Gas fired appts. ignition, monitoring and control equipment - has master valve closed by output control thermostat operated low load cut=out

摘要

The ignition, monitoring and control equipment for gas fired apparatus is basically conventional with an electro-magnet controlled master valve (20) and thermostat (43) control for the main throttle valve (34). However the thermostat operated bellows (42) on that valve are also mechanically linked (75) to a switch (52) in the power supply (65) to the control box (26). If heat demand drops so low that, after closure of the throttle valve, and gas flow through a bypass set to min. safe burner firing rate is still excessive, the bellows continues to expand and opens this switch, releasing the master valve.