| 摘要 |
PURPOSE:To make it possible to constantly supply hot water of a set temperature even the water feed temperature is changed, by providing a temperature detecting portion on the water pipe of a heat exchanger, connecting a water pipe bypassing a heat exchanger located on the upstream side from the temperature detecting portion to the downstream side from the temperature detecting portion, and setting an amount of water so that the ratio between the amount of water passing through the upstream side heat exchanger and the amount of water passing through the bypass water pipe becomes substantially equal to the ratio between the heat absorbing amount of the upstream side heat exchanger of the temperature detecting part and that of the downstream side heat exchanger. CONSTITUTION:At an intermediate position between an upstream side heat exchanger 6a and a downstream side heat exchanger 6b is provided a temperature detecting portion 8 so that a gas proportional control valve 3 is automatically adjusted by a feedback control device 9 in accordance with the detected temperature. Further, a bypass water pipe 10 bypassing a heat exchanger 6 from a supply water pipe 5 and connected to the outlet side of the heat exchanger 6, is provided. For example, an orifice 11 is provided on the bypass water pipe 10 so that the ratio between the amount of water passing through the upstream side heat exchanger 6a and the amount of water passing through the bypass water pipe 10 is substantially equal to the ratio between the heat absorbing amount of the upstream side heat exchanger 6a of the temperature detecting portion and the heat absorbing amount of downstream side heat exchanger 6b thereof thereby to set the amount of water passing through the bypass water pipe 10 and the amount of water passing through the heat exchanger 6.
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