goodman furnace problems


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Old 02-14-09, 08:37 PM
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goodman furnace problems

goodman furnace mod#gun125-5b 90 plus furnace built 1989. converted to lp gas. after furnace lights and runs for approximately 2 minutes, the flame ignites inside the burner . cleaned burners and checked manifold pressure. what is the problem?
 

Last edited by levi54; 02-14-09 at 09:24 PM. Reason: better description
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Old 02-14-09, 10:39 PM
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That's called burtner flashback. Gas flames burn so many feet per minute. If the speed of the gas coming out of the burner orifice and burners is fast enough, the flame burn on the top of the burners (typically) where they should. If the velocity of the gas is too low, the flames will flash back inside the burner or in front of the orifice.

What was the burner manifold pressure you got, and check the burner orifice sizes to make sure they are correct for propane.
 
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Old 02-15-09, 06:16 AM
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goodman furnace problems

manifold pressure was 9.7 " inlet gas pressure was same9.7"
 
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Old 02-15-09, 02:37 PM
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A pilot first lights? Then it continues on pilot for 2 minutes and then the main burners light? When they do, is there a huge WOOF sound, or does it simply fire up late and seemingly fire up like normal, except delayed? Is this open(single PVC vent pipe) or closed combustion furnace(2 PVC vent pipes)?
 
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Old 02-15-09, 06:52 PM
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the main burners light right away and burn ok for two minutes then they start burning in side the burner tubes. this is a single vent pipe installation. i told homeowner to have lp gas co. raise pressure to at least 11" of wc. we will see if this helps.
 
 

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