| 摘要 |
PROBLEM TO BE SOLVED: To compensate a drop of a hot water supply temperature due to a heat absorption of circulating hot water from a water heating heat exchanger side to a supplementary burning heat exchanger side occurring at the time of simultaneously operating a water heating function of single-can two-water channels and a supplementary burning heat exchanger function of bathtub water by a reduction control of a circulating flow rate to a circulating pump. SOLUTION: A circulating pump 13 provided at a circulating passage of supplementary burning is constituted by a DC pump. At the time of simultaneously operating water heating and supplementary burning of bathtub water, when a request combustion capacity of the water heating exceeds an aligned maximum capacity of the water heating side so that a water heating temperature lowers from a set water heating temperature, a DC driving power to the pump 13 is lowered to control to reduce a circulating flow rate of the supplementary burning. A circulating pump 20 of a DC type is adopted, and hence a flow rate of the pump is controlled to be reduced from zero of the flow rate to a wide range up to a rated flow rate, and hence a drop of the water heating temperature due to a heat absorbing amount from a water heating exchanger 2 side to a supplementary burning heat exchanger 3 side is accurately controlled. |
