NE of the many problems of growing seriousness confronting the designing and the operating engineer is that of waste prevention. Among the larger and more preventable of modern wastes in things material is that of fuel, a waste that begins in the mining, attends the transportation, and ends in the using of coal for both power and heating purposes. The world's daily consumption of fuel approximates an equivalent of 5,000,000 long tons of coal, which may be roughly represented by a continuous train of fully loaded cars one thousand miles in length. It is but necessary to so visualize such a daily draft upon the world's supply to impress upon the imagination the rate at which it is being consumed, and at which one of the world's great sources of available energy is approaching exhaustion.

One purpose of this paper is to present a method successfully employed for reducing the waste of heat, and therefore of fuel, in the warming of buildings. For the reason that properlydesigned heating systems are intended to provide a rate of thermal output equal to the maximum rate of heat losses from the buildings to which they are adapted, the opportunity for waste in weather milder than the coldest is abundant. The remedy lies in providing a reliable and surely controllable thermal output by installed heating systems which shall be equal to, and which shall not exceed, the normal rates of heat loss by the buildings served.

METHODS OF CONTROLLING WARM AIR AND WATER HEATING SYSTEMS.

Some methods of heating afford simpler and better means for controlling thermal output than do others. Generally speaking, they are those in which control through manipulation is reduced to a minimum, in which the human factor is as far as possible eliminated. The heat yield from a warm-air furnace system may be, and commonly is, controlled at one point, the furnace, by the intensity of draft used, and by the service of a single attendant. So also in the case of a water

heating plant, the control may be wholly at the boiler, by a regulation of the temperature of the circulating water in close accordance with the fluctuation of the weather temperature, the cloudiness, the force of wind-all factors in affecting the rate of heat loss by buildings.

In that feature of water heating, the ability to control at one point the thermal output of the entire system to exactly match the heat loss by the building to which it is correctly adapted, and also in the lower temperature of the water "boiler" than that of a steam boiler doing the same work, lies the higher economic operating value of water heating than that usual, or generally possible, in steam heating. In the case of water heating systems the control may be, and most frequently is, at one point, the boiler room, and by one operator, the fireman. A greater economy in the use of fuel for heating purposes is hardly possible than that attainable in the use of a water heating system successfully designed, installed and operated.

POSSIBILITIES IN CONTROLLING STEAM HEATING SYSTEMS.

In the case of steam systems, the thermal output from radiators and convectors is commonly controlled by valves locally operated. In rooms large or exposed enough to require more than one radiator, the thermal output may be regulated by the number and the surface of the radiators steam filled. If three radiators in one room have relative surfaces 1, 2, 4, it becomes possible, by means of such division of surfaces and the several combinations they afford, to produce relative thermal outputs 1, 2, 3, 4, 5, 6, 7. Where the heating is done by pipe surface ranged along the walls of an enclosure, that surface may be so connected into valved manifolds as to effect the same surface combination and range of thermal output. Such equipments, however mechanically ideal they may be, are practically unreliable because of the too general failure of the human factor to which the regulation must be entrusted.

SUBDIVISION OF HEATERS FOR WARMING TEMPERED AIR.

In the author's experience such subdivision of heaters has been found to be far more successful in the case of convectors for warming air for ventilating work than in the case of radiators for heating service because of the far less number of valves to be manipulated. Thus in a convector designed to raise 72,000 cu. ft. of air per minute from 0° to 70° F., 980 pipes, 15 ft. in length, including expansion pieces, may be arranged in the following manner :

The steam and condensation headers are made up in the manner shown in Fig. 1. These headers are each made for fourteen pipes connections, and five headers are grouped into one manifold for steam, and into another for condensation, and each sub-group of fourteen pipes is connected for removal and repair, and each group of 70 pipes is valved for cutting out for that purpose, but not for temperature control. This arrangement provides a wall of 140 pipes one pipe deep under the control of valve No. 1; another wall of 280 pipes, two pipes deep under the control of valve No. 2; and a third wall of 560 pipes four pipes deep under the control of valve No. 3. For an outside temperature of 60° and to raise the air passed through the heater to 70° F., valve No. 1 is opened; for outside 50°, valve No. 2; for outside 40°, valves Nos. 1 and 2; for 30°, valve No. 3; for 20°, valves Nos. 3 and 1; for 10°, valves Nos. 3 and 2; for 0°, valves Nos. 1, 2 and 3. This arrangement, combined with changes in steam pressure to fill in the interval requirements between the 10° stages, has been found to give a well-nigh complete control of the temperature of air passed through the heater at a fixed and predetermined rate of flow.

