Furnace Floating Flame Problem? Need Help


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Old 12-10-11, 01:14 PM
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Furnace Floating Flame Problem? Need Help

I have an Aire Flo AF90MPB Series Gas-fired condensing warm air furnace.

The furnace will light and run for about 10 seconds before the flame starts to just fizzle out. Sometimes it will jump a little bit. It goes out before the blower even comes on.

I have checked the thermocoupler and cleaned that, so I do not think it is that.

Another interesting thing is if I take the cover off of the burner compartment, it will run fine.

I am wondering if it is an air intake problem, like not getting enough air for combustion.

Any help would be greatly appreciated, it is pretty cold here.

TIA
 
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Old 12-10-11, 01:36 PM
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Floating flames are a tell tail sign of a shortage of combustion air.

Odds are that the heat exchangers are plugged with soot, which is preventing the free flow of combustion gasses through the furnace.

In any case, the furnace is unsafe to operate and should be left off until it's been inspected and repaired.

Leaving the cover off the burner compartment is an invitation for the burner flames to come out the front of the furnace and burn up wires and parts until that causes the furnace to quit.
 
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Old 12-10-11, 01:50 PM
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Thanks for the response.

I am not running the furnace with the cover off constantly, I just did it to check and see if it made a difference.

How much work is it to clean the heat exchangers. I am pretty handy and have an engineering background. I am comfortable taking thing apart and working with them. Is it something that I could do myself?
 
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Old 12-10-11, 06:29 PM
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Well, you can check the heat exchangers, located above the burners, and look for the soot I'm guessing is probably there. Use a small mirror and flashlight and see what you can see.

A sooted heat exchanger, usually caused by dirty burners, would be the most usual cause of the problem, but others things could cause those symptoms.

Cleaning a sooted condensing furnace is not something I'd recommend for a DIYer. It would involve disassembling much of the furnace and there are typically two heat exchangers including one that looks something like a car radiator which need to be removed and cleaned.

Engineers might be a special case. Not something I'd recommend, though.

Do you have the manual for the furnace? Sometimes there are directions for cleaning heat exchangers in the operating manual that might provide some guidance.
 
 

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