| 摘要 |
PROBLEM TO BE SOLVED: To shorten operating time of a circulation pump to protect the pump while securing an instant hot water supply function.SOLUTION: A water heater includes a hot water storage tank 2, hot water supply piping 10, hot water return piping 11, a circulation pump 12, a returned hot water temperature sensor 13, an outside air temperature sensor 14, a heat pump unit 20, a control device 30 and the like. The control device 30 executes a circulation operation for circulating hot water between the hot water storage tank 2 and a hot water supply terminal 40 via the hot water supply piping 10 and the hot water return piping 11 by intermittently operating the circulation pump 12 by repeating the start and stop of the circulation pump 12 while hot water is not supplied. While the circulation operation is being executed, pump stop time from the stop to restart of the circulation pump 12 is changed based on a returned hot water temperature. Thus, while an instant hot water supply function is maintained, the pump stop time can be controlled appropriately to minimize the operating time of the circulation pump 12. |
