an allowance of 2 50 cubic feet of space per occupant ; but in many theatres and halls this figure is reduced as low as 75 to 100 cubic feet to each person. In the ordinary schoolroom a supply of 30 cubic feet per head per minute would necessitate changing the entire volume of the room once in about eight 43 VENTILATION AND HEATING minutes, while in a hall with only 75 cubic feet of space for each member of the audience such a supply of air would require a complete change once in every two and one half minutes. It is difficult, without extreme care, to so introduce such an excessively large volume of air under these latter conditions without creating objectionable draughts about the occupants. In this climate a perfect system of heating and ventilation applied to a build- ing of the aforementioned class, should, First, maintain within each room a mean temperature of 70 F., irrespective of changes in external temperature, with a total variation of not over 2 or 3 above or below this mean at a given level in any occupied portion of the room. Second, supply to the room, under all conditions of indoor and outdoor atmosphere, a constant predetermined volume of air, and deliver it without creating objectionable draughts and in such a manner as to be thoroughly and efficiently distributed throughout the apartment. This second requirement may even be so exacting as to demand a constant indoor temperature, with variable supply of air proportioned to the varying number of persons occupying the room. Assuredly, with no arrangment or device can the air supply be more readily proportioned to the requirements than with the Sturtevant System. Doubtless at the present time more attention is being given to improvement in schoolhouse ventilation than to that of any other class of structures ; and fortunately the ordinary schoolhouse, with its brick partition walls, presents a most excellent opportunity for the economical placing of the necessary flues, for they may be grouped along the interior walls and provided with inlet openings about 8 feet above the floor and vent openings at floor level. The hall and the church are in reality but enlarged schoolrooms as regards their treatment by the blower system. The same vital requirement holds : that the temperature must be maintained independent of volume of air admitted, while the difficulty of satisfactorily admitting the required air supply is increased by the closer seating of the audience. The theatre presents far more complication than the hall ; its three parts stage, auditorium and lobbies may at one moment be essentially one and the next be rendered practically independent. The auditorium is usually thoroughly protected by the lobbies or the walls of adjacent buildings, so that the heat loss is reduced to a minimum, and during a performance it becomes a question of cooling rather than of warming the occupants. In some cases the air has been supplied entirely through perforated ceilings, whence it passes down over the persons of the audience and escapes through a multitude of openings in floor and risers. This unnatural movement of the air 44 VENTILATION AND HEATING against its own impulse must be facilitated by exhaust fans connected to the area beneath the floor in addition to the plenum fans for forcing in the fresh air. The rapid improvement in theatre ventilation certainly indicates that the enterprising manager sees therein another inducement to the theatre-going public to patronize his individual house in preference to one where the air is foul and oppressive, although the dramatic attraction may be equally good. The requirement of large air volume per capita in hospitals and asylums, particularly in contagious wards, necessitates positive and ample means which can only be satisfactorily met by the fan, standing as it does, capable, according to its size, of supplying any amount of air required. The store with its extended floor areas, and the office building with its multiplicity of small rooms, call for arrangements peculiarly their own. In fact, the ready adaptability of the Sturtevant System to diverse conditions forms one of its salient features. Many illustrations of its application are presented in succeeding pages; the preceding brief outline being here given only to indicate the general scheme of application. DOUBLE DUCT SYSTEM. The varying exposures of the rooms or a school or other building similarly occupied, require that more heat shall be supplied to some than to others. The sunlit, southerly room, perhaps still more favored by being over the boiler, may be kept perfectly comfortable with a supply of heat that perchance will barely maintain a temperature of 50 to 60 F. in a room on the opposite side of the building, exposed to high winds and shut off from the warmth of the sunshine. With a constant and equal volume of air supply to each room, it is evident that its temperature must be directly proportional to the cooling influences within and around the room, and that no building of this character is .properly heated and ventilated where the temperature cannot be varied without affecting the air supply. To this end, air of a given temperature may be conducted to the base of each flue and there tempered to a degree suitable to the requirements of the room supplied. Two methods appear : The older arrangement consists in heating the air by means of a primary coil, at or near the fan, to about 60 F., or to the minimum temperature required within the building. From the coil it passes to the bases of the various flues, and is there still further heated by secondary or supplementary heaters, one or more to each room. Under certain conditions the distribution ducts may be omitted, and the entire sub-basement made to serve as a large plenum chamber containing air under slight pressure heated to about 60 F. by the main coil. 45 VENTILATION AND HEATING With the second and more recent method a single heater is employed, the supplementaries are discarded, and all of the air is heated to the maximum required to maintain the desired temperature in the most exposed rooms, while variety in temperature of air supplied to the other rooms is secured by mixing with the hot air a sufficient volume of cold air at the bases of the respective flues. This result may be best accomplished by designing a hot blast apparatus so that the air shall be forced rather than drawn through the heater, and by providing a by-pass through which it may be discharged without passing across the heated pipes. This discharge for the unheated air is usually made above and separate from the heater pipes. Extending from the apparatus is a double system of ducts, almost universally constructed of galvanized iron and suspended from the ceiling. At the base of each flue is placed a mixing damper which is controlled by chain from the room above, and so designed as to admit either a full volume of hot air,- a full volume of cold air, or to mix them in any desired proportion without affecting the resulting total volume delivered to the room. Where perfect and continuous regulation, independent of the teacher, is desired, the damper should be operated by a thermostat in the room with which the flue connects. The hot and cold system, as this double duct is familarly known, accom- plishes at less expense, with greater rapidity and equal certainty, the results obtained by the more complicated method previously described, and is being extensively introduced in the modern schoolhouse wherever the blower system is applied. As ordinarily installed, the hot air and the cold air connection to each mixing damper are of equal area so that whether the air be hot or cold or a mixture of the two, its volume will remain constant. An accurate calculation of the resulting temperature when two known volumes of air of given temperatures are mixed must take into consideration the temperature, weight and humidity of these volumes ; but for rough estimating and for purposes of comparison the difference in weights and humidity may be disregarded. It then becomes merely a question of averaging of the simplest kind. Thus, for instance, if of a stated resulting volume, 4 parts were introduced at a temperature of 30 and 6 parts at a temperature of 120, the calculation would be merely (4 X 30) + (6 X 120) = ^ In this manner the accompanying diagram (Fig. 5) has been laid out simply to illustrate the relative mixtures and resulting temperatures under a given set of conditions. As a fair average for schoolhouse work, 120 has been taken as the initial temperature of the hot air in its relation to various proportional mixtures 46 VENTILATION AND HEATING 1 120 100 90 80 u. 70 60 50 30 20 10 -20 10 7 6543 PARTS OF COLD AIR IN MIXTURE 34567 PARTS OF HOT Am IN MIXTURE 10 FIG. RESULTING TEMPERATURES OF VARIOUS MIXTURES OF HOT AND COLD AIR. 47 VENTILATION AND HEATING with cold air at 30 up to 120 ; of course the terms " hot " and " cold " become here distinctly relative ; in fact, they always are. The vertical lines upon the diagram represent the relative proportions of hot and cold air as indicated by the figures at the bottom, while the horizontal lines serve as measures both of the initial temperature of the cold air and of the resulting temperature of the mixture, which latter may be read from the diagonal line ending in the given initial temperature of the cold air. For instance, the temperature of a mixture of 3 parts of cold air of 20 temperature and 7 parts of hot air of 120 (the basis for the diagram), may be read at the intersection of the diagonal from point 20 on the left and the vertical from the point 3 for cold air and 7 for hot air on base line below. As previously stated, the correction for change in weight due to change in temperature has not been applied, but the diagram shows, nevertheless, the results of the given conditions in a manner sufficiently accurate to facilitate ready comparison. Of course the cold air figures refer to the temperature of the air as it passes through the mixing damper. What its temperature might have been before entering the apparatus must depend largely upon the arrangement of the system and the total amount of cold air passing through the apparatus at the time. DISTRIBUTION OF AIR. Thorough distribution of the air supplied by any system of ventilation is necessary, not only for the best results in the matter of dilution, but also to absolutely prevent the possibility of objectionable draughts. In halls of audience, where the occupants are at rest, any slight inequality in the distribution is particularly noticeable ; while in the workshop, where all are in motion and not in close contact with each other, less refined arrangements will give satisfaction. Experiment has shown that a velocity of air less than nineteen inches per second is not perceptible to the senses, and that an air movement as high as three feet per second is not objectionable. Perception of draughts depends largely, however, on the temperature and humidity of the air in motion as compared with that normal in the room. It is evident, therefore, that special care should always be exercised, in order that no current having a velocity in excess of three feet per second, or one hundred and eighty feet per minute, be allowed to come in contact with the body. The same method of distribution is not applicable in all cases. On general principles, it may be asserted that, wherever the air is cooled in its progress or passage through a room, that it will best serve its purpose as a means of heating and ventilating if it be admitted to the room at a point moJ: distant from the 48 M VENTILATION AND HEATINGS outer walls. This point of discharge should be at least eight feet above the floor, and the air movement should be directly toward the outside walls. Such an arrangement is very easy of introduction in a building having interior parti- tion walls, as an office, a dwelling, or a school building, for the flue may be constructed within or against these walls. Thus located, the air discharged from the outlet passes in a constantly spreading volume above head level toward the exposed walls, where, becoming slightly cooled, it slowly settles to the floor. To complete the circuit and fulfil the design, the ventilating register should be in the same inner wall as the supply opening, but close to the floor. There is thus induced toward this outlet a return flow of the air in a well-distributed mass. The currents are, in reality, stratified, the lower one serving to take up the emanations from the lungs of the occupants as its sweeps slowly across them directly towards the ventilating register. In factory heating no ventilating flues are provided, as there is always sufficient leakage of air around windows and through porous walls; but the air should, nevertheless, be introduced above head level. In the case of theatres, and of most halls and churches, the large number of occupants serves, by the animal heat generated, to visibly increase the tempera- ture of the air admitted. The conditions are, therefore, exactly the reverse of those where the air is cooled in transit, and the best results are obtained by causing the air movement to be