I have an airtemp furnace with a cracked het exchange.
I have an airtemp furnace and I was told by a technician that the heat exchanger has a crack in it. I thought that furnaces lasted at least ten years. Is this a common problem with these furnaces? It is a model U-32 Rev A.
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First thing I do, especially if the furnace is an older one, is to light a match or long end lighter(like for BBQ pits), hold it inside the opening on the front of the furnace heat exchanger, where you would normally see the burner flames, then turn on the fan only. If you see the "flame dance/flame disturbance", then that furnace may be unsafe due to a cracked heat exchanger. Holes or cracks in heat exchanger will blow out the pilot by allowing the air that we breathe to enter the heat exchanger and mix with the combustion process. AND may cause carbon monoxide poisoning. In that scenario, I would call in a professional. Now if it's not a heat exchanger issue, the flue pipe may have a back draft issue. Again, call a professional! Play it safe with that issue. Hope this helps!
The heat exchanger must be free of cracks and holes due to the potential of carbon monoxide leakage. You can probably make a short term repair with sheet metal and high heat furnace refractory cement, but that is a quick fix only.
Please be aware of the potential for a lethal situation due to carbon monoxide poisoning.
Check heat exchanger for cracks or holes which will cause the fan to blow out the flames. The flame sensor on the pilot or burners has to be in constant contact with flame to operate normally. If the flame is put out by a cracked exchanger the exchanger or furnace needs to be replaced.
I would only assume that now you have taken out an over heating sensor. When a heat exchanger goes bad it is a very dangerous situation because now you are pumping carbon monoxide in your house along with your heat. A heat exchanger is a baffle that hot gases pass thru, heating up the exchanger along the way and expelling carbon monoxide out the exhaust/chimney. Bad exchangers crack along seams or burn holes thru allowing the exhaust to mix with the blower air and in time this could cause carbon monoxide build up in your house. This cracking also lets hot exhaust in to the furnace and can burn up over heat protection, wiring and possibly cause a house fire. Please change out the heat exchanger or entire furnace, there is no price to replace a human life.
Think about it this way, how much more money do you want to invest in a system that can only return 70 cents in heat for every dollar you spend on fuel? Other things will fail and the dependability has already let you down. Compared to a newer system at about $4000 over a 20 year lifespan, $200 a year in fuel savings will break even your investment for a 90-95% efficient system. $800-1000 today for a replacement heat exchanger and more dollars tomorrow when the blower dies. My question is, why did the exchanger crack? Is the return air duct-work properly sized?
Are you saying you lose the pilot flame or the main burner flame? A cracked heat exchanger will cause a "venturi effect" when the blower cycles on. This effect will cause blower to interfere with combustion air and **** out the pilot, and cause lifting of the main burner flames (also add oxygen to the flames changing their color).
Some of your newer style furnaces will kick the hi limit when they have a crack in the exchanger dropping the flame and bringing the blower on.
If you are pretty confident of a crack I would suggest a water test.....After the furnace has cooled. determine which way will most easily access the heat exchanger through the top (under the a-coil) from the "plenium". or from below by removing the blower with it's housing.
once you have determined your approach get a bug sprayer and put water in it. With the heat exchanger cool, use the wand of the sprayer to liberally spray the top of the exchanger. If there is a crack the water will find its way into it. Take a flashlight and look into the bottom of each burner slot, if you see water, you have a crack, shut it down and replace it.
This sounds like a bad heat exchanger. It is possible that you do not see the crack because the crack is closed when the heat exchanger is cold (or room temp). Allow the furnace to heat up, this will allow the expansion of the crack. Turn the power off and examine the heat exchanger while it is still hot.
either you are haveing a backdraft situation or your furnace heat exchanger is cracked, What I woulc reccommend is to have a professtioal service technician checkout your furnace for a cracked heat exchanger. Thanks.
The heat exchanger is a bear to change. depending on the age of the unit it might be more practical to replace the unit. However unless you trust this service tech I'd get a second opinion, because it is rare that a heat exchanger will crack, plus by law he or she should have shut the furnace down do to carbonminoxde. Especially rare in Coleman Evcon series units.