Mechanics of the Household / A Course of Study Devoted to Domestic Machinery and Household Mechanical Appliances

by E. S. Keene

In Fig. 174 is shown a heating and ventilating system in which the air conditioning is accomplished by automatic regulators for both temperature and humidity. The plant occupies a room in the basement, and a room directly above illustrates the conditions that prevail in all of the other rooms of the building. The principal features of the plant are the fan G, which supplies the air; the hot-air furnace H, which furnishes the heat; and the water spray S, which provides the moisture with which the air is humidified.

Fig. 174.—Furnace blast system of heating, with temperature regulation and humidity control.

The air is drawn in at A to a room in which a motor-driven fan G forces the supply through the heating apparatus into the building. The air after leaving the fan passes through a cold-air duct C to the heating surfaces H to be warmed. The air in passing over the heating surfaces is raised to a degree considerably above the temperature of the rooms. The hot air leaving the heater H enters the tempered air chamber T through the passage K. A damper M provides means for also admitting cold air to the chamber T directly from the fan. The thermostat, located at O, is connected with a pneumatic motor V (similar to Fig. 170) which regulates the supply of cold and hot air from K and M to suit the desired temperature of the air supply for the rooms above. The arm of the motor V is so arranged that an upward movement opens the cold-air and closes the hot-air passages; the downward movement produces the opposite effect. The motor V thus controls the temperature of the air.

In this system the air is humidified by a direct water spray marked S in the drawing. A part of the hot air from the heater H may escape through the damper W and absorb water on its way to the duct D, which takes the air to the room above, where it enters through the register E. This air as it comes from the heater, being hot, will absorb a larger amount of water than the air could hold when cooled to room temperature; for this reason only a part of the air supply is humidified. The supply of the hot humid air is admitted to the duct D in such quantity as will produce the desired degree of humidity in the rooms.

The degree of room temperature is governed by the thermostat, in the room, which, by means of the motor N, controls the damper F. This damper admits hot humid air and the tempered air from the chamber T in proper proportion. At any time the humidity of the air in the room reaches the maximum amount for which it is set, the humidostat, through its motor, closes the valve R, which controls the water supply to the spray nozzle, and the moisture in the air is reduced until a further amount is demanded. With apparatus of this kind the temperature and humidity may be kept practically constant.

Fig. 175.—Direct steam heating system with mechanical fan-blast ventilation, temperature regulation and humidity control.

Fig. 175 shows another arrangement of a similarly controlled plant in which steam is used for humidifying the air. The air is admitted at A, from whence it passes through a steam-heating coil S, which raises it to a predetermined temperature. The steam jets are arranged at H, for providing the necessary moisture. The humidostat through a motor valve V governs the amount of steam that is permitted to enter the humidifying chamber. A thermostat located in the air duct at B controls the temperature of the air sent to the rooms by regulating the amount of heat given out by the steam coils S. This control is made still more sensitive by use of a cold-air bypass. The damper D is opened by a motor valve to admit cold air at the same time the steam is shut off from the heater coils.

In this plant the ventilating air is not intended to supply all of the heat to the rooms. A thermostat on the wall controls the room temperature by regulating the amount of steam admitted to the radiators. In the ventilating plant previously described, all of the heat for the building is supplied through the ventilating system; in the plant shown in Fig. 175, the heating apparatus which warms the building is entirely separate and may be used when the ventilating system is inoperative.