directly upward, or, as in the case of some recent installations, directly downward, with the air supply through the ceiling. Minute sub-division of the supply is an absolute necessity when it is admitted through the floor, and with either the upward or the downward method the design is to secure individual ventilation, so far as may be practically possible. The details of construction necessary to secure the proper air move- ment for these various classes of buildings will be made evident in the illustra- tions which follow. ARRANGEMENT AND CONSTRUCTION OF DUCTS AND FLUES. The arrangement of the system of ducts and flues within a building must, of necessity, be dependent upon the method of distribution adopted, which in turn will be largely influenced by the construction of the building. If of brick, the flues may be most readily and economically built in the walls as the building is erected. Such a procedure, however, presupposes the selection of the system before the building plans are completed. As natural and necessary as this may seem, it is lamentably true that such decision is very frequently delayed until the building is under way. 49 mm VENTILATION AND HEATING Under such circumstances, it is usually necessary to provide for the distribu- tion through metal ducts, whose position is seldom what it should be, owing to the exigencies of architectural features. In fact, the day has not yet arrived when hygienic demands always take precedence over architectural symmetry and beauty. Not that harmonious architectural composition cannot be preserved when proper provision is made for heating and ventilating flues, but that the work of the architect is too frequently schemed and the drawings completed without adequate consideration of the ventilating system to be adopted. It is surprising how successfully flues can be introduced without marring the general effect, for it is a simple matter to work them in as false columns, pilasters, beams, or cornices, or to introduce perforated ceilings, without attract- ing attention. In an old building metal ducts and flues are almost a necessity, the material employed generally being galvanized iron. When ducts are to be placed under- ground, they should be of 1 brick for the larger sizes, while glazed tile pipe will serve for smaller ones. Flues which in matters of ventilation are generally classed as vertical air passages in distinction from ducts, by which name are designated the horizontal conduits should always be smoothly finished inside, and where the expense will permit, it is wise to line their interiors with sheet metal, either tin or galvanized iron, or with special terra-cotta flue linings which are made for the purpose. So far as possible the flues should be banked together for economy in con- struction, but independent flues should be provided for individual rooms, to insure equality of distribution, except where they are large, as in the mill and factory. With this arrangement a heating flue for the first floor may readily be stopped off above the outlet opening and employed as a ventilating flue from the floor above. It is best to carry all ventilating flues separately, above the roof, although very good results may be obtained under the plenum system, where they simply discharge into the attic, from which escape is provided through a cupola or louvered windows. If the complicated nature of the building demands that an exhaust fan be used, it should be directly connected with the flues. An exhaust fan simply drawing from the attic space and dis- charging out of doors will prove very inefficient, owing to the ease with which a portion of its supply will find its way, by leakage, through the roof rather than be drawn from the rooms below. As a result, the fan performs only a part of the definite duty assigned to it, and the amount of air which should be withdrawn from the rooms is so seriously reduced as to decidedly impair the ventilation. 50 VENTILATION AND HEATING Too much care cannot be taken in the design and construction of a system of ducts and flues. Owing to the small scale upon which the general scheme is, in most cases, necessarily shown, and the general lack of detail drawings for individual features, the galvanized iron worker and the mason are usually left, to a considerable extent, to their own devices to accomplish the desired results. This may be well enough in the case of men experienced in this line of work, as is particularly the case with those employed continuously on galvanized iron work by large and established heating and venti- lating concerns. But the local tinsmith and the ordinary mason are very apt, from inexperience, to fail to properly construct such work. The disastrous effect of sudden turns must be thoroughly realized, and wherever a change in direction is necessary, it must be made with as generous a curve as possible. In galvanized iron piping, " stove-pipe elbows," so-called, should always be avoided, and turns of direction of 90 constructed, FIG. 6. in the case of round pipe, radius of curvature of the to the diameter of the pipe. This proportion of radius round or rectangular. A great source sistance often re- pipe squarely into the branch nipple attached to the pipe of the change in all as clearly shown the main pipe is is taken out, and very gradual. It is piping to make this FIG. 7. with at least five pieces, and with the inner side of the elbow at least equal Such an elbow is represented in Fig. 6. to size holds whether the pipe be of unnecessary friction and undue re- sults from the butting of a branch the side of the main pipe. Instead, should be cut into and securely at an angle of 45, and the remainder direction made by using a half elbow, in Fig. 7. It is to be noted that reduced in area after the branch that this reduction, or taper, is the usual practice in well made taper equal in width to a sheet of galvanized iron, which, with the usual thirty-inch-wide sheet, will give a net length of twenty -eight inches when the pipe is put up. The same method should be employed with regard to reductions in the size of all forms of rectangular ducts. 51 VENTILATION AND HEATING Wherever a branching or division of the main pipe is to be made, and even in cases where a relatively large branch is to be taken from the side of the main pipe, the piece divide the air air volume angle, and its direction outlet, is il- pipe. Rect- same gen- easily ap- it should be tinue in the direction at in area be- should be so constructed as to proportionally currents ; that is, in such a way that the is practically split by the opposing acute easily, but positively, compelled to change of movement. Such a branch, or divided lustrated in Fig. 8, as applied to a round angular pipe should be treated upon the eral principle, which is here much more plied. Fig. 9 indicates the form in which constructed where one portion is to con- same direction and the other turn to a right angles. In reality, the reduction yond the branch is made in the process of taking out the branch, and by its arrangement serves to catch and deflect the requisite amount of air. Pipe of this form and construction is largely employed in public building and schoolhouse work, for the purpose of distribut- ing the heated air from the apparatus to the bases of the various vertical flues. When thus employed, it is usually suspended close beneath the basement ceiling, and made of such depth as to allow ample head room, thus forming as a rule a com- paratively flat pipe. With all due regard in the design to the unequal resistances of ducts and flues of different areas and lengths, it is always best to additionally provide, in the main supply system, the means of primary permanent equalization of air volumes to the various flues. To this end, all such branches as that shown in Fig. 9 -- should be provided with light and short flap dampers, easily adjusted from outside the pipes FIG. 9. and permanently held in place by set-screwing the rods when turned to the proper position. This damper is very clearly indicated in the cut. In small pipes, a mere extension of flexible sheet iron from the dividing angle will serve the purpose, and may be adjusted through a handhole in the pipe, which should be provided with a slide. 52 VENTILATION AND HEATING The same principles hold in the construction of brick ducts and the intro- duction of tile pipes. The difficulty in brickwork generally lies in the un- willingness of the mason to introduce curves, because of the extra care required in laying them. But misproportioned brick ducts, and the lack of proper adherence to drawings, has resulted in serious trouble in many cases. A typical construction is presented in Fig. 10, and it is to be noted how easily the air is deflected into the side branch. The tops of such ducts may be arched, as shown, or may be covered with properly spaced T irons, between which bricks are laid and thoroughly bedded in mortar. DIMENSIONS OF DUCTS AND FLUES. The area of a flue or duct is obviously determined by the volume of air destined to pass through it and the permissible or desirable rate of flow. From a consideration of the fact that the losses due to friction of air in its movement through pipes increase as the square of the velocity, so that doubling the velocity increases the friction four- fold, it would at first appear that the ultimate object in any design should be to move the air at the lowest possible velocity, but the accomplishment of such an object obviously demands ducts of vast size. It is plainly evident, however, 53 'VENTILATION AND HEATING that the interest account on the increased cost of such ducts may readily exceed the saving in power attained by reducing the rate of air movement. It is further true that, in any successful system of ventilation, it is necessary, in order to secure positive circulation, that the velocity and pressure of the air should not be allowed to fall below a prescribed minimum. But, most important, as render- ing the general question of velocities of still less importance from an economical TABLE No. 6. OF THE LOSSES IN PRESSURE AND HORSE POWER DUE TO FRICTION OF AIR PASSING THROUGH PIPES. Diameter of Pipe in Inches. Loss OF PRESSURE AND HORSE POWER. VELOCITY OF AIR IN FEET PER MINUTE. 1OOO 12OO 14OO 16OO 1800 2000 2200 24OO 2600 1 X 2164.76 4653 13. 132-73 11.52 33. 855-30 29 25 53, 2206.19 46.97 X 143-H. 11.96 -X 881.41 29.69 X 2248.01 474 14. 153-94 12.41 34. 907.92 30-13 54. 2290.23 .17.86 /2 165-13 12.85 -X 934.82 30-57 X 2332.83 48.30 15. 176.72 13.29 35. 962.11 31.02 55. 2375-83 48.74 # 188.69 13-74 X 989.80 31.46 -X 2419.23 49.19 16. 201.06 14.18 36. 1017.88 31.90 56. 2463.01 49-63 X 213-83 14.62 X 1046.35 32-35 -X 2507.19 50-07 17. 226.98 15-07 37. 1075.21 32-79 57. 255I-76 50-51 X 240-53 I5-5 1 X 1104.47 33-23 X 2596-73 50.96 18. 254-47 1595 38. 1134.12 33-68 58. 2642.09 51.40 # 268.80 16.40 X 1164.16 34.12 X 2687.84 51.84 19. 283.53 16.84 39. 1194.59 34-56 59. 2733-98 52-29 X 298.65 17.28 X 1225.42 35-oi -X 2780.51 52.73 20. 314.16 17.72 40. 125664 35-45 60. 2827.74 53-17 -X 33o.o6 18.17 .x 1288.25 35-89 X 2874.76 53-62 60 VENTILATION AND HEATING WEIGHT OF GALVANIZED IRON- PIPE. As already stated, galvan- ized iron is almost exclusively employed for the making of large pipes, ducts and flues for the conduction of warm air. Its non-rusting qualities, and the large size of the sheets in which it may be purchased, make it, by all means, the best suited material for this purpose. Although straight, round pipe is frequently sold by the running foot, the ordinary practice in work at all complicated, as in the case of a heating and ventilating system, is to base the price upon the weight, the rate being at a given amount per pound. As prices have to be made in advance, it is evidently very necessary that one should be able to accurately estimate with comparative ease from a drawing the amount of material required. To aid in such calculations Table No. 10 has been prepared, giving not only the weight of the galvanized iron per square foot, but also the weights per running foot for round pipe and the weight of elbows of corresponding sizes. This table may be relied upon as giving the maximum weight, due allowance having been made for laps and trimmings, as well as for rivets and solder ; the general waste, for obvious reasons, cannot be included. The elbows are of the. standard type previously described, having the internal radius of curvature equal to the diameter of the pipe itself. All of the weights are based upon the recently-adopted schedule of galvanized iron, in which the weights per square foot to some extent vary from those previously existing. In ordinary heating and ventilating practice, it is customary to make round pipe in its various sizes upon gauges as follows : under 9 inch, No. 28 gauge ; 9 to 14 inch, No. 26; 15 to 20 inch, No. 25 ; 21 to 26 inch, No. 24; 27 to 35 inch, No. 22 ; 36 to 46 inch, No. 20; 47 to 60 inch, No. 18 ; and all sizes above 60 inch of No. 16 gauge. If the pipe is made much lighter, particularly in the larger sizes, it will not keep its shape when laid horizontally, thereby seriously affecting the tightness of the joints and decreasing the area. The common practice is to make rectangular pipes of the same gauge as round pipes having an equivalent area, but under certain conditions, as in the case of thin, flat pipe for overhead distribution in a basement, bracing is necessary to prevent the top and bottom from sagging even with heavy gauges. There- fore, with the bracing, gauges lighter than the ordinary may be used. In calculating the weight of rectangular pipe, its superficial area, i.e., its perimeter in feet, multiplied by its length in feet, is taken as the basis, and special 'shapes are figured in a similar manner. The laps in rectangular pipe require more stock than in round pipe, and, therefore, from ten to twenty-five per cent, is added, according to the character of the pipe, to allow for this excess of material and for the weight of the necessary bracing and ribbing. 