Control of gas burner water heater - involves inhibition switching of gas valve to ensure that safe delay is provided before gas valve can be operated following turn off

摘要

A heating plant has a gas burner (4) that is used to heat water passed through a circulating system (3) containing heat exchangers (1). The temperature of the water is monitored (7) and the valve compared (11) with the output of a room thermostat (9). The output of the amplifier is switched (18) through to a solenoid valve (5) that controls gas flow to the burners. The operation of the switching stage is controlled by a timing unit (16) that is counter based and is coupled to a circuit that allows minimum and maximum periods for blocking the reactivation of the gas flow valve following switch off. ADVANTAGE - Prevents generation of harmful emissions during start phase.