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marion60 11-01-2011 12:58 PM

main burner goes out after furnace running 10 -2 0 mins
I got frustrated with my gas furnace this week after I tried to fix it a couple of times. The details are below:

Gas Furnace: Rheem Criterion RGDG-100BRJR installed 1992. It's probably Rheem Criterion I.
1. Thermostat always shows Low Battery - Fixed it with installing new one.
2. Pilot burner was out - I found this problem before turning heat on. Tried to light it a couple of times but went out again after I released control knob. I cleared it and lighted again, it works fine and keeps flaming.
3. No main burner light - when I turn heat on from thermostat, everything seems to work fine but main burner which didn't light. I opened blower door and found a loose wire connecting transformer with control board. I tightened it and turn heat on again, main burner worked. The furnace worked fine for a whole night with on and off several times.

Second day, I thought loose wire was a problem that I already fixed. So I replaced filter with new one and closed burner compartment door. However when thermostat turns it on, main burner lighted and went out again in 10 or 20 minutes. If I opened burner compartment door or blower door, it may get main burner lighted again. If I turn heat off for a while and turn on again from thermostat, main burner works fine. Of course, it will go out in 10 - 20 minutes. Obviously something shuts off gas to main burner while pilot keeps flaming.

Is this Negative Pressure Control problem? I did check the rubber tube, which is clean. When sucking and blow tube, I can hear click. Can I bypass NPC by wiring two wires together to test if it's NPC problem? Why main burner flames just 10 - 20 minutes? Or what else shut off gas for main burner in 10 - 20 minutes? Is it something to be blamed when temp raises in 10 to 20 minutes?

Any input would be appreciated.

biggles 11-01-2011 02:07 PM

filter is clean as you said just pulling the fan accesss door off and it relights or stay lit says the heat exchanger is going into hi limit trip on the burner...that negative air thing is too deep for a residential furnace you have return air problems.......:eek:eye ball that squirrel cage for dirt or dust rounding off the fins.... lack of air causes heat to rise into hi limiting situation main burner shutdown

beenthere 11-01-2011 02:23 PM

If you have central A/C, the evap coil may be dirty.

marion60 11-02-2011 09:02 AM

Thanks, biggles and beenthere. Both's suggestions do be what I was worry. I checked return air pipes and tested them with smoking and they seems clear. When I tried to check evap coil, it seems unaccessible as it's surrounded by pipes. I am sure it's dirty as it's 20 years old and I don't think it was cleaned before.

Now it's warm up. Furnace works fine for on/off test for short period. Obviously return air/vents are what I should pay attention to. Thank your both again.

biggles 11-02-2011 09:53 AM

coil check..standing in front of the furnace the "A" looks like this looking at the top of the furnace... go to the back side and cut an inspection hole at the bottom of the "A" go slow "NO DRILLs".i am trying to get you into the area so you can peel that duct like a flap and bend it out to get a mirror and flash light in there you need to see the inside part of the coil where the air comes up from the fan...before any cutting do this....:wink:how are the fins on the squirrel cage of the main fan run your index finger on them if there clean the coil will be just dusting not enough to limit the fan during the heating

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