61 VENTILATION AND HEATING TABLE No. 10. OF THE WEIGHT OF ROUND GALVANIZED IRON PIPE AND ELBOWS. Gauge and Wt. Sq. Ft. Diam. of Pipe. Area Sq. Ins. Weight Running Ft. Weight of Full Elbow. Gauge and Wt. per Sq. Ft, Diam. of Pipe. Area Sq. Ins. Weight per Running Ft. We f t Full Elbow. 3 7-i o-7 0.4 38 II34.I lS.2 139-4 4 12.6 i.i 09 39 1194.6 I8. 7 146.0 No. 28 5 19.6 1.2 1.2 40 1256.6 152.9 0.78 6 7 28.3 38.5 1.4 1-7 2-3 No. 20 42 1320.3 I3S5-4 19.6 2O. I 160.7 I6S.6 8 50-3 I. 9 2.9 1.66 43 1452.2 2O.6 176.7 9 63.6 2.4 43 44 1520.5 21.0 185.0 10 78.5 2 -7 5-3 45 1590.4 21-5 J 93-4 No. 26 ii 95-o 2-9 6.4 46 1661.9 22.0 202.2 12 113.1 3-2 7-6 0.91 13 H 132-7 153-9 3-4 3-7 8.9 10.4 47 48 49 J 734-9 1809.6 1885.7 29.2 29.8 3 4 274-3 286.6 298.8 15 1767 4-5 13-5 50 1963-5 31.0 309-9 16 201. 1 4-7 15.1 51 2042.8 31.6 3225 No. 25 17 227.O 5.0 17.0 5 2 2123.7 32.2 335-i 1.03 18 254-5 5-3 19.1 No. 18 53 2206.2 33-o 349-7 19 283.5 5-6 21.4 2.16 54 2290.2 33-6 363.4 20 314.2 6.0 23-9 55 2375-8 34-4 377-2 21 3464 7-o 29.6 56 2463.0 34-9 390-7 22 380.1 7-3 32-3 57 2551-8 35-6 405.1 No. 24 23 4I5-5 77 35-6 58 2642. i 36.1 418.8 1.16 24 25 452-4 490.9 8.0 8-3 38.6 41.7 59 60 2734.0 2827.4 36.7 37-4 448.6 26 530-9 8-7 45 i . n cfio T 27 572.6 10.9 59-i I 62 2922.5 3019.1 40.7 47-5 59'7 589-0 28 29 6I5-7 660.5 11.4 ii 8 64.2 68.6 63 64 3"7-3 3217.0 48.3 49.1 608.6 628.5 No. 22 30 31 706. 9 754-8 12.2 12.6 73-4 78.3 No. 16 65 66 3421.2 49-8 50-5 647.4 666.6 1.41 32 804.3 I 3 .0 83" 4 2.66 67 3525-7 687.4 33 855.3 13-5 88.9 68 363 1 -7 52.1 708.6 34 907.9 139 94-3 69 3739-3 52.8 728.6 35 962.1 H-3 99-9 70 3848-5 53-6 750.4 No. 20 36 1017.9 17.2 124.4 3959-2 54-3 771.0 1.66 37 1075.2 17.8 131.4 72 407I-5 55-1 793-4 62 VENTILATION AND HEATING MIXING DAMPERS. With the advent of the hot and cold or double duct system there arose the necessity of a simple contrivance to coincidently regulate the volume of air discharged from the two ducts. Two methods of regulation appear: first, that by which full volumes of cold air and of warm air are alternately admitted; and second, that by which a damper is so constructed and adjusted as to permit the air of the two temperatures to produce a constant mixture of the desired temperature. If, by the first method, the alternations are sufficiently rapid, the room is maintained at practically a constant tem- perature, but if less frequent the tendency is toward fluctuation between extremes, although the proper average may be main- tained. Obviously, the first type of damper is impracticable for operation by hand, for it would require constant attention. For hand regulation the second type must, therefore, be adopted ; and, for perfect action, it must so admit the air volumes relatively to each other, that one shall be decreased proportionally as the other is increased, and thus cause the volume to continue constant. This requirement is met in the Sturtevant mixing damper, which, being of cylindrical form, of necessity fulfils this function. As ordinarily arranged for hand regulation, it is shown in Fig. 1 1 , in connection with a system of overhead ducts suspended just below the basement ceiling. The damper proper swings in a cast iron frame, which may be bricked into the wall, and to which the double system of ducts may be con- nected. From the cylinder, which is pivoted as shown, there extends up the flue a chain, which, after passing over a guide pulley, is conducted into the room at some three or four feet above the floor, there to be operated at the will of the occupants. When the air is conducted beneath the basement floor, the arrangement of ducts and damper is as shown in Fig. 12. Under these FIG. 11. FIG. 12. VENTILATION AND HEATING conditions proper manholes should be provided to permit of access to the ducts. Although the temperature of a given apartment may, by such means, be main- tained very near a stated temperature, the mixing damper may, under certain conditions, require such attention that the desirability of some other than -$- human agency may seem desirable for its operation. This part is played, and most perfectly too, by the thermostat, which, operating under the influence of the variations in temperature of the room, acts to produce converse action of the mixing damper. That is, as the room tempera- ture increases, the volume of cold air admitted is increased, while the warm air is correspondingly decreased. When regulation of temperature is to be secured by a maintained mixture of the hot and cold air, the type of damper previously illustrated is employed. In Fig. 13 is represented such a damper operated gradually by a thermostat, acting through a system of levers. With such a type of damper, it is possible to supply, through the cold air duct, air that has acquired no heat other than that taken up in its passage through the duct to the damper. But, if so supplied, the damper must be capable of shutting it off com- pletely, if occasion demands that a full supply of hot air only shall be delivered to the room to maintain the desired temperature. This is attained in the Sturtevant mixing dampers by packing the cylinder with felt in such a manner as to prevent all leakage of cold air when closed against its supply. For intermittent operation the type of damper shown in Fig. 14 is frequently employed. This consists mereiy of two straight butterfly dampers set at right angles to each other, so that when one is closed the other is open. Natu- rally with a damper of this description, VENTILATION AND HEATING operating to alternately admit cold and warm air, the relative temperature of the cold air should be only a little below that of the room to which it is supplied, for otherwise too sudden cooling and objectionable draughts would be caused. It is, therefore, necessary under these conditions to provide, in con- nection with the main apparatus, a tempering-coil through which all of the air shall pass, and from which volume the supply for the so-called cola-air duct shall be taken. A damper of this type is not desirable for gradual adjustment where a constant mixture is maintained ; first, because it is inherently incapable of keeping the total volume constant with the varying relative volumes of hot and cold air ; and second, because, as ordinarily constructed, it does not shut tight against the cold air supply. ADVANTAGES OF THE STURTEVANT SYSTEM. The advantages of the Sturtevant System, although incidentally mentioned in the preceding pages, may here be summarized under two main heads r. First, adaptability and convenience. Second, efficiency and economy. The early consideration of the system before the plans of the building are completed has, of course, much to do with its adaptability and the convenience with which it may be introduced. The centralizing of the entire heating surface in a single room and within a single sheet-iron jacket avoids all danger by fire, prevents the possibility of damage by leakage, and removes all anxiety regarding the freezing incident to isolated coils. A single valve serves to control the temperature of all air admitted to the building, so that the thoroughly installed system, with its governed engine, self -oiling devices, automatic retiTrn water apparatus, damper regulator, and its thermostatic control, is rendered so completely self -controlling that the attendant's care is usually reduced to supplying sufficient coal to the boiler. The system is positive in its action at all times, the air is put where it is wanted, not merely allowed to go. The pressure created within the building is sufficient to cause all leakage to be outward, preventing cold inward draughts and avoiding the possibility of drawing air from any polluting source within the building itself. Absolute control may be had over the quality and quantity of air supplied. It may be filtered and cleansed, heated or cooled, dried or moistened at will. By means of the hot and cold mixing damper, the temperature of air admitted to any given apartment may be instantly and radically changed. 65 VENTILATION AND HEATING The efficiency and economy of the system must of necessity be considered "oinder first cost and running expense, Circumstances so decidedly alter cases that an arrangement economical and easy of introduction in one building may prove very expensive in another. In most cases, however, the Sturtevant System, regarded simply as a method of heat- ing, may be installed for less money than any other system of equal efficiency. Wherever the flues can be formed in the walls and the distributing ducts are of moderate extent, the system will figure less in first cost than any other capable of attaining the same results and of supplying the same amount of air. The primary cost of a fan is less than that of any other device for moving the same amount of air. The large volume of air passing through the heater causes a condensation of steam so great that one foot of heating surface is rendered the equivalent in efficiency of three to five feet in the form of the ordinary direct radiator exposed in the room. This saving in heating surface offsets the additional cost of fan and motor. As bearing directly upon this point, Professor Woodbridge* has stated with regard to the installation in the Walker Building, of the Mass. Institute of Technology, that the saving in piping due to rapid condensation in the coils, as there arranged, was sufficient to pay for the fan, as well as an attached engine, had the latter been adopted. In all fairness, the operating expenses of any system must be compared upon a basis of similar conditions. The Sturtevant System, when taking its air from out-of-doors, cannot be properly compared with any system of direct radiation, for in the latter is lacking the advantage of the ventilation incidental to the operation of the former. But when the Sturtevant System rehandles and reheats the air within the building without outside supply, the comparison becomes more reasonable, although there will still continue to be a considerable change of air due to leakage. A six months' continuous test at the Globe Yarn Mills, Fall River, has presented data exceptionably valuable for comparison, as indicated in the accom- panying record for the period October 15, 1888, to March 15, 1889: MILL No. i. MILL No. 2. Average temperature 70 78 Coal burned for heating 31 7,000 Ibs. Coal burned for heating, ventilating and moistening . ... 286,900 Ibs. Coal burned per 1,000 cubic feet of space . 340.26 Ibs. 21 7.92 Ibs ( 100 64 Ratl { 156 * Technology Quarterly, Vol. II. No. i. 66 VENTILATION AND HEATING Mill No. 1 was heated by direct steam, with overhead pipes. Mill No. 2, which stood beside, and contained 212,663 cubic feet more than Mill No. 1, was equipped with the Sturtevant System. It is to be noted that in the mill heated by the Sturtevant System, a temperature of 78 was maintained as against 70 in the other mill, while the total amount of coal consumed for its threefold duty of heating, ventilating and moistening was only sixty-four per cent, of the cost of merely heating the other mill. The cost of janitorial service enters as an important factor in any building other than a manufactory. The Sturtevant System has been adversely criticised because of the experience required in its operation. In point of fact, it has been attempted by committees and school boards to place the control of the system in the hands of men who could sweep floors and shovel coal, but scarcely knew the difference between a boiler and an engine. It is not greater intelligence, but a different order of intelligence, that is required. When exhaust steam that would otherwise be thrown away is utilized in the heater, its cost must be considered as practically nothing. The condensa- tion in the heater of all the exhaust steam from the special fan engine reduces the cost for motive power to a minimum. As to comparisons regarding cost of repairs, much may be said pro and con ; but the character of the machinery, its few parts, slow speed of engine and fan, the sectional construction of the heater, the lack of complication of valves, the concentration of the plant at one point, and the fact that it is under the care of one man, are greatly in its favor. THE DESIGN OF HEATING AND VENTILATING SYSTEMS. It must appear from the preceding pages that the proper design of a satisfactory system of heating and ventilation is no simple matter. It is neither a question of theory nor of practice, the one independent of the other, but such a com- prehensive knowledge of the entire matter is necessary that certainty of result may be assured. As the demands for improved ventilation have increased, the problem has grown more and more complicated until it has become an evident fact that no public building of reasonable size should be trusted to other than an expert of established reputation. As a consequence, the architect looks either to an expert engineer, or to a reputable and experienced house, to develop the plans for the heating and ventilation. The B. F. Sturtevant Co. has now been directly connected with this class of work for nearly a third of a century, has fostered and established the general system of heating and ventilation by a forced circulation of warm 67 VENTILATION AND HEATING air, and stands to-day in the fore-front of those who are prepared and qualified to undertake the largest contracts wherein the fan is an essential feature. The Sturtevant System has been upheld because it is theoretically, logically and practically the best, and the sincere desire of this house has always been that the System should win upon its merits. The extensive business of to-day certainly testifies to the fact that such has been the case. The B. F. Sturtevant Co. solicits inquiry from all parties interested in improved methods of heating and ventilation ; it cheerfully furnishes complete plans and specifications for all buildings whose character would warrant the introduction of the System, and is prepared to take contracts, under its own or others' specifications, for any portion or the whole of the work of heating and ventilating where a fan is employed. 