| 摘要 |
PROBLEM TO BE SOLVED: To prevent the freezing without damaging the inside of a water receiving tank by providing a circulating pump for circulating water stored in the water receiving tank and a temperature sensor for actuating or stopping the circulating pump when a water temperature in the water receiving tank or outside air in the vicinity of the water receiving tank becomes an optional temperature. SOLUTION: A second water supply port 5 and a second water discharge port 6 for circulating water 2 in a water receiving tank 1 are connected by piping, and a small circulating pump 7 is arranged in the middle of these. A temperature sensor 9 for detecting a water temperature in the water receiving tank 1 is installed between the circulating pump 7 and a driving power source 8. When the water temperature in the water receiving tank 1 becomes a prescribed value or less, the temperature sensor 9 is actuated, and the circulating pump 7 is operated to suck the water 2 in the circulating pump 7 from the second water supply port 5 to be returned to the water receiving tank 1 from the second water discharge port 6 via the piping. When the water temperature becomes a prescribed temperature, the temperature sensor 9 is turned off, so that the circulating pump 7 stops to thereby prevent freezing of the water in the water receiving tank 1 without damaging the water receiving tank 1.
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