| 摘要 |
PURPOSE:To prevent combustion noise caused by resonance, by decreasing the voltage to be applied to a control valve which control the combustion rate of a secondary burner at a predetermined rate when a voltage distributor becomes conductive by the drive of an actuator when a primary burner is in the state of combustion. CONSTITUTION:When an operation switch 14 is closed, a solenoid valve 12 is opened to bring a primary burner 11 into combustion, and at the same time the contact point of an output as a switching means 4 is closed and the voltage to be applied to a transistor from an operational amplifier 24 is decreased as much as a predetermined rate because a fixed resistor is connected between them. Accordingly the actual maximum combustion rate is decreased at the predetermined rate, even if the output corresponding to the maximum combustion rate of a secondary burner 21 is produced in the operational amplifier 24 in relation to the set temperature by a temperature setter 23 and the output rate of hot water. The decrease of combustion rate is previously set, so that the maximum combustion rate of a secondary burner 21 is decreased to the degree that combustion noise by resonance will not be produced under the conditions that both the primary burner 11 and the secondary burner 21 are in the state of combustion, taking the conditions of an exhaust hood 3 and so forth into consideration. |