68 VENTILATION AND HEATING THE STURTEVANT HEATING AND VENTILATING APPARATUS. UPON the pages immediately following are presented, in as concise form as possible, descriptions and illustrations of the more important and charac- teristic types of apparatus manufactured by this house for the purposes of heating and ventilation. Special types and more detailed descriptions will be found in other catalogues published by this Company, and, wherever necessary, special designs will be furnished. The component parts of the Sturtevant Heating and Ventilating Apparatus are a Fan Wheel, enclosed or not as best suits the circumstances, and arranged to be driven either by belt or by direct connection .by means of some form of motor, preferably a Steam Engine or Electric Motor ; a Steam Heater, across which the air is forced or drawn ; and a Return Water Apparatus, consisting of a steam trap or of a pump and receiver arranged to operate automatically. FANS." THE FAN WHEEL. As constructed for ordinary ventilating purposes, the fan wheel consists of a series of T steel arms cast into a hub and carrying the floats or blades, which, together with the side plates of the wheel, are con- structed of light but strong steel plate, substantially as shown in Fig. 15. Here, as is the case with all wheels above the smaller sizes, two hubs are used. This construction combines the minimum of weight with the maximum of strength and durability, and is especially designed to meet the requirements of a ventilat- ing fan, namely, ability to handle the largest volumes of air, at low pressure, with the least expenditure of power. The wheel is carried by a stiff steel shaft supported in the Sturtevant patent brush oiler boxes. Constructed with the greatest care, of the best materials, and containing an oil reservoir from which the oil is continuously fed to the journal by the brushes, this box is at once unheatable , is capable of universal adjustment, and once filled with oil may be run for weeks without further attention. 69 VENTILATION AND HEATING Although this type of fan may be used without a casing where properly arranged in connection with a supply opening, it is almost universally employed wherever the wheel is to be encased, whether in sheet metal, brick or wood. Evidently a sheet metal casing may be almost as readily constructed in one form as another, so that all locations of discharge are possible, and complete steel plate housings may be readily made to conform to given and special designs. As ordinarily built, either to be driven by pulley or by direct connected engines, these various shapes of housings are illustrated on subsequent pages. FIG. 15. FAN WHEEL. DISC AND PROPELLER WHEELS. When air is to be moved against very slight resistance, as is the case where exhaust ventilation is to be accelerated, the disc or propeller form of wheel is of great service. The former is illustrated in Fig. 16, and the latter in Fig. 1 7. These wheels are light in their construction, consuming but little power at low speeds, and very easily erected. The blades of the disc fan are so set and those of the propeller wheel are so formed as to move the air forward in an axial direction. Either type is exceedingly convenient for introduction in the attic of a building, where it may be driven by a belt from an independent electric motor. An electric fan of the propeller type with direct- connected enclosed motor may be even more conveniently employed to meet the requirements. Under either arrangement, the fan is usually installed at the junction of the connections from the ventilating flues so as to present very little obstruction when not in operation. Great discretion should always be exercised in the introduction of either type of fan under plenum conditions, for it lacks the ability, except at excessive expenditure of power, to force air through a com- plicated system of distributing ducts. 70 VENTILATION AND HEATING CONE FAN. Wherever a fan wheel is to be used without casing and under conditions that require anything above the most moderate air pressure, the cone fan is particularly desirable. As ordinarily installed, it is placed close up to a division wall in which is located an inlet opening concentric with the inlet of the wheel. The air is thus drawn from one side of the wall and delivered into a space of greater or lesser extent upon the other side, where the fan is located. As ordinarily constructed and located, the type of fan is clearly shown in Fig. 18. The base of this wheel is a conoidal iron casting with its apex toward the opening in the wall, so that the air entering the wheel is gradually deflected toward the numerous curved blades which extend outward from the conoid, and are so attached to the back plate as to make a very stiff machine. A bar across the inlet, and a trussed support on the back, carry the necessary journal boxes. Such a cone fan possesses marked advantages over a disc fan in that it will deliver air against resist- ance; back-lash is impossible, and the centrifugal force of the blades is utilized. At a given peripheral speed the cone fan will give far superior re- sults in volume of air moved and in proportional power expended. Large numbers of these cone wheels have been furnished for prominent buildings r ^~^" |f - throughout the country. For certain conditions the wheel may be made double, i. e. with two inlets and conoids, and connection made to both. Or it may be enclosed in a steel plate housing in the same manner as the regular fan wheels. When a sub-basement is to be kept filled with air under slight pressure, as in the plenum system already described, this fan is very economical and convenient, as no connecting ducts are required, the fan simply standing in the sub-basement and delivering directly into it. If desired, the wheel can be fitted with a direct-connected engine placed upon the back side of the wheel ; or, if circumstances require it, the wheel may be arranged upon a vertical shaft, with step bearing, and driven by belt. FIG. 16. Disc WHEEL. 71 VENTILATION AND HEATING FIG. 17. ELECTRIC PROPELLER FAN, WITH ENCLOSED MOTOR. 72 VENTILATION AND HEATING FIG. 18. CONE WHEEL. VENTILATION AND HEATING MONOGRAM EXHAUSTER. The most substantial form of enclosed exhaust fan is shown in Fig. 19. The shell is entirely of cast iron, the support- ing hanger for the journal boxes being bolted thereto. Both bearings, which are of exceptional length and arranged for thorough oiling, are placed upon one side of the fan, leaving the inlet upon the other side entirely unobstructed for the entrance of air. It is this feature that distinguishes an exhauster from a blower, for the latter usually has a bearing upon each side and always has two inlet open- Slkk. m & s > one u P on e ^ ner s ^e, while an exhauster has that upon the side oppo- An exhauster obvi- tunity for the ready let to a system of pip- sary feature in a venti- " Monogram " fans, so- monogram cast upon larly built zontal dis- in the cut. structed to zontally at ly upward ward when Fans right or FIG. 19. " MONOGRAM only a single inlet, and site to the pulley, ously provides oppor- connection of its in- ing, a very neces- lating plant. The called from the the side, are regu- with bottom hori- charge, as shown They can be con- discharge hori- the top, direct- or directly down- occasion demands, are designated as left-hand accord- pulley, engine or ing as the motor is upon the right or left-hand side as one faces the outlet. The illustra- tion shows a right-hand bottom horizontal exhauster. The various discharges and hands of fans are indicated upon succeeding pages, showing outlines of steel plate steam fans. The capacity of the " Monogram " fans is relatively small, even in the larger sizes, when compared with the capacity of some of the large steel plate fans. The former type is, however, extremely serviceable for the ventilation of small apartments, or for forcing or drawing air through long and comparatively small conduits where the resistance to be overcome enters as an important element. Under these circumstances the particular value of this fan lies in the character of its design, tor it may be run continuously and noiselessly at the high speed necessary to produce the requisite pressure. 74 VENTILATION AND HEATINGM STEEL PLATE PULLEY FAN. For the general purposes of mechanical ventilation the steel plate cased fan is now almost universally employed. The pulley fan, as constructed in the smaller sizes, is of the form shown in Fig. 20. The sides and rim are of steel plate, built up on a cast-iron base and provided with a round outlet casting. The shaft, pulley and fan wheel are all supported by an independent " hanger " which is attached to the side of the fan, but also rigidly bolted to the floor when in position. The wheel is thus overhung on the shaft, and the inlet left free for the passage of air. In the larger sizes the construction shown in Fig. 21 is adopted. The sides are braced by angle iron, and upon each side is a supporting truss which carries a journal box. The shaft thus projects entirely though the fan, and the pulley is overhung upon one end. In the illustra- tion a blower is shown, there being an inlet upoii each side. Closing the inlet upon the pulley side would transform it into a right-handed exhauster, and render it, like Fig. 20, capable of attachment to a piping system. The standard forms of steel plate fans are well shown in the succeeding illus- trations of steam fans. It is evident, however, that any arrangement of discharge is possible, and that the material of construction makes it a comparatively simple matter to conform to any special design to suit the most exacting conditions. FlG. 20. STEEL PLATE PULLEY EXHAUSTER. WITH OVERHUNG WHEEL. 75 VENTILATION AND HEATING FIG. 21. STEEL PLATE BLOWER, WITH OVERHUNG PULLEY. 