Taking the proportional gas burner as an example, its working process has four stages: preparation stage, pre purging stage, ignition stage and normal combustion stage.

Preparation stage: after the program controller is powered on, the internal program self-test is started. At the same time, the servo motor drives the damper to the closed state. After the program self-test, it is in the standby state. When the thermostat, too high and too low gas pressure switch, steam pressure switch of steam boiler and other limit switches are allowed, the program controller starts to start and enters the pre purging stage. If the solenoid valve group is equipped with a leakage detection system, the system will carry out valve leakage detection first when the above limit switch allows, and then enter the pre purging stage after passing the detection.

Pre purging stage: the servo motor drives the damper to the high fire opening state, and the fan motor starts to supply air for 13 seconds to blow in air for pre purging. According to the difference of the program controller, about 20-40 seconds after purging, the servo motor drives the damper to the ignition opening state to prepare for ignition. In the whole pre purge stage, the air pressure switch measures the air pressure. Only when the air pressure is kept at a high enough level, can the pre purge process continue.

Ignition stage: after the servo motor drives the damper to the ignition opening state, the ignition transformer cuts in and outputs high voltage to the ignition electrode to generate ignition electric spark. About 3 seconds later, the program controller sends power to the safety solenoid valve and proportional solenoid valve. After the valve is opened, the gas reaches the combustion head, mixes with the air provided by the fan, and is ignited. Within 2 seconds after the valve is opened, the ionization electrode shall detect the presence of flame. Only in this way can the program controller continue the following procedure. Otherwise, the program controller will lock and disconnect the solenoid valve to stop