| 摘要 |
PROBLEM TO BE SOLVED: To provide a water heater capable of preventing durability from lowering during a standby for preheating a premixing type burner by automatically driving a bypass opening and closing valve. SOLUTION: This water heater is provided with a hot water supply pipe 4 provided in downstream of a heat exchanger 1, a bypass pipe 5 branched from the water supply pipe 2, bypassing the heat exchanger 1 and joining the hot water supply pipe 4, a bypass opening and closing valve 6 provided in the middle of the bypass pipe 5, a temperature setting means 11 setting a desired hot water supply temperature, and a standby circuit 13 holding the premixing type burner 10 in a standby state at vaporizable temperature for a specified time. The bypass opening and closing valve 6 is opened by that a flow rate sensor 8 provided in the hot water supply pipe 4 detects a specified flow rate during a standby, and closed by that a hot water supply thermistor 9 maintains temperature over a set water-heating temperature and below the specified temperature determined by the set water-heating temperature for a prescribed time. Thereby, the durability of peripheral parts and the opening and closing valve itself can be excellently maintained and burn risk can be surely prevented too. COPYRIGHT: (C)2004,JPO
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