76 VENTILATION AND HEAT1NGM ELECTRIC FAN. The rapidly-increasing adoption of electricity as a motive power renders possible the introduction of the electric fan with every assurance of success. Whereas, heretofore, it has usually been necessary to provide a steam engine for the propulsion of a fan, it is now a simple matter to install a fan with either direct-connected or independent motor. For convenience and economy, the electric fan with motor directly attached presents itself as most desirable. It is thus rendered compact and portable, may be located in any position, and oc- ^zr ~~ ^ copies the minimum of space. In the smaller sizes able for the ventilation of ments a specially motor is attached di- the side of an exhaust "Monogram" type ted in Fig. 22. The becomes an integral entire machine., to be any given Where ty is re- plate fan is motor after Fig. 23. the case of fans, any matter of charge ed, the ing the fan fulfills all the requirements for heating and ventilating, and may be readily installed in connection with a heater, thus forming a steam hot blast apparatus. But the use of such a fan is necessarily largely in locations where a move- ment of air is desired at its natural temperature, that is, independent of the heating system. If the fan is to be used where steam of any reasonable pressure is employed for heating, it must be obvious that the simplest and most economi- cal arrangement would call for an engine to drive the fan, for the exhaust steam could all be utilized for heating purposes. For use in the form of an exhaust fan, as an adjunct to a plenum system FIG. 22. " MONOGRAM " ELECTRIC EXHAUSTER. is, those service- s ingle apart- constructed rectly to fan of the as indica- motor thus part of the adapted to location, greater capaci- quired, the steel fitted with a the manner of Evidently, as in all steel plate design in the shape and dis- may be follow- motor remain- same. Such a 77 VENTILATION AND HEATING of heating, the electric fan is, however, frequently of great service. It may be easily installed and operated in an out-of-the-way position as in any other, and can be arranged to be started and stopped from a switchboard in a much more convenient location, so that the attendant will seldom have to visit the fan. FIG. 23. STEEL PLATE ELECTRIC EXHAUSTER. STEAM FAN. It is always desirable that the means of propulsion for a fan should be rendered as independent as possible of any other source of power ; in other words, that the motor adopted should be devoted solely to the driving of the fan. Although the electric motor, as already pointed out, is being very 78 VENTILATION AND HEATING generally introduced, the steam engine stands as the almost universal agent for fan propulsion, the combination of fan and engine being designated a steam fan. As constructed of steel plate in the smaller sizes, the shell and wheel are identical with those used for a pulley fan. In place of the pulley and its hanger, however, there is provided a special type of centre-crank upright engine, with its cylinder above the shaft, sup- ported upon a substantial base and carrying the fan wheel over- hung upon the end of its shaft, all as illustrated in Fig. 24. In the larger sizes of full housing steam fans, the engine is of an entirely different form, as shown in Fig. 25, having its cylinder beneath the shaft, the opposite end of which is supported by a box in the inlet of the fan. Both types of engines are particularly designed for this work, are of a high grade of work- manship, and are cap- ^| ri able of sustained Up operation at high ^: : speed. Where exceptional durability or steadi- ness in running is de- sired, or where it is necessary to drive the fan above the ordinary speed, the type of steam fan shown in Fig. 26 is very efficient, the engine being double-cylindered and of the very highest grade. The running parts are entirely enclosed, thus- pro- tecting from dust and preventing the throwing of oil. Special continuous oiling arrangements are provided for all bearings. The outline cuts, Figs. 27 to 34, are self-explanatory of the standard forms in which all steel plate fans are constructed. 79 FIG. 24. STEEL PLATE STEAM FAN. VENTILATION AND HEATING FIG. 25. STEEL PLATE STEAM FAN. STANDARD TYPE. 80 VENTILATION AND HEATING FIG. 26. SPECIAL STEEL PLATE STEAM FAN, WITH DOUBLE ENCLOSED ENGINE. 81 VENTILATION AND HEATING FIG. 27. BOTTOM HORIZONTAL DISCHARGE, RIGHT HAND. FIG. 29. DOWN BLAST DISCHARGE, LEFT HAND. FIG. 28. UP BLAST DISCHARGE, RIGHT HAND. FIG. 30. TOP HORIZONTAL Dis CHARGE, LEFT HAND. FULL HOUSING STEEL PLATE STEAM FANS. 82 VENTILATION AND HEATING FIG. 31. TOP ANGULAR DOWN DISCHARGE, RIGHT HAND. FIG. 32. BOTTOM ANGULAR UP DISCHARGE, RIGHT HAND. FIG. 33. BOTTOM ANGULAR DOWN FIG. 34. TOP ANGULAR UP Dis- DISCHARGE, LEFT HAND. CHARGE, LEFT HAND. FULL HOUSING STEEL PLATE STEAM FANS. VENTILATION AND HEATING FIG. 3$. STEEL PLATE PULLEY FAN, WITH THREE-QUARTER HOUSING. 84 VENTILATION AND HEATING THREE-QUARTER HOUSING FAN. In the case of large, full housing fans, their height frequently becomes a serious obstacle to their introduction. As a means of overcoming this difficulty, fans are, therefore, constructed so that the lower portion of their scroll is formed of brick, which, with its side walls, serves at the same time as a substantial foundation. The general idea of such construction in the case of a top horizontal three-quarter housing pulley fan is presented in Fig. 35. Here the bottom part of the space within the enclosing walls of the foundation is cemented over to correspond to the curve which this portion of the fan scroll would naturally take if the entire structure were of steel plate. The three-quarter housing is of especial advantage where it is desired to connect with an underground duct through which the air is to be forced. The fan then sets directly over the end of the duct, as in Fig. 36. The duct at its end conforms to a continuance of the curve at the back of the fan. The cut shows a steam fan in which, as is customary, the engine is of the horizontal type. The long cast-iron base of this engine, attached to the substantial brick foundation, furnishes an exceptionally solid support, and renders the entire con- struction perfectly rigid. The engine proper is identical in construction with the regular independent engines of the same form, is provided with adjustment for all moving parts, is completely equipped with oiling devices, and thoroughly built for continuous operation. The utility of such a design must be evident ; in fact, this is the accepted form for introduction in the case of almost all plants of large size. The under- ground brick duct permits of the distribution of air to the vertical flues without encroaching on valuable floor space or head room. The three-quarter housing fans are constructed in the same standard forms of discharge as are the full housing fans illustrated in Figs. 27 to 34 inclusive. From this large assortment may be readily chosen the shape that is best suited to the conditions under which it must be installed. At all events, a fan of this type can be specially constructed to meet almost any conceivable requirements. The duplex type of three-quarter housing steam fan, illustrated in connec- tion with a heater upon a succeeding page, is frequently of great convenience. Each fan is provided with its individual engine, and the fans set side by side with their shafts in the same line. The shafts, which are extended until they meet, are rigidly connected by a coupling. Under ordinary conditions both engines are operated ; but, if under any circumstances, one of these becomes disabled, they may both be driven at only twenty per cent, less speed by the other engine. 85 VENTILATION AND HEATING 86 VENTILATION AND HEATING SINGLE UPRIGHT ENGINE. The most mechanical heating and ventilating plant is tor. It is, therefore, essential above all else and construction should be as near perfection The engine being the most generally employed propulsion, has received, at the hands of this most careful attention. For general indepen- well as for the driving of fans by belt, these built in a variety of forms, each best suited to The single-cylindered up- shown in Fig 3 7 is provided tling governor. The entire pie, strong and pleasing in The valve is of the bal- and receives its motion direct- trie upon the shaft. The wheel, ly heavy, is designed for a but may be utilized as a band site end of the shaft is splined ditional wheel The cylin- lagged. The from a station- oiler, and all cept that no the stationary and by dropping Although gines are constructed pressure, alsofurnish- line of sizes cylinders be operated of 40 Ibs. delicate mechanism in any usually the mo- that its design as possible, means of fan Company, the dent work, as engines are its given duty, right engine with a throt- frame is sim- outline. anced-pi-ston type iy from the eccen- which is exceeding- balance wheel, wheel. The oppo- to receive an ad- if it be necessary, der is thoroughly crank pin is oiled ary sight-feed other oil cups, ex- cross-head, are feed moving parts the oil into cups, these en- regularly for high they are ed in a full with large designed to at pressures and under, FIG. 37. SINGLE UPRIGHT ENGINE. which are usually prevalent in heating plants. A small engine of great power can thus be furnished at a comparatively low price. 87 VENTILATION AND HEATING DOUBLE UPRIGHT ENCLOSED ENGINE. Where perfection in operation, the possibility of high speed without noise, or the complete exclusion of dust from the running parts, is desired, the type of engine represented in Fig. 38 may be adopted. The cylinders are placed side by side in the same casting ; the cranks are set opposite ; the recipro- cating parts are balanced in their move- ments and high speed is made possible. The cylinders are of large diameter as compared with the stroke, so that great power may be developed at high rotative but moderate piston speed. The steam admission to both cylinders is regulated by a single piston valve, under the control of a shaft governor of the same design as that used upon the single upright engines. All moving parts sub- to friction are of steel and the bearings of ample size. Automatic re- lief valves are provided to prevent any danger of damage by water in the cylinder. Complete sight-feed oiling ar- rangements from a sin- gle oil tank connect with all of the bearings and the frame is so constructed as to en- tirely enclose all run- ning parts, while still leaving them accessible by merely opening the door. A throttling gov- ernor is usually em- ployed when the engine is used in connection FIG. 38. DOUBLE UPRIGHT ENCLOSED ENGINE. w ith a heating- plant. VENTILATION AND HEATING HORIZONTAL ENGINE. The form of centre-crank horizontal engine illustrated in Fig. 39, is of a type largely used in connection with heating-plants. It is here shown with a throttling governor, but is otherwise identical with the regular Sturtevant automatic engine of this type. The valve, which is of the balanced-piston type, is provided with snap rings and operates in a removable bushing, thereby making it a simple matter to always keep it tight. Motion is transmitted to this valve through an adjustable slide connec- tion upon the side of the frame. Continuous sight- feed oiling -JL arrangements are provided throughout. FIG. 39. Low PRESSURE HORIZONTAL ENGINE. The frame with the attached oil guard and removable side plates practically enclose the running parts of the engine, preventing the throwing of oil and largely decreasing the annoyance from dust and grit. A substantial bed plate forms a part of the complete engine. Each size high-pressure engine frame of this type is fitted with cylinders of two diameters, both having the same stroke. The smaller diameter is designed for a maximum of 150 pounds, and the larger for 100 pounds. Special sizes, with extra large cylinders and balanced slide valves, are also constructed for use at low pressure, and are thus rendered available for a special line of work for which few engines are distinctly constructed ; in fact, the Sturtevant low pressure engines stand practically alone in their class. VENTILATION AND HEATING HEATERS. CORRUGATED SECTIONAL BASE HEATER. The heater itself must be compact, efficient, easily operated or repaired, and of such construction as to make a change in its capacity a simple matter. All of these features were carefully considered in the design of the Sturtevant Heater, and the proportions in which the individual heaters are made up for use are regulated by formulas derived from the extensive experiments previously related. In Fig. 40, is indicated in detail the general construction of the indi- vidual sections of a heater. The foundation upon which the heater rests is constructed entirely of steel angles.flanged and bolted. Upon this, and the expansion balls, rests a series of sectional bases, each section containing either two or four rows of vertical pipes, according to the requirements, connected by cross pipes at the top as shown. The length of these pipes and their posi- tion prevents the evil effects of the unequal expansion of the pairs of vertical pipes, which in heat- ers of other makes, frequently have return bends in place of cross pipes. Free expan- sion lengthwise of the sections is allowed for by resting one end of the sections upon balls, E, Fig. 41, which FIG. 40. CORRUGATED SECTIONAL BASE HEATER. are supported by a casting beneath. In order to prevent alternate expansion and contraction of the air between the pipes in the heater, and at the same time economize room and material, the 90 VENTILATION AND HEATING sides of the sections are corrugated so that they fit each other closely and allow an equidistant spacing of the pipes in the heater. Upon the end of each section is a circular flanged head, divided by a horizontal diaphragm, the upper part com- municating with the steam supply, and the lower with the drip. The sides of the heads are surfaced and closely fitted ; a blank flange is placed at one end of the series and the large steam inlet and drip header at the other. These heads are tightly drawn together by substantial through bolts, and tight joints are posi- tively secured by the use of special gaskets. The upper parts of all sections thus communicate with the inlet and the lower parts with the drip. Steam is admitted through the inlet pipe A, passes into the sections, thence up, over and down the pipes, into the separate space in the see- the drip, er as water through the' Every inch of ing sur- pipes and thus util- water is tion, FIG. 41. CORRUGATED SECTIONAL BASE HEATER. which communicates with whence it leaves the heat- of condensation, drip pipe B. square the heat- face of the section is ized, and the conveyed away through the pipe in the header, in the upper part of which steam is admitted. A small hole in the horizontal diaphragm, near the middle of the section, allows of com- plete drainage of the water from each section. The pipes, C and D, are respectively the exhaust steam inlet and drip for the single independent section provided to utilize the exhaust steam from the fan engine. This section is made without a head and is not in communication with the other sections. The areas for the inlet and drip are very large and direct, giving an oppor- tunity for the use of exhaust steam without back pressure upon the engine. This arrangement does away with all inlet pipes and manifolds, with their numerous flanges and bolts ; there are no connecting nipples, allowing of con- stant racking by unequal expansion, and above all, the inlet and drip are both at the same end of the section, avoiding the great disadvantage of connecting at the opposite ends of the section. When desired, the sections may be made up in more than one group, so as to use exhaust steam in one portion and live in the other. Every heater is encased in a steel plate jacket, preventing all possi- bility of fire, and allowing of the securing of lower insurance rates. 