| 摘要 |
PURPOSE:To prevent readily and positively a water heater from being frozen without letting water remain running, by connecting a water supply conduit and a hot water delivering conduit of a heat exchanger through by-passes, and circulating water in the heat exchanger by a motor pump in case the freezing is apprehended. CONSTITUTION:A boiler body W is connected with a tap 12 via a hot water supply piping 11. A by-pass 13 branched from the hot water delivering conduit 8 of a heat exchanger 1 is connected with the outlet of a motor pump 14. The inlet of the motor pump 14 is connected with the water supply conduit 6 through a by-pass 15. Thus, in normal operation, when the tap 12 is opened or closed, a water flow switch 4 responds to it to serve hot water. The motor pump 14 is controlled by the signal from a thermostat 16, in case the tap 12 is closed, that is, in case the heat exchanger is not in operation. When ambient temperature of the heat exchanger 1 has lowered to a freezing range, the thermostat 16 causes the motor pump 14 to be driven, so that the water in the heat exchanger 1 is circulated via the water supply conduit 6 and the hot water delivering conduit 8 and therefore the water is prevented from freezing. |
