| 摘要 |
PROBLEM TO BE SOLVED: To improve the efficiency of heat exchange by passing water in a branched manner to a main heat exchanger and an auxiliary heat exchanger, and controlling the water flow quantity to branched pipes at least according to either the supply quantity of hot water or the combustion quantity of a burner. SOLUTION: Water to be fed is branched on the upstream side of a main heat exchanger 2 and an auxiliary heat exchanger 4, and passed into a water pipe 3 and a branched pipe 5. The water fed into the branched pipe 5 and the water fed into the water pipe 3 is respectively heated in the auxiliary heat exchanger 4 and in the main heat exchanger 2 respectively, and then, merged to each other, and supplied from a hot water supply pipe. A flow rate control valve 9 is provided on the upstream side of the auxiliary heat exchanger 4 in the branched pipe 5 to control the water flow quantity to the main heat exchanger 2 and the auxiliary heat exchanger 4. When the requested quantity of hot water to be supplied is small, and the combustion quantity of a burner is small, the flow rate control valve 9 makes a control so that the water flow quantity to the auxiliary heat exchanger 4 is increased. On the contrary, when the requested quantity of hot water is large, and the combustion quantity of the burner is large, the water flow quantity to the auxiliary heat exchanger 4 is decreased, and the water flow rate to the main heat exchanger 2 is increased. |