91 VENTILATION AND HEATING STEAM TRAP. The Sturtevant steam trap is especially designed for use in connection with the Sturtevant heaters, although it is equally well fitted to remove the water of condensation from steam heaters or radiators of any con- struction. Its action will be made clear by Figs. 42 and 43. As seen in the sectional view, the body of the trap contains a pot, which, as the water flows from the inlet upon the left into the space around the pot, rises and closes the connection between the interior and exterior. The water accumulates in this space and gradually overflows into the pot until its buoyancy is overcome and it sinks to the bottom. By this accumulative action free passage for the water is afforded from the pot up through the vertical hollow extension of the cover and thence through the cored passage in the cover to the outer air. The pressure of the steam upon the surface of the water causes this discharge to be rapid, and it continues until the levity of the pot becomes sufficient to cause it to rise and prevent the passage of water by the seating of the extension against the cone screwed into the bot- tom of the pot. Both extension and cone are of brass, and are ground to a fit, ensuring a tight joint when in contact. FIG. 42. STEAM TRAP. FIG. 43. The periodic delivery of water continues as long as there is water to dis- charge or sufficient steam pressure to cause the trap to act. These traps are specially constructed to act at different steam pressures. Although certain types of steam traps are designed to return the water of condensation to the boiler, the Sturtevant trap is not intended for this service, but merely to permit of the removal of water from the heater without the escape of steam. 92 VENTILATION AND HEATING AUTOMATIC RETURN WATER APPARATUS. Economy demands that in any heating plant the water of condensation from the steam should be returned to the boiler. With a simple gravity system or with a hot blast appa- ratus placed sufficiently above the water level of the boilers, the matter of return of water is simple. But the ordinary plant for the Blower System is placed upon the floor, generally well below the level of the boilers. Some positive and additional means is therefore necessary to lift the water and force it into the boiler against the existing steam pressure. For this purpose in plants of any reasonable size a steam pump is employed. The water escaping from the heater is first discharged into a tank, which is provided tion of which when the es a certain the tank, thus set in erates until has been such a level again acts, closes t h e mission to The usu- the combi- pump and shown in Fig. 44. The latter is so placed with relation to the pump as to permit of the natural flow of water thereto. A gauge glass on the end of the receiver indicates the water level within. The pump is of the duplex pattern, always to be chosen for this class of work as it ensures more steady running and is far less liable to stoppage than a single-piston pump. When water of condensation is to be discharged into the receiver from several sources, as from direct radiators in the building and from a regular hot blast heater at the same time, it is necessary that traps be interposed, otherwise unequal condensation in different groups or coils will tend to a backing up of water in those in which the condensation is most rapid, and hence the pressure is least. With exhaust steam discharged directly into the receiver a trap is positively necessary in the connections from other coils using live steam and discharging into the same receiver. FIG. 44. AUTOMATIC RETURN WATER APPARATUS. with a float valve, by the ac- steam is admitted to the pump water reach- level within The pump motion op- tlie water reduced to that the float but this time steam ad- the pump, al form of nation of receiver is 93 VENTILATION AND HEATING VENTILATION AND HEATING HEATING AND VENTILATING APPARATUS. COMBINED CONE FAN AND HEATER. The simplest apparatus con- sists of a cone fan enclosed within the heater case, as shown in Fig. 45. By the fan's action air is forced between the pipes of the heater. The opposite end of the heater may be left open or connected by a suitable duct with any given apart- ment. For such apparatus the cone fan is far more efficient and desirable than the disc or propeller fan, because of its more positive operation against resistance. MONOGRAM EXHAUSTER AND SOLID BASE HEATER. In the smallest sizes of heating and venti- lating apparatus in which a cased fan is used in connection with a heater, the arrangement is as indicated in Fig. 46. The " Monogram " fan has already been described. The type of heater here illustrated is known as the " Solid Base Heater," and is distinguishable from the corrugated sectional base heaters used in connection with the steel plate fans by the fact that only a single casting is used for each entire heater. The steam sup ply pipe for these heaters enters the base at the bottom on one side, and the water of condensa- tion escapes from the bottom on the op- posite side. A dia- phragm in the base compels the steam to flow through all Ra ^ MONOGRAM EXHAUSTER AND SOLID the pipes, thus util- BASE HEATER. VENTILATION AND HEATING VENTILATION AND HEATING izing all the heating surface. The pipes are of steel, and the heater entirely encased in steel plate, with a receiving chamber for the air where it enters the fan. Ordinarily the air is taken in at the top, either from the room or through a pipe connecting with the desired fresh air supply. The air discharged from the fan can be conveyed to any point by means of distributing pipe. All these heaters are designed to use either live or exhaust steam. HEATING AND VENTILATING APPARATUS WITH PULLEY FAN. The ordinary installation of the Blower System requires an apparatus of larger capacity than can be conveniently constructed of the type just described. To suit all requirements, it is necessary that the construction of the heater should be such as to permit of the most extended range in its sizes, while the fan must be of a type in which the largest capacity may be secured when desired. In its simplest form, such an apparatus is presented in Fig. 47. The fan is of the steel plate pattern, driven by belt, and constructed as already described. In the larger sizes of pulley fans the "hanger" is omitted, the wheel is not overhung, and the shaft is supported by a box on each side of the shell, as in Fig. 21. The heater here consists of four independent corrugated sections of four rows of pipes each, of the type shown in Figs. 46 and 47. The air passing through the heater is, therefore, brought in contact with sixteen rows of pipe. As these pipes are set staggering, and by means of the corrugations, the sections are allowed to interlock each other, the currents of air are broken up completely and the highest efficiency secured. Obviously, more or less sections could be provided, and they could be separated by a blank flange in such a manner as to permit of using live steam in one of the groups thus formed and exhaust steam in the other. The lower pressure steam coils are always so located as to be first presented for contact with the air before it passes across the pipes of the higher pressure group, where its temperature is increased. The location of the drip is clearly shown. When live steam is used this is connected with a steam trap provided for the purpose, in order to free the heater of water without allowing any escape of steam. Arranged as here shown, this is known as a " draw-through apparatus," the air first passing through the heater before it enters the fan. The direction of discharge of heated air from the apparatus is, therefore, entirely dependent upon the construction of the fan. Although here shown with a bottom horizontal discharge, it is evident, from preceding descriptions, that fans of this type are regularly made in a large variety of directions of discharge, so that change in direction of the air after once leaving the fan is usually avoided. 97 VENTILATION AND HEATING STANDARD HEATING AND VENTILATING APPARATUS. As has already been indicated, a steam engine is an almost indispensable requisite to any steam hot blast apparatus of more than moderate size. For compactness nothing can excel the combination of corttigated sectional base heater and steel plate steam fan. In the smallest apparatus, of which the steam fan forms a part, the latter is of the type already illustrated, with ver- FIG. 48. STANDARD HEATING AND VENTILATING APPARATUS. SMALL SIZE. tical engine, having its cylinder above the shaft, and one bearing upon either side of the crank, leaving the fan inlet unobstructed, as shown in Fig. 48. The heater is constructed on three sections, each having four rows of pipe, all connecting with the same inlet header, and one section of two rows (not seen in cut) provided to utilize the exhaust steam from the fan engine. Either live or exhaust steam may be used in the heater. Heaters of this size are usually set up on a timber frame, so as to allow of placing the trap upon the floor and connecting the drip directly to it. 98 VENTILATION AND HEATING 99 VENTILATION AND HEATING In the larger sizes the apparatus maintains its general form, the principal change being in the construction of the steam fan, which, as indicated in Fig. 49, has the engine cylinder beneath the shaft. BLOW-THROUGH HEATING AND VENTILATING APPARATUS. In the introduction and erection of the Sturtevant steam hot blast apparatus, it frequently happens that the space allotted is of such a shape as to preclude all possibility of placing an apparatus of the ordinary form, arranged to draw the air through the heater before it passes through the fan. If the space is narrow, but of considerable length, it is often a very simple matter to construct the fan to blow the air through the heater, as illustrated in Fig. 50. This makes a narrow, but long, apparatus of equal efficiency with the regular standard apparatus. Such an arrangement is frequently desirable where a pulley fan is to be used in place of a steam fan, and it would be impossible to belt directly to a fan arranged in the regular manner. The outlet from the heater may be placed in almost any position at the end of the heater, so as to discharge either directly outward at the end, or upward, downward, to the right, or to the left. The discharge of the fan is always made such as to cause the most thorough circulation of the air passing through the heater, that is, with the discharge at the top of the heater the fan would have a bottom horizontal discharge, while with a bottom discharge on the heater the fan would be top horizontal, as shown in the cut. The heater shown in the cut consists of four sections, each having four rows of pipes, and all being bolted together in a single group connecting with the same inlet header and drip. Either live or exhaust steam may be used in this portion of the heater ; in the former case, the water of condensation is discharged through a steam trap, while in the latter it has a free delivery to the open air, or connects with a return system. In addition to these sections is one more, to utilize the exhaust steam from the fan engine. This section, having no circular head and not projecting through the heater casing, cannot be seen. The section into which is discharged the fan engine exhaust is always so placed in the heater as to be the first with which the cold air comes in contact, because exhaust steam, having a lower temperature than live steam, would have but little effect in heating air which had already passed through the live steam coil. It is customary in heating and ventilating plants employed in manufactur- ing establishments to use in the main group the exhaust from the mill or shop engine during the day, and live steam during the night. 