| 摘要 |
A first period during which drain is not substantially generated on a surface of a water tube ( 4 ) of a heat exchanger (B 1 ), and a second period as a transition during which an amount of drain on the surface of the water tube ( 4 ) is increased are provided. There are a plurality of kinds of fan-controlling data in which operation control contents of the fan ( 13 ) in the first and second periods in correspondence with change of conditions of entering water temperature or combustion level of the burner ( 1 ). The fan-controlling data are stored in a data table ( 90 ) of a controller ( 9 ). The controller ( 9 ) controls the fan ( 13 ) in accordance with the data, and an initial air-fuel ratio of combustion driving of the burner ( 1 ) is stabilized. |
