Gas Burner Safety only shuts flow of gas - burner still operates

David L. Taylor

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

The brand may help to better understand what we are working on...

JUGHNE

The brand of the burner.....assuming it is a power fan forced burner.

JUGHNE

Hello??
I am guessing the post purge cycle must be long enough for the pressure to drop and burner come back on?

nicholas bonham-carter

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