| 摘要 |
PURPOSE:To perform a wide-range combustion by means of first and second burners, by providing a first burner, a flame rod, disposed in the flame of the burner, and a control circuit, controlling combustion of a second burner according to a flame current value flowing from the flame rod through flame. CONSTITUTION:When quantities of high temperature hot water is fed, a first burner 1 is ignited. Thereafter, a control circuit 13 controls a proportional valve 5 to provide combustion in the first burner 1 with a maximum combustion amount B4. When a flame current value, flowing from a flame rod 18 through flame 19, is increased to A5, a capability switching valve 4 is actuated to start combustion of a second burner 2. Fuel fed by the proportional valve 5 is branched into the first and second burners 1 and 2, and since a combustion amount of the first burner 1 is decreased, a flame current value is also decreased to A3. Further, combustion amount is increased to a maximum combustion amount B6 in the first and second burners 1 and 2, and the control circuit 13 continues combustion under a state in that the flame current value is kept at A6. When hot feed water temperature S2 is increased to about set temperature S1, the control circuit 13 controls the proportional valve 5 to gradually decreases an amount of the fuel fed to the first and second burners 1 and 2. |
