| 摘要 |
PROBLEM TO BE SOLVED: To eliminate various kinds of inconvenience which occur when a water heater is started for hot-water supply while the water heater is operated for antifreezing. SOLUTION: An antifreezing device is used for such a water heater that a reheating and circulating circuit and a hot-water supplying circuit are heated by means of a common combustion burner in a one-boiler two-circuit heat exchanger can body, and a heating circuit is branched from the midpoint of the reheating and circulating circuit through a three-way selector valve. In the case the outside air temperature or the temperature of water staying in the heating circuit drops to a freezing preventing temperature (S3 and S4) while the operation of the water heater for heating and bath is stopped (S1 and S2), a circulating pump is started when the operation of the water heater for hot-water supply is being stopped (S5 and S6). The object of the antifreezing operation of the water heater is switched to heating and bath or heating only in accordance with discriminated results of circulation (S7, S8, and S9). After the circulating pump is operated for a prescribed period of time, the pump is returned by stopping the pump for a prescribed period of time (S10-S12). When the water heater is started for hot-water supply while the water heater is operated for antifreezing, the circulating pump is forcibly stopped by omitting the steps S6-S12.
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