| 摘要 |
PROBLEM TO BE SOLVED: To provide a water heater, in which a burner 1 can be maintained at an optional combustion condition all the time. SOLUTION: The water heater comprises a burner 1 to which a gas 15 is supplied for combustion through a gas pipe 14 having a flow-control valve 13, a fan 11 for supplying combustion air to the burner 1, a heat exchanger 12 through which water 121 passes, a mass flow-rate sensor 21 detecting a flow rate of the gas 15 passing though the gas pipe 14, a supply-water temperature sensor 22 for detecting supply-water temperature, a water-supply rate sensor 23, and inflow-water temperature sensor 24, a supply hot-water temperature-setting device 26, a combustion controller 3, and an air-fuel ratio sensor 25. In the combustion controller 3, an aimed gas-supply rate is determined for burning at an aimed burning-rate, and a valve opening in the valve 13 is controlled so as to reach the gas supply rate detected by the sensor 21 to the target. The controller 3 feeds back the quantity of power given to the fan 11 (volume of air sent out of the fan) so as to reach the air-fuel ratio detected by the sensor 25 to the target for a stable combustion.
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