Apparatus for monitoring gas leaks in domestic hot water system

摘要

An apparatus for monitoring the safe operation of a domestic gas-fired water heater has a gas leak detector which operates on changes in its electrical resistance in the presence of gas such as to successively energise a row of LEDs as the gas concentration increases up to a threshold level which precipitates a system trip/lock-out, a flashing LED warning and which requires manual resetting. A self-checking circuit design ensures separate flashing LED indication in the event of sensor power supply or output signal cable failure and a manual/auto changeover switch on the LED indicator unit permits temporary unmonitored operation during emergencies.