| 摘要 |
<p>PROBLEM TO BE SOLVED: To eliminate malfunction in the case of checking a trouble by providing an enough allowance against noise. SOLUTION: A changeover switch 5 switches a setting circuit 7a of a first reference voltage, employable as a deciding reference in a flame detecting circuit 3, into a setting circuit 7b of a second reference voltage, having a level non-available normally, temporarily during combustion. In this case, when the flame detecting circuit 3 has decided that 'flame exists', an abnormality checking circuit 4C judges that the flame detecting circuit 3 is faulty whereby a main control unit 4A flashes an abnormality informing lamp 6 and closes a solenoid valve V.</p> |