In some forms of convectors the same effect may be produced by mixing dampers, either automatically or manuallyoperated.

within rooms under normal conditions of heat loss, the opening of windows or doors would quickly result in such chilling as to insure an early closing of those abnormal avenues of heat escape.

ADVANTAGES OF THE FIXED ORIFICE.

A very simple and effective method of temperature control, which involves a minimum of manipulation and of dependence on that most unreliable of operating agents, the human factor, and which reduces to as low a degree as can any method the impulse to open windows, and which automatically compels the closing of all abnormal ways of heat loss, is that which employs the fixed orifice and the variable pressure for the supply of steam to heaters. The "modulating" valve method of temperature control, as that method is generally applied and employed, may be generically described as a variable orifice with fixed steam pressures. Mechanically, that method is complete, and all sufficient. Practically, it is defective, because dependent on as many human factors as there are valves to be manipulated. The too common result is that the valves are not used to "modulate," or to vary the steam-way aperture, but as opening and stopping valves, being thrown to wide open or to tight closed. In the large majority of cases examined the exceptions to that procedure have been relatively few.

EFFECT OF OPENING WINDOWS.

If

So also in the case of direct heating by radiators, the human factor may be practically eliminated by the employment of reliable thermostatic means for temperature control, and generally to the decided economic advantage of the operating of the systems in which they are incorporated. The large initial costs of such installation, and, with some makes, the maintenance charges, are make-weights against the general employment of this method. However perfect in design, workmanship and action, thermostatic control is in one important respect inherently defective as a contributor to economy. the windows of a room or a building are thrown open, or the location in which a thermostat is placed is cooled by currents of admitted outside air, the radiator or the convector valves will remain open, and a full supply of steam will be fed to the heaters as long as the condition described is maintained. It is supposedly a function of the thermostat to prevent that rise of temperature within enclosures which tends to relief by opening windows, but, once the windows are opened, the thermostat does its utmost to prevent a temperature condition within the room affected which would tend to a closing of windows.

The monotony of an unchanging evenness in air, even of the purest quality, in a static temperature, though supposedly ideal, becomes in time, oppressive and gives a sense of stagnancy, simply because of the physical and normal demand for stimulating variety. As surely as it is true that prolonged static conditions within a room induce demands for relief through visible connection with outside air, windows are likely to be thrown open unless held fast by rigid rules or binding nails.

Whatever among the methods of temperature control thus far described may be used, there is nothing in their functioning which compels the closing of windows or doors because of discomfort attending such opening. If, on the other hand, the heat yield from radiators or convectors be made only that required for maintaining any desired temperature

STEAM MANIFOLD

DETAIL A

CONDENSATION MANIFOLD

FIG. 1-ARRANGEMENT OF STEAM AND CONDENSATION HEADERS WITH DETAIL OF FIXED ORIFICE.

The reverse method, that of fixed orifice and variable pressure, has certain and considerable advantages over that of variable orifice and fixed pressure. Let a system comprising ten, or a hundred, or a thousand radiators be so planned that each radiator when steam-filled at atmospheric pressure shall yield a thermal quantity equal to the full part it is designed to play in the severest of weather. Let the maximum pressure to be carried in the steam conveying and distributing ping be fixed at any point desired. Let the steam pass into cach and every radiator through an orifice of such area that, when the steam in the piping is at the fixed maximum pressure, the quantity of flow will just steam-fill the radiator when

ditions of outside weather would be approximately as shown in Fig. 2.

