At the time of starting a hot water discharge operation, a controller determines whether the first operation was made after the power source is switched on in S 1 , and the controller determines whether 5 minutes have passed after the previous operation in S 2 . When the first operation was not made or 5 minutes have lapsed after the last operation, the controller determines whether a difference between a detected temperature acquired by a thermistor and a preset temperature is more than 10° C. in S 3 . When a temperature difference is more than 10° C., a water flow rate servo is set at a position where a flow rate of flowing water is reduced from a determined flow rate by a predetermined amount in S 4 , and the controller performs a temperature control of discharged hot water in S 8.
1. A water heater comprising:
a burner connected with a gas supplying pipe;
a heat exchanger connected with a water supplying pipe and a hot-water discharging pipe and heated by the burner;
a water flow rate control unit provided at the water supplying pipe and controlling a flow rate of flowing water in the heat exchanger;
a temperature detection unit for detecting water temperature in the hot-water discharging pipe;
a gas pressure control unit provided in the gas supplying pipe to control a flow rate of gas supplied to the burner; and
an operation control unit controlling a temperature of discharged hot water so that a detected temperature acquired by the temperature detection unit agrees with a preset temperature by control of combustion of the burner and an operation of the water flow rate control unit, wherein:
the operation control unit compares the detected temperature with the preset temperature and when the detected temperature is lower than the preset temperature by a predetermined degree, the water flow rate control unit immediately reduces the flow rate of the flowing water from a previously determined flow rate of flowing water at a point of time that discharged hot water is required and then the gas pressure control unit immediately reduces the flow rate of gas according to the flow rate of flowing water; and
the operation control unit performs the temperature control of the discharged hot water.
2. The water heater according to claim 1 , wherein the operation control unit sets back the flow rate of flowing water of the water flow rate control unit to the determined flow rate when the detected temperature approximately agrees with the preset temperature in the temperature control of discharged hot water.
3. The water heater according to claim 1 , wherein the operation control unit sets back the flow rate of flowing water of the water flow rate control unit to the determined flow rate when a predetermined period of time elapses after the point of time that discharged hot water is required.
4. The water heater according to claim 1 , wherein the operation control unit compares the detected temperatures with the preset temperature immediately at the point of time that discharged hot water is required.