100 VENTILATION AND HEATING c/> K ft. IX . S3 S < o Q- 2 p , t/J lowest class of society during a sensational trial, is by extraordinary pollution of the atmosphere, germs are rampant and their effect can only most bountiful supply of pure, fresh air. devoted to the combined requirements and a State library is presented in Figs, court room, the wall of which is shown certain to be accompanied Vile odors and disease be overcome by the A building of a court house 91 and 92. The broken away in the height of two ters, in flues Fig. 91 , extends up for stories. Two regis- located in the inner wall, force the FIG. 91. N, H. STATE LIBRARY AND COURT HOUSE, CONCORD, N. H. air toward the opposite and outer wall, whence, following the downward course, due to its being cooled, it returns toward the inner wall and escapes through fireplaces and adjacent registers in the side walls. A separate floor register is also provided for supplying the judge's bench, which is upon the outer side of the room. The adjoining smaller rooms, devoted to uses of the court and jury, are treated as are similar apartments in other buildings, with supply from overhead registers in the inner walls and ventilating registers at floor level and in the same walls when possible. The library portion of this building, as will be seen by Fig. 92, consists of a main stack room with alcoves. In each of the partition walls between alcoves 154 VENTILATION AND HEATING are located vertical flues from which hot air is delivered to each alcove, thereby keeping their most exposed portions warm. Thence it passes to the main room with its less exposure, whence it escapes through ventilating registers, as indicated. The great value of the books of a library necessarily demands the utmost care in the introduction of the heating system to the end that they may not be injured FIG. 92. N. H. STATE LIB. AND C. H., CONCORD, N. H., FIRST FLOOR PLAN. by overheating. In this case the air is admitted above the tops of the book stacks in such a manner as to prevent its immediate contact with any of the volumes. The apparatus, located in the basement, near the centre of the building, is so arranged that cold air may be conducted to the bases of the flues to the court room, where, in combination with the hot air from separate ducts, it may be admitted to the court room, but constantly under the regulating power of thermostats, which thereby maintain a constant temperature within the apart- ment without affecting the volume of air admitted. 155 156 VENTILATION AND HEATING CHURCHES. The treatment of a church depends largely upon its design. If the floor is arranged upon the amphitheatre plan, the air may be admitted much as in the case of a theatre. But the usual construction presents a floor that is practically level and compels the introduction of air vertically through it, or else its supply from the side walls. To secure the best distribution the latter arrangement is usually adopted, rendering the manner of heating the ordinary church but little different from that of a hall of audience. The intermittent use of a church, however, introduces one of the most important problems in the design and introduction of a heating and ventilating system. As a rule, upon Sunday, practically all the rooms in the building are in use, sometimes the auditorium and Sunday-school rooms coincidently, some- times consecutively, while less frequently one is occupied in the morning and the other in the afternoon. Furthermore, the parlors, pastor's study, or small lecture rooms, may be required to be warmed only on certain days of the week. Evidently, then, the system installed must be varied in its adaptability and rapid in its ability to warm up the building after it has been thoroughly cooled down. For the occasional warming of small rooms where ventilation is not an all-essential feature, direct radiation will be found most advantageous, while provision may also be made for supplying air to the same apartments when the apparatus is in operation. FIRST BAPTIST CHURCH, MALDEN, MASS. In the structure illus- trated in part in Fig. 93, the auditorium and Sunday-school are located upon the same floor, the latter being flanked upon two sides by two tiers of class- rooms and parlors, arranged to be separated from, or form a part of, the main room at will. The apparatus is located in the basement, near the centre of the structure, and pipes extend therefrom to the various vertical flues, the location of a sufficient number of which is indicated to make the arrangement clear. Each flue in the side walls of the auditorium is provided with two registers, the lower at floor level, to be employed when first warming up. Ventilation takes place through wall registers set near the floor, whence the foul air passes to the roof space and out of a roof ventilator. The main Sunday-school room is supplied and ventilated as indicated by the location of the registers, while the classrooms and parlors are individually heated and ventilated. Direct steam radiators additionally heat certain of the apartments. The social hall in the basement is supplied directly from the fan. 157 LU g ul VENTILATION AND HEATING THEATRES. Theatres, of all halls of audience, require the greatest care and the most extended experience in the designing of a system of ventilation and heating adequate for their requirements. They consist of three different parts: the entire body of the house or auditorium ; the stage and dressing rooms ; and the foyer, lobbies, corridors, stairways and offices. But the distinction and separa- tion between these different parts changes at different times during a perform- ance. The simple rising of the curtain throws into one the two previously distinct apartments the auditorium and the stage. So too, when all the doors or portieres are opened into-the corridors, the distinction between the auditorium and corridors is materially lessened. It will be readily seen that arrangements based entirely upon the constant separation of these various apartments may be seriously affected, if it is possible to so suddenly and radically change these conditions. As a rule, theatres are located in cities with buildings abutting on two or more sides and allowing of no direct connection, by windows, with the external air. In fact, none but artificial means can ever produce satisfactory results in such places, and, furthermore, only a system of forced circulation has com- plete control over all conditions. Generally speaking, it is advisable to create a slight excess of pressure in the auditorium, in order that all openings shall allow for the discharge, rather than for the ingress of air. This condition will cause the curtain to swell slightly toward the stage, and will ensure the leakage of air from the auditorium to the corridors rather than the reverse, which under certain conditions may be decidedly objectionable. The general methods of air intro- duction and distribution in such a building have already been pointed out. The close seating of the occupants produces a large amount of animal heat, generally increasing the temperature five or six degrees and, quite frequently, fully ten degrees, evidently so much that, considering a theatre once filled and thoroughly warmed, it usually becomes not so much a question of warming as of cooling to produce comfort. Occupied us such buildings are for a number of hours, a continuous working system must be provided, and no reliance placed on one that puts the atmosphere in good condition at the beginning of a performance, but fails to maintain that good condition to the end. Architects have during late years devoted a great deal of attention to this matter, with marked improvement in the condition of newly-constructed theatres. Many failures have, however, resulted from inexperience, and a lack of realization of extraordinary requirements in such structures. 159 VENTILATION AND HEATING CASTLE SQUARE THEATRE, BOSTON, MASS. Evidently there is great opportunity for variety in the heating and ventilating arrangements that may be introduced in a theatre. While side wall flues and openings may to a FIG. 95. CASTLE SQUARE THEATRE, BOSTON, MASS., BASEMENT PLAN. certain extent fulfil the requirements, they are, nevertheless, so located that the air discharged therefrom can never do its most effective work in the way of ventilation. Although the system of ceiling supply by means of a plenum fan 160 VENTILATION AND HEATING discharging through a perforated ceiling, with a resulting downward movement of the air enforced by an exhaust fan drawing from floor openings, possesses many advantages, and has to a considerable extent been introduced, yet it has seemed advisable to illustrate here the more common method of floor supply and upward air movement. In this theatre, clearly presented in its general arrangements in Figs. 94 and 95, there is practically no external exposure, only a little more than the width of the doors upon either side. The front is faced with a hotel, as is also the rear of the stage. Therefore, the entire theatre is, to all practical purposes, entirely enclosed. The skeleton structure is of steel beam and girder work, while all arches, partitions and similar portions are of tile or terra-cotta, making an ideally fire- proof structure. Immediately surrounding the orchestra circle is the usual partition separating it from the foyer and lobbies. Above the level of the first floor this partition is formed of a double wall of terra-cotta, with space between. The space in the basement between this partition and the outer wall of the theatre forms a passage -or conduit some ten feet in height. Located in this passage, at a point convenient to the fresh air supply from above the roof, is a special cone fan of the general type illustrated in Fig. 18, set to the extent of about half its diameter into a properly-shaped pit. Adjacent thereto is the heater enclosed in a brick chamber, while an engine furnishes the motive power to drive the fan by belt. The air (heated or otherwise, as may be nec- essary), as it leaves the fan, passes in properly-proportioned volumes in either direction along the passage, whence the greater part is allowed to escape to the space beneath the auditorium proper. In smaller volumes it is delivered to the first and second balconies through flues in the pilasters and through the hollow walls at the rear of the auditorium. Through the large flues, near the boxes, and upon either side of the auditorium, air passes to large wall registers, as shown in the section, and also to the space beneath the second balcony floor. The boxes are supplied through special flues, which discharge into the passages with which they connect, whence the air enters the boxes beneath the doors, which are cut short, and passes across the occupants to the body of the house. The principal supply for the auditorium amounting to nearly 30,000 cubic feet per minute for the orchestra and orchestra circle alone, and as much more for the balconies, is admitted through the floors of these respective por- tions. In the case of the main floor, the space beneath it permits of the ready distribution of the air admitted thereto through the numerous openings in the basement partition wall. 161 VENTILATION AND HEATING The chair legs throughout the entire house are provided with special latticed castings, as shown in Fig. 96, forming thereby a large number of air chambers to which air is discharged through openings in the floor immediately beneath them. The air thus passing through the floor openings at relatively high velocity is permitted to escape beneath the persons of the occupants with low and imperceptible movement, and then pass upward to the ceiling vents. These vents, consisting of a central ceiling opening of moderate size and numerous smaller openings in the ceiling at the back of the second balcony, provide for a backward sweeping movement of the air across both first and second balconies, thereby securing the highest efficiency from a given volume of air. Special ventilation from the orchestra circle and the extreme rear of the first balcony is also indi- cated in the sectional view. From the roof space to which all this foul air passes, it is exhausted by a large electrically driven cone fan, located upon the roof above the stage and discharging freely into the atmosphere. All escape of odors from the toilet and smoking rooms to other apartments is avoided by providing special and positive exhaust venti- lation therefrom by means of an exhaust fan, located in the basement, which connects with a series of vertical flues. The same fan also serves to remove the heated air and odors from the kitchen and the boiler and dynamo rooms beneath the hotel. The foyer is supplied with warm air through registers in the walls beneath the stairs, and is independently ventilated through its triple-domed ceiling. The stage is heated by means of steam coils at the back suspended just beneath the floor, cast-iron gratings being provided through which the heated air may pass upward. The temperature throughout the auditorium is regulated by a thermostat arranged to operate a by-pass damper on the heater, so that any desired tem- perature of the air passing to the conduit may be secured. To avoid trouble from too great and sudden cooling of the air, a minimum thermostat is also introduced, which, as usually set, prevents the admission of air to the auditorium at a temperature lower than 65. With this arrangement this temperature is readily and uniformly maintained at 70 throughout the house, while 30 cubic feet and over is supplied per minute to each occupant. FIG. 96. 