| 摘要 |
PURPOSE:To provide a hot water with good temperature characteristics, by cancelling or shortening a prepurge movement sequence in response to the frequent start and stop operations of combustion. CONSTITUTION:When a water heater once performs a normal operation and shifts into a combustion operating condition, the combustion flame is detected by a flame detecting circuit 10 and an electric current flows to a time constant circuit 16 via a diode 11 for charging a condenser 13 via a resistor 12. When the charging voltage increases to a preset reference voltage of level detection circuit 15, an output signal 22 is sent to a prepurge timer circuit 20. The prepurge timer circuit 20 is adapted to normally begin functioning in response to a combustion starting signal 21 outputted from an operation switch connected with a water cock in unison, but has the function to cancel the timer movement or to turn the counting time of timer quickly for shortening it, when an output signal 22 is received. Therefore, the prepurge movement sequence is interrupted or shortened, when there is only a short period between the counting end of previous combustion movement and the subsequent combustion movement start-up, that is, when the start and stop frequency increases, and as a result the ignition movement can be initiated in a short time period, and thereby obtaining good hot water characteristics without the chance of hot water being fell down. |
