| 摘要 |
<p>PURPOSE:To positively prevent water in a circulation circuit from freezing without using other parts such as valves, heaters and the like by starting a circulation pump when an antifreezing thermostat of the circulation circuit detects a freezing critical temperature, and stopping the operation of the circulation pump after the passage of a first set time from a time when the anitifreezing thermostat detects a certain temperature which is greater than the freezing critical temperature. CONSTITUTION:When the detected temperature Ti of a temperature sensor 19 becomes more than a set temperature Ts, a warm water thermostat 27 turns off output switches 271 and 272. The power supply of a burner controller 32 is cut off and the burner 11 stops to burn. Also, after the passage of 45 seconds from a time point when the burner 11 stops to operate, a timer switch 281 is turned off, and the power supply to the pump controller 28 is cut off. For this reason, during 45 seconds, the operation of a circulation pump 7 is continued to prevent the heating within a heating unit 10 due to after-heating. Further, when a pump 7 is operated at a minimum flow amount, the timer device 28 is set at a water outlet 5 is set at a time required for reaching a warm water return port 6, and this warm water in a circulation circuit 4 can be completely recovered to a hot water storage tank 1.</p> |