162 W VENTILATION AND HEATING DWELLINGS AND OTHER BUILDINGS. While characteristic types have been chosen for illustration in the pre- ceding pages, it must be evident that it is impossible in this comparatively small compass to completely cover the wide range of variety in the construction and uses of buildings. The dwelling house, for instance, has not been pre- sented, but it by no means follows that its ventilation and heating may not be easily accomplished. Simply because of the similarity of treatment of an office building and a dwelling the latter has not been illustrated. While the Sturtevant System meets the requirements of domestic heating and ventilation, nevertheless, because of its mechanical nature it is more or less unsuitable for introduction in a moderate-sized dwelling. But in the large private residence or in the apartment house, where careful attendance is assured, it evidently surpasses any other method. Objectionable furnace gas is avoided, danger from leaking direct-steam or hot-water radiators cannot occur, and the supply of air is no longer at the mercy of the atmospheric changes. In its most perfect form the hot and cold arrangement of the system should, of course, be installed ; but the single-pipe system will, under ordinary conditions, meet the requirements of good ventilation, for the air supply by the Sturtevant System is usually far in excess of the requirements. The perfec- tion of the electric motor and the extension of power circuits is simplifying the introduction of the system in dwellings, for under such conditions of power supply low-pressure steam may be employed for the heating and the speed of the motor, and consequently the movement of the fan readily regulated. For either the permanent or temporary heating of large, open structures like exhibition buildings this system is particularly adapted. It secures uni- formity in the warming, and by means of an apparatus that is readily portable. The Horticultural Building, at the World's Columbian Exhibition, was thus treated, apparatus of large capacity being placed within the huge floral mound which stood just beneath the dome. From the highest point of this mound the warm air was discharged, volcano-like, toward the glass-roofed dome, whence by its cooling action it gradually setttled to the floor and was thence drawn back once more to the apparatus. Evidently, after the Fair, the various apparatus, unlike a lot of direct-steam piping, were still in marketable form. The Sturtevant System has been extensively employed for the double pur- poses of heating dye nouses, paper mills, and the like, where great quantities of steam are produced, and of clearing the interior atmosphere by absorbing this steam by means of the large volumes of heated air. 163 VENTILATION AND HEATING 1 -3 V l<< M *\ 1 FIG. 97. STEAMSHIPS " ST. PAUL " AND " ST. Louis." 164 VENTILATION AND HEATING STEAMSHIPS. While efforts are continually being made by all the great steamship com- panies, notably those that compete for the travel between Europe and America, to improve their ships, reduce their time of passage, and to make comfortable the passengers, no expense being spared in decorations and luxurious fittings of the saloons and rooms which are the temporary home of travellers, it is a pleasure to be able to record the fact that the matter of ventilation is now receiving its share of attention. There is no doubt that one of the greatest defects in a modern steamship has been the failure to provide an adequate and constant supply of pure air at all times and in all parts of the ship that are occupied by passengers and crew. Much of the discomfort of an ocean voyage, including seasickness, arises from the bad air which every one is obliged to breathe when below decks with the air ports closed, especially in rough weather. The remedy is simple, effectual and inexpensive. By means of a fan the state- rooms and saloons can be given the freshness of the outer air, instead of the stuffy and oppressive atmosphere that now characterizes them. The problem is of equal importance in naval vessels, and the course of its inception and successful solution in the American Navy has had a great influence in leading the merchant marine to adopt this most beneficent improvement. In March, 1878, the Secretary of the Navy appointed a board of officers " to examine and ascertain the best system of ventilation, by mechanical means or otherwise, by which the ships of the Navy may be more perfectly ventilated than at the present time." This board made an examination of the U. S. S. " Richmond," and reported : First, upon the necessity of ventilation, showing. " the filthy condition of the atmosphere generally on shipboard, which both men and officers are compelled to breathe; thus inducing disease, impairing health and increasing the mortality." Second, upon the necessity of some mechanical device to keep up the circulation of air, giving reasons why " no system of ventilation can be relied upon which depends for action on induced currents produced by the difference of densities or the difference in the static and dynamic heads of the internal and external air." As a mechanical device for ventilating, it was recommended " that a fan of the most improved type, and one that has been thoroughly tested and found efficient, be adopted." Two fans, the first constructed for this purpose, were built by B. F. Sturte- vant. After twenty -five days at sea, Chief Engineer Baker wrote : " It may be confidently stated, that the ' Richmond ' is now by far the most completely venti- lated ship that ever sailed under the American flag, or, indeed, under any flag." 165 VENTILATION AND HEATING STEAMSHIPS "ST. PAUL" AND "ST. LOUIS." These magnificent new twin transatlantic liners of the International Navigation Co. undoubtedly stand to-day as the most perfectly heated and ventilated vessels afloat. All other means of heating were discarded, and the Sturtevant System adopted throughout. The system is duplex in its operation, one series of fans, with their attached heaters, serving to furnish pure warm air to practically all occupied portions of the ships, while a separate set of exhausting fans is arranged to withdraw the air, and to thereby compel its complete circulation. The presence of water-tight bulkheads naturally prevented the horizontal extension of air pipes throughout the lower decks. Four separate plants were therefore introduced, each plant consisting of a heating and an exhausting apparatus, both located on the shade deck, and driven by direct-con- nected electric motors. From each of these apparatus pipes extend downward, and upon each deck connect with horizontal systems ; no pipes passing through the transverse bulk- heads. The general scheme of this arrange- ment is indicated in Fig. 97, showing, in outline, a longitudinal STATEROOM. section and plan of the shade deck which embraces one of these systems. Smaller auxiliary fans, one shown on either side of the ship, supply fresh, cool air direct to the engine rooms, while the large fan, presented in side elevation, is devoted solely to exhausting from the galley. All pipes are carried close up to the deck or deck beams above. On the berth deck the supply ducts are extended down each of the stateroom alcoves, discharging the air overhead toward the side of the ship, as indicated in Fig. 98. Positive circulation throughout the stateroom is accomplished by extending an exhaust pipe down behind the commode and dressing case, as shown, and pro- viding it at the bottom with a suitable opening. The latticed panel permits of ready passage of air when the door is closed. 166 VENTILATION AND HEATING TESTING SYSTEMS OF VENTILATION AND HEATING. The actual efficiency of any system of ventilation and heating cannot be ascertained by mere casual inspection, but only by careful, intelligent and exten- sive experiment. Trustworthy results can only be obtained by the use of special instruments designed for such investigations. Among the most important for this purpose are those here presented. Good thermometers, of the usual construction, are generally sufficiently accurate for observing the ordinary temperature of air, but for noting the temperature of steam, or of highly- heated air, the form shown in Fig. 99 is very convenient. The thermometer tube is enclosed in a tubular brass case, the lower end of which is provided with a screw of standard size and thread, by means of which it may be securely in- FlG loa ANEMOMETER serted in any T or flange. The tube pro- jects well down below the threaded portion, and is guarded by a small pipe attached to the bottom of the case, which allows free circulation around the bulb of the thermometer. The glass may be graduated to read between any given temperatures. For instance, if the ther- mometer is to be employed exclusively for ascertaining the ordinary temperature of steam, its range need not be greater than between the points 200 to 3 50. Under ordinary conditions the volume of air flowing through a given passage or orifice may be most readily determined by means of an anemometer. This instrument, of the form illustrated in Fig. 100, consists of a light and delicately constructed fan wheel whose motion is transmitted to a practically frictionless system of gearing within the attached case. The movement of this system of gearing is rendered evident by the hands and graduated circles upon the dial. The velocity of the air, in FlG. 99. HIGH-GRADE ^ ee * P er minute, is indicated thereon, the series indicating 'THERMOMETER. 10 , 1 > 000 > 10,000, 100,000, 1,000,000 and 10,000,000 167 VENTILATION AND HEATING respectively. Evidently the velocity thus obtained, corrected for any known error of the instrument, multiplied by the area of the passage, must give the total volume of air passing. Air pressures may be determined by means of the ordinary U tube, one end being connected with the given space or passage and the other with the atmos- phere, the difference in pressure being indicated by the difference in level of the water in the two legs of the tube. This reading of pressure differences in inches of water may be readily trans- formed into pressure in ounces by multi- plying by .578 this factor being the equivalent, in ounces, of the pressure due to a head of one inch of water. The humidity of the air may be ascertained by a hygrometer, shown in its most convenient form in Fig. 101. It is provided with two standard ther- mometers, one the dry bulb show- ing the temperature of the air, the other the wet bulb the temperature due to evaporation. When the air is satur- ated no evaporation takes place, and the two thermometers indicate the same. Between the thermometers, and enclosed in the case behind the slot, is a cylinder arranged to be freely turned by the knob at the top, and upon which is inscribed a series of columns of figures numbered at their headings. The instrument here shown was spe- cially designed for high temperatures, and a double set of columns is given. These numbers represent the difference FIG. 101. HYGROMETER. in temperature shown by the two trier- 168 VENTILATION AND HEATING mometers. The vertical columns beneath them exhibit the relative humidity, which may be read off beneath the figures at top of column, indicating the difference of temperatures and opposite to the temperature of the wet bulb, as shown on the scale at the left of the cylinder. The amount of carbonic acid present in the atmosphere may be readily ascertained to a sufficiently close degree for practical purposes in the following manner. Six clean, dry and well-stoppered bottles, containing respectively 100, 200, 250, 300, 350 and 400 cubic centimeters, a glass tube containing exactly 1 5 cubic centimeters to a given mark, and a bottle of perfectly clear, fresh lime- water, constitute the apparatus required. The bottles should be filled by means of a hand -ball syringe with the atmosphere to be examined. Add to the smallest bottle 15 cubic centimeters of the lime-water, put in the cork and shake well. If turbidity appears, the amount of carbonic acid will be at least 16 parts in 10,000. If no turbidity appears, treat the bottle of 200 cubic centi- meters in the same manner; turbidity in this would indicate 12 parts in 10,000. In similar manner, turbidity in the 250 cubic centimeter bottle indicates at least 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 only be attained by special study and a knowledge of chemical properties and methods of investigation. 169 UNIVERSITY OF CALIFORNIA LIBRARY Los Angeles This book is DUE on the last date stamped below. ,.78 FormL9-25m-8,'46(9852)444 T ot A i Til 7655 Sturtevant. B.F., S93v oo . , Boston, Lfess. 1906 Ventilation and heating. TH 7653 S93v 1906