| 摘要 |
PROBLEM TO BE SOLVED: To prevent all of independent channels from being frozen by providing a changeover control means for switching a channel switching valve for specific time after a circulation pump is activated by a circulation pump activation means. SOLUTION: When temperature being detected by a temperature sensor 25 is equal to or less than a freezing prevention temperature, a circulation pump 6 is activated. After the circulation pump 6 is activated, a channel switching valve 15 is changed for specific time, thus changing a water current for the specific time for passing water in each of circulation channels that is allowed to independently branch like a downstream-part water return pipe 13 for jet or reheating and a downstream-part water return pipe 14 for washing, and the freezing of each channel is prevented. Also, in freezing prevention operation, it is judged whether temperature T being detected by the temperature sensor 25 is lower than a fixed temperature T2 or not. Then, when the temperature T is lower than the temperature T2, the circulation pump 6 is activated, a heater 9 is activated by a heating control means, and a heat exchanger 8 is heated. As a result, water in a return water heating pipe 10 may be heated.
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