On large work it is essential to satisfactory service to provide automatic control for the hot-water tank. On smaller work, also, automatic control may be used to advantage. When the supply system is under the attention of a painstaking attendant the necessity of automatic regulation is not so great, but in general constant attention to the necessary requirements cannot be depended upon, in which case control of the temperature of the hot-water supply by automatic means avoids all trouble.
There are several excellent systems of regulation now on the market, two of which are shown in the several illustrations of Plate 55. Fig. A represents a sectional view of one of these regulators for use in connection with boilers heated by kitchen range or special tank heater. Fig. B shows this regulator in use in connection with a boiler heated by tank heater. The regulator should always be connected to the flow pipe, and may be in either a horizontal or vertical position. In using this regulator, the part B is filled with water through the opening D, which is closed by means of a plug. About a cupful of water should be drawn out through a small tube, and this liquid replaced by an equivalent amount of gasoline.
Plate LV. Automatic Control Of Hot-Water Tanks
Automatic Control Plate 55.
of Hot Water Tanks
The hot water of the flow pipe which passes through C, C, heats the contents of B to the temperature of the hot water itself.
Gasoline has a somewhat lower boiling point than water, and will boil just before the water in B and C, C, reaches the boiling point. The gasoline in boiling exerts a pressure which is transmitted through A to a diaphragm, which in turn, by means of a lever, operates the chain which will close the draught damper and open the check damper. When the temperature of the water has dropped sufficiently, the diaphragm will react, opening the draught damper and closing the check.
The regulator may be set at any convenient point in the flow pipe, the only requirement being that it be set so that the plug D shall be at the top, in order that it may be filled.
Fig. C shows the regulation of live and exhaust steam to the steam coils when the boiler is to be heated in this way.
The regulator is connected into the end of the boiler and about three-quarters of the distance up from the bottom. This regulator should be set horizontally, with the tube running into the boiler. A diaphragm steam valve is placed on the steam-supply pipe, at a point between the boiler and the live-steam connection, in order to control both live and exhaust steam. City pressure is connected to the regulator, and thence to the steam valve. Before reaching the regulator the water supply is reduced to the proper pressure by a filter. As the temperature of the tank water rises, the expansion of the tube inside the boiler operates the regulator, which allows the water pressure to reach and close the steam valve, thus shutting off the supply of exhaust steam to the coil.
When the water cools, the regulator acts in an opposite manner, the city pressure is shut off, and the water carried away from the steam valve through the waste.
On the live-steam connection the regulating valve is adjusted to open at a lower temperature than that usually carried in the exhaust-steam pipe. Thus, when the latter falls below its normal point, live steam is admitted through the steam valve.
If a tank heater is also connected to a boiler thus supplied, the regulator shown in Fig. B may be used in conjunction with the regulating apparatus of Fig. C.
The regulator of Fig. D is of another make, but working along similar lines to the regulator of Fig. C. By means of this regulator any desired temperature of the water may be obtained by moving the pointer toward " cooler " or " warmer."
By means of a diaphragm similar to that shown in Fig. B, this regulator can be made to control the temperature of hot-water tanks heated by tank heaters.