The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

Hot Water Suply

Electric water heaters generally have thermostats that simply turn the current on or off. Where by agreement water is heated only during off-peak hours and is stored for use during other hours, there may be a time switch in addition to the thermostatic switch. Where domestic water is heated by transfer from the water of a house-heating boiler, a throttling valve responding to variations in the outgoing domestic-water temperature may be installed in the circulating pipe from the house-heating boiler to the transfer device. Where a steam- heated manifold is placed inside the storage tank, the temperature may be controlled by a valve in the steam supply pipe.

40. Typical Temperature-Control System.—A typical arrangement of an installation in which the storage 'tank is heated by a steam-heated manifold is shown in Fig. 17. In this arrangement a thermostat a is screwed directly into the tank through a tapping at b. A copper tube c connects the thermostat with a metal bellows d. The thermostat o, the tube c, and the bellows d are hermetically sealed. A liquid that vaporizes at a low temperature is enclosed in the thermostat a. When the water in the tank becomes heated, vapor generated in the thermostat increases the pressure in tube c and the bellows d, thus expanding the latter by overcoming the counterpoise weight f and closing a balanced valve g.

When the water in the tank cools slightly, some of the vapor in the thermostat a condenses, reducing the pressure and allowing the bellows to collapse and open the valve g on the steam-supply pipe to the coil. By adjusting the weight / on the lever e, the standard regulators can be made to operate at any desired temperature between 140° and 200° F. When desired, these regulators can also be had to operate at other temperatures. They can be furnished with tension springs instead of the lever e and counterpoise weight .

The proper location for the thermostat a, when applied to a tank heated by a steam coil, is in the end tapping about as shown, although, when the condition warrants it, any tapping at about the same level may be used.