These are warmed by furnaces, direct steam and hot water. Furnaces are more often used in the smaller houses, as they are cheaper to install, and require a less skilful attendant to operate them. Steam is probably used more than any other system in blocks of larger size. A well-designed single pipe connection with automatic air valves dripped to the basement is probably the most satisfactory in this class of work

People who are more or less unfamiliar with steam systems are apt to overlook one of the valves in shutting off or turning on steam, and where only one valve is used, the difficulty arising from this is avoided. Where pet-cock air valves are used they are often left open through carelessness, and the automatic valves, unless dripped, are likely to give more or less trouble.

Apartment Houses 1000191

Fig. 37.

Greenhouses and conservatories are heated in some cases by steam and in others by hot water, some florists preferring one and some the other. Either system when properly designed and constructed should give satisfaction, although hot water has its usual advantage of a variable temperature. The methods of piping are in a general way like those already described, and the pipes may be located to run underneath the beds of growing plants or above as bottom or top heat is desired. The main is generally run near the upper part of the greenhouse and to the furtherest extremity in one or more branches, with a pitch upward from the heater for hot water and with a pitch downward for steam. The principal radiating surface is made of parallel lines of 1 1/2 inch, or larger, pipe, placed under the benches and supplied by the return current. Fig.. 37, 38 and 39 show a common method of running the piping in greenhouse work. Fig. 37 shows a plan and elevation of the building with its lines of pipe, and Fig.. 38 and 39 give details of the pipe connections of the outer and inner groups of pipes respectively.

Apartment Houses 1000192

Fig. 38.

Any system of piping which gives free circulation and which is adapted to the local conditions should give satisfactory results.

The radiating surface may be computed from the rules already given. As the average greenhouse is composed almost entirely of glass we may for purposes of calculation consider it such, and if we divide the total exposed surface by 4 we shall get practically the same result as if we assumed a heat loss of 85 B. T. U. per square foot of surface per hour and an efficiency of 330 B. T. U. for the heating coils; so that we may say in general that the square feet of radiating surface required equals the total exposed surface divided by 4 for steam coils and by 2.5 for hot water. These results should be increased from 10 to 20 per cent for exposed locations.

Apartment Houses 1000193

Fig. 39.

Care And Management

The care of furnaces, hot-water heaters and steam boilers has been discussed in connection with the design of these different systems of heating, and need not be repeated. The management of the heating and ventilating systems in large school buildings is a matter of much importance, especially in those using a fan system; to obtain the best results as much depends upon the skill of the operating engineer as upon that of the designer.

Beginning in the boiler room, he should exercise special care in the management of his fires, and the instruction given in "Boiler Accessories" should be carefully followed; all flues and smoke passages should be kept clear and free from accumulations of soot and ashes by means of a brush or steam jet. Pumps and engine should be kept clean and in perfect adjustment, and extra care should be taken when they are in rooms through which the air supply is drawn, or the odor of oil will be carried to the rooms. All steam traps should be examined at regular intervals to see that they are in working order, and upon any sign of trouble they should be taken apart and carefully cleaned.

The air valves on all direct and indirect radiators should be inspected often, and upon the failure of any room to heat properly the air valve should first be looked to as a probable cause of the difficulty. Adjusting dampers should be placed in the base of each flue, so that the flow to each room may be regulated independently. In starting up a new plant the system should be put in proper balance by a suitable adjustment of these dampers, and when once adjusted they should be marked and left in these positions. The temperature of the rooms should never be regulated by closing the inlet registers. These should never be touched unless the room is to be unused for a day or more.

In designing a fan system provision should be made for "air rotation"; that is, the arrangement should be such that the same air may be taken from the building and passed through the fan and heater continuously. This is usually accomplished by closing the main vent flues and the cold-air inlet to the building, then opening the class-room doors into the corridor ways, and drawing the air down the stairwells to the basement and into the space back of the main heater through doors provided for this purpose. In warming up a building in the morning this should always be practiced until about fifteen minutes before school opens. The vent flues should then be opened, doors into corridors closed, and cold-air inlets opened wide, and the full volume of fresh air taken from out of doors.

At night time the dampers in the main vents should be closed, to prevent the warm air contained in the building from escaping. The fresh air should be delivered to the rooms at a temperature of from 70 to 75 degrees, and this temperature must be obtained by proper use of the shut-off valves, thus running a greater or less number of sections on the main heater. A little experience will show the engineer how many sections to carry for different degrees of outside temperature. A dial thermometer should be placed in the main warm-air duct near the fan, so that the temperature of the air delivered to the rooms can be easily noted.

Care And Management 1000194

Fig. 40.

The exhaust steam from the engine and pumps should be turned into the main heater; this will supply a greater number of sections in mild weather than in cold, owing to the less rapid condensation.