| 摘要 |
A hot water heater having upper and lower electric heating elements and associated thermostatic switch controls in their electric circuits is provided with an energy saving control circuit for maintaining the lower heating element deenergized at all times except when it is needed to assist the upper heating element to heat the entire contents of the hot water heater tank. The energy saving control circuit includes an energy saving switch in the electric circuit of the lower heating element. A full tank relay switch is connected in parallel with the energy saving switch and the relay coil is connected to a transformer secondary winding through a holding circuit provided by a holding relay switch the coil of which is connected to the transformer secondary through a momentary make switch. The holding relay switch serves to maintain the holding relay coil connected to the transformer secondary after the momentary make switch is opened. The transformer primary winding is connected to a source of electric potential through a photoelectric cell which is activated by light to open the circuit of the transformer primary. A neon lamp light source for the photoelectric cell is connected to the lower heater thermostatic switch in such manner as to connect the neon lamp to the electric supply for the lower heater element when the thermostatic switch is opened upon attainment of a preselected water temperature sensed by the lower heater thermostat. |
