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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7585
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a DESA unvented propane fireplace and the logs wii

Customer Question

I have a DESA unvented propane fireplace and the logs wii only stay lit on the low position. Will go off on the medium and positions.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.
Welcome
That can be a dangerous situation relative to carbon monoxide production.
The person most likely used a can of compressed air to blow lint away from the pilot light.
It is most likely that when the burner comes off of its low setting, the disruption of air around the pilot light causes the pilot flame to be drawn away from the thermocouple and thermopile units mounted in the pilot assembly... causing any weak thermopile or thermocouple to fail.
The flame pattern on these needs to be examined for any such pilot flame behavior.
And the millivolt output of the thermopile measured against the millivolt rating stamped on it, and the gas valve.
http://screencast.com/t/yzRk2WjY
copy/paste that into your browser.
Configurations vary. but all include these thermocoouples and thermopiles.
The orifice is the size of a human hair, virtually impossible to clean, replacing the entire pilot light and all of its parts is a common solution.
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