Coleman furnace heat exchanger problem

Old 11-06-11, 01:03 PM
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Coleman furnace heat exchanger problem

I need help. I have a Coleman furnace installed in my home. There is a large flame coming from the heat exchanger that spills out from the containment area. Subsequently I have CO readings in the house between 30 and 40 occasionally and carbon deposits on the floor in the furnace room.
When I turn the main gas valve down the unit operates properly, with no large flame.
Is this a problem with the heat exchanger (cracked?) or is it a problem with the gas valve.
Both of these were serviced about three years ago with the gas valve being replaced.
I don't want to run the furnace until I know the dangers.
I have been told that I need a new furnace. The existing one may be the original one installed in the home. Built in 1971.
Does any one have any ideas?
Old 11-06-11, 05:22 PM
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The best advice I or anyone else here can give you is to shut that furnace down & call a local pro. If your home CO detector is reading 40 ppm CO in the room air you can bet the furnace is producing a LOT higher levels. PLEASE, for your safety & that of your family shut off the power & gas to that furnace & make the call.
Old 11-06-11, 09:35 PM
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The usual cause of massive flame rollout of the kind you describe is a heat exchanger plugged up with soot due to the main burners being dirty due to lack of maintenance.

Usually its a 1-2 hour job for a repairman to clean the heat exchangers, burners and get things working again. Unfortunately, lots of repair outfits will use this as an opportunity to sell you a new furnace you don't really need.

Grady is correct that the furnace needs to be left off until repaired.

If you look in the area the burners fit into, you will probably see black soot. There are other possible causes of flame rollout, but sooting is the #1 probability.

You probably have a 75% efficient furnace. Installing a new furnace is worth considering. My personal favorite is a 90% efficient single stage condensing furnace, which most manufacturers have figured out how to build well and avoids a lot of complexity and expensive parts needed for marginally more efficient furnaces.

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