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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


  • lchmb
    lchmb Member Posts: 2,997
    The brand may help to better understand what we are working on...
    JUGHNE Member Posts: 8,686
    The brand of the burner.....assuming it is a power fan forced burner.
    JUGHNE Member Posts: 8,686
    I am guessing the post purge cycle must be long enough for the pressure to drop and burner come back on?
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,493
    I don’t understand how the gas flow could stop, while the burner continued its burn???
    The pressure is too high as well, but not the cause of this burner problem.—NBC