| 摘要 |
PURPOSE:To prevent water in a pipe line from freezing by preventing heat loss as much as possible, by using some quantity of hot water from a hot water tank by opening a directional control valve to the side of a hot water tank by a signal from a temperature sensor which senses the lowest temperature in the part of a pipe line. CONSTITUTION:A temperature sensor 16 senses the water temperature between the suction port of a water circulation pump 4 and the connecting part 8a of a pipe line with a water feed pipe line 8, where the water temperature is the lowest in the pipe lines 3a and 3b. When the sensed water temperature is under the set value, the pipe line is prevented from freezing by circulating the remaining cold water out of the pipe line 3b, by driving a water circulation pump 4 by a signal from a controller 12. When the water temperature goes down under the secondary set value which is lower than the primary set value, a three-way valve 18 connects ports (a) to (b) and drives the water circulation pump 4 for a predetermined time. Hot water is fed into the pipe line 3b from the tank 2 and in the meantime, the water temperature reaches a set value for the temperature sensor 16. The time is to be determined as short as possible in order to prevent heat loss from hot water in the hot water tank 2. When the water temperature is heightened above the secondary set value, the three-way valve 18 is changed to connects ports (a) to (c), the pump 4 is driven for a predetermined time in order to circulate water bypassing the hot water tank 2. |
