| 摘要 |
PURPOSE:To ensure safe operation of a water baciler by detecting no-water burning thereof and preventing automatic restarting of it after water supply by a construction wherein a manually reset type safety circuit adapted to be actuated when disconnection of a hot water temperature controlling element occurs is commonly used and an inexpensive automatic reset type thermostat is provided at the boiler wall. CONSTITUTION:The arrangement is made such that when the bolier is operated without water therein a hot water thermister 7 detects it, and even if the combustion is stopped the temperature on the boiler wall rises continuously because of overshooting, an automatic reset type bimetal thermostat 6 is actuated to open its contact. Conseuently, an operational amplifier 16 receives a positive input higher than a negative input and generates an output 1 which turns a transistor 27 ON. As a result, an electric power is supplied to a resetting side coil 3 to hold a contact 4 open. In brief, even if the temperature on the boiler wall drops and the thermostat 6 resets to close its contact, the contact 4 is kept open and accordingly the boiler operation cannot be resumed. |
