| 摘要 |
PURPOSE:To enable to obtain energy-saving effect as much as posible and to heat water to a desired temperature independently of the change of environmental conditions even if an electric water heater is operated by a time-limited electric power, by providing a section for detecting the amount of residual hot water, driving a timer when the water temperature or the atmospheric temperature is lower than a prescribed value and the temperature of hot water in a tank is lower than a prescribed value, and switching the heat source from a heat pump to a heater after passing of a prescribed time. CONSTITUTION:A section 15 for detecting the amount of residual hot water is furnished with an output signal of a residual hot water sensor 16 which is fixed to the wall surface of a tank 1 at a proper position from the top of the tank 1 and closes a load contact Ry4' by applying a signal to a relay Ry4 when the sensor 16 does not detect a prescribed temperature of residual hot water. Further, the section 15 is connected electrically with a water-temperature detector 11a. Here, a rrangement is such that the section 15 for detecting the amount of residual hot water is not operated insofar as the temperature of residual hot water becomes lower than a set temperature of a water- temperature sensor 11. The load contact Ry4' is connected in series to a 100V power source together with a timer 18 and a changeover switch 19, and a load contact 18a of the timer 18 is connected in series to a relay Ry1. |
