Did oversized venting pipe kill our furnace?

11 years ago

I posted earlier this week about our 4 year old Carrier furnace problems. The first tech said we have a cracked heat exchanger. The second one, a certified Carrier man, told us the vent pipe extension is too big and caused soot to block the heat exchanger. He claims there is no crack, just bad blockage. The 2 inch pipe coming out of the furnace is connected to a 3 inch pipe. There is about a 12 foot run to the basement wall exit hole. Tech number two called Carrier and was told that the extension pipe should also be 2 inches if the pipe is less than 15 feet long. Both men say we need a new furnace. Would the wrong size pipe cause the furnace to stop working? My husband thinks that the installer or builder should be responsible for at least part of the replacement cost if the furnace quit due to improper installation. Any chance of that happening? Do we need a third opinion?

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Comments (5)

mike_home
11 years ago
I am skeptical about both your techs. I don't understand how a larger vent pipe can create soot and block the heat exchanger, and that if the pipe were 3 feet longer there would have been no problem. If you have a build up of soot, then you may have a chimney draft problem. I could be wrong, but I doubt the draft problem is being caused by the 3 inch diameter. My 40 gallon hot water heater has a 4 inch vent pipe!

If the heat exchanger is not cracked, then why is tech number two recommending a new furnance? Why can't vent pipe be fixed if that is the actual problem?

You should have the original contractor come in and review the installation. If as you say the installation did not follow Carrier's guidelines, then you have a good arguement about getting him to fund the repairs or replacement.
indygal
Original Author
11 years ago
The second tech said that if the furnace was vented through the roof, the 3 inch pipe would be fine. Ours is vented through the basement wall. There are several pages about venting pipe size in the manual and my husband is trying to figure out what should have been used. I guess the next step is having the installer come out. We really didn't want to use them as we've had several issues with other installation mistakes they made. We'll see what they say and then decide if we trust their installers enough to make this right.
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tigerdunes
11 years ago
Agree with Mike...sounds very fishy...
indygal
Original Author
11 years ago
Not only would the vent pipe need to be redone, but the heat exchanger would have to be replaced as it is supposedly plugged up with soot. I think they cost almost $900. I don't think it would be a good idea to put over $1,000 into a furnace that might break down again any time. Other parts could be damaged from the excess heat. The work that needs to be done would void what warranty we have. We're hoping to get the company that installed it to come look at it on Monday.
THN3363
11 years ago
Did your venting get resolved? little late but always interesting. I am a Mechanical Contractor in Florida and provide training to contractors within this state for both private and public entities......
Todd