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Gas Burner Safety only shuts flow of gas - burner still operates
After some work had been done on a gas burner, I noticed that when the system hit the operating set-point for pressure (3.5 lbs), the flow of gas stopped; but the burner operation otherwise continued. When the pressure fell below the differential (1 lb), the gas flow and flame resumed. This happened repeatedly. I called back the mechanic and he said a contact was loose and fixed it. Presently, the burner does completely shut down and resume flame in a proper manner. My specific question: Is it possible that the mechanic addressed only the shutdown sequence for when the operating pressure set-point has been reached and failed to check the safety device which scans for flame in the furnace? When a flame is not detected during operation of burner, shouldn't a separate safety device shut the burner operation and flow of gas simultaneously? I am concerned for the future safe operation of this furnace. Thanks in advance