| 摘要 |
PROBLEM TO BE SOLVED: To increase the flow rate of water to be heated while generation of the drain in a main heat exchanging part is prevented by feeding a part of water heated by a sub heat exchanging part to a water pipe on the downstream side of the main heat exchanging part, and providing a bypass circuit to be branched from the upstream water passage side of the main heat exchanging part. SOLUTION: Water to be heated flowing in an upstream end 111b of a water pipe 11b constituting a sub heat exchanging part 1b flows through the sub heat exchanging part 1b, and then, is distributed to a water pipe 11a side and a bypass circuit 15 side of a main heat exchanging part 1a, and the amount of water to be heated flowing in the main heat exchanging part 1a is reduced by the amount of water to be distributed to the bypass circuit 15. The exhaust gas from a gas burner 3 is difficult to cool at the main heat exchanging part 1a. Generation of drain in the main heat exchanging part 1a can surely be prevented and the amount of heated water to be fed to the heat exchanger 1 can be increased compared with the conventional system having no bypass circuit 15. |