A steam heating plant so designed and operated has in all respects thus far noted the simplicity and thermal flexibility of a water heating plant, and, with one exception, the operating economy of such a plant. At the boiler end of heating systems hot water has the advantage over steam because of the larger proportion of heat extracted from the combustion gases by the cooler fire surfaces of the water "boiler." Allowing 18 lbs. of air per pound of coal, and 300° F. rise of temperature in chimney gases above the air of the boiler room, one-tenth of the heat produced by a perfect combustion of the best of coals is passed to the chimney. Roughly, then, each 100° increase in that temperature rise adds between 3% and 4% to the loss through the chimney. The yearly average excess of temperatures of chimney gases escaping from a steam boiler running under 5 lbs. steam pressure above that of gases escaping from a water boiler with temperatures averaging 150° is 87°, representing a safely estimated excess loss of more than 3% chargeable to low-pressure steam heating.

OTHER FEATURES OF FIXED-ORIFICE METHOD.

A further economic advantage attaching to the fixed orifice method of supplying steam to heaters is in the possible elimination of all valve appliances for the feeding of steam to, and for the removal of air and of condensation from, such heaters. Both air and condensate may be passed by gravity through open and valveless pipe ways to the boiler room, the air there venting upward and the water flowing downward and enter

or other mechanism adapted to conditions peculiar to each case. It is important that steam be kept from passing into return piping in sufficient quantity to pass into heaters through their open return connections, and to prevent such occurrence the surface of radiators and convectors may be increased for the purpose of condensing any surplus of steam supplied to them through any slight defect of orifice or pressure adjust

ment.

The method described commends itself because of its simplicity of design, economy of installation, flexibility of performance, reduction of waste through over heating, prevention of waste by any protracted openness of windows, and the elimination of that multiple factor of hand manipulation of many and scattered radiator or convector valves.

TYPICAL APPLICATION OF FIXED ORIFICE SYSTEM.

The first knowledge by the writer of a system of the kind under consideration was in a group of church buildings costing approximately $180,000 and intended to be as complete as modern art and science could furnish. The building committee, dissatisfied with all the many church heating systems examined, because of ill adaptation of means to producing results sought, and the consequent irregularity and inappropriateness of heating effects, proposed a dual system of water for mild and moderately cold weather, and of steam for use in severe weather. The employed engineer discouraged such complications and expense, as wholly unnecessary, and for a church auditorium seating 750, a Sunday School room seating 250, and entertainment room accommodating 175, a parish house containing two minor auditoriums ten class rooms and large culinary quarters beside rooms for choir, lockers, coat and toilet uses, he designed a complete steam system of the fixed orifice and variable steam pressure type, including a generous ventilating system for all five assembly rooms, all installed complete under a contract cost of less than 5% of the total cost of the church establishment. The auditorium is heated by eighteen concealed heaters of 185 sq. ft. each, to each of which steam is supplied through a bored bushing placed in the steam pipe connection with the radiator, and all are furnished with steam through piping under pressure, controlled by a single and easily accessible valve, the pressure carried being made to vary with weather conditions. The entire equipment in its several divisions is similarly arranged and operated.

PRINCIPLE USED IN DESIGN OF SYSTEMS FOR WASHINGTON CATHEDRAL.

The system planned for the National Cathedral, Washington, D. C., and described in THE HEATING AND VENTILATING MAGAZINE for April and May, 1920, by Charles L. Hubbard, is designed on the same principle. The proposed equipment is to consist of eighty-six convectors rated at more than 360 sq. ft. each, each supplied by steam through a fixed orifice, and through steam mains and branch lines aggregating a quarter mile in length, and the whole under the control of a single regulating valve by which the pressure of steam in the four mains and their runouts is under ready and reliable adjustment and holding. The arrangement insures an even and simultaneous distribution of heat throughout the great edifice, approximately 500 ft. in length, and in proportions desired for each of the five principal sections of nave, transepts, tower, choir and sanctuary, and for the four cardinal exposures. Were the heaters valved for steam supply and condensation discharge, two valves for each 150 sq. ft. of convector surface, a total of some four hundred valves in all the hopelessness of their scattered locations, the practical outcome of the heating because of the human factor would be made quickly manifest. The cost of the equipment; exclusive of the boiler plant and tunnel equipment is estimated at about 1.5% of that of the