Control for off=peak electric water heater - has thermostatic control circuit to postpone start of heating cycle according to initial temperature of water

摘要

The supply is connected to the heating element through a thermostat, a control circuit and a time switch contact. The control circuit has a series of parallel branches each of which contains a thermostat and a cam operated contact. The thermostats are mounted at increasing heights on the water vessel and the cams are rotated by a motor. A relay closes a contact when any branch has both thermostat and cam contact closed. The cams are arranged so that the thermostats at successive heights can call for heat only at progressively later times during the off peakperiod.