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Thread: Carrier Furnace causing exhaust smell inside house

  1. #1
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    Carrier Furnace causing exhaust smell inside house

    Situation:
    2 year new Carrier Gas Furnace (Two stage, variable speed ECM, Condensing Gas Furnace, model 59TP6A)
    Exhaust smell in house when furnace is on (getting worse for 2 months)
    It smells like dirty combustion, and causes sore itchy throat
    No outside or garage smells are present

    HVAC Technician investigation so far, yielding no root cause in 3 visits:
    Checked exhaust and air intake system, and cleared with high pressure air
    Checked blower fan
    Checked burners (glowing steady blue)
    Changed air filter 3 times in 3 months
    Checked CO level inside the house to be 0 ppm
    Checked CO level after heat exchanger to be 0 ppm
    Validated furnace installation angle

    I speculate that either the heat exchanger is cracked or the combustion chamber is not properly sealed.
    How do I prove to the HVAC technician that this is the problem, or is there another problem that I have not yet discovered?

  2. #2
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    Apparently the tech didn't do a Combustion Analysis. Checking the CO pre and post heat exchanger won't till much. The CA will tell you what the furnace is producing and give a good idea if the HX is sealed or not. It is possible that the fumes are seeping back into the house which can be hard to track down.

    Has the tech smelled the odor you are complaining about or been in the house long enough to get the itchy eyes, etc.

  3. #3
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    Thread Starter
    Quote Originally Posted by BNME8EZ View Post
    Apparently the tech didn't do a Combustion Analysis. Checking the CO pre and post heat exchanger won't till much. The CA will tell you what the furnace is producing and give a good idea if the HX is sealed or not. It is possible that the fumes are seeping back into the house which can be hard to track down.

    Has the tech smelled the odor you are complaining about or been in the house long enough to get the itchy eyes, etc.


    The HVAC tech returned, and visually inspected the heat exchanger and found no cracks. He also did a combustion analysis before and after the heat exchanger and found no CO or particulates. Everything seems to indicate that the furnace is functioning properly. But the smell persists, I am wondering if I should consider something else...

  4. #4
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    Could be a furnace condensate drain hose not trapped. Some have trap in blower compartment and could suck exhaust fumes into the house if cracked or plugs missing.

  5. #5
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    You don't do a Combustion Analysis before and after the heat exchanger, it is done in the vent/exhaust pipe and tells you how well the furnace is burning. He was probably just checking for Carbon Monoxide which you will never pick up 30PPM in 800+ CFM air flowing past. If he hasn't been trained in CA he probably would not know what the reading are telling him.

    You can't look at a flame and say it looks good so it is burning properly. A flame producing 500 ppm CO looks the same as one producing 25.

  6. #6
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    Post the combustion analysis findings.

    Or go to the link in my sig and find a tech who has specialized combustion analysis training instead of the guy you had out there with a tool he doesn't know how to use.
    *********
    https://www.hvac20.com/ High efficiency equipment alone does not provide home comfort and efficiency. HVAC2.0 is a process for finding the real needs of the house and the occupants. Offer the customer a menu of work to address their problems and give them a probability of success.

    Find contractors with specialized training in combustion analysis, residential system performance, air flow, and duct optimization https://www.myhomecomfort.org/


    Site member map HERE!

  7. #7
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    If you want to see "the look of terror", ask for a written statement that the tech has done "Due Diligence".
    If no "look", the Agent has just unknowingly committed The Company Principal to something he/she never foresaw: accountability.

    Sit back and watch the fireworks.

  8. #8
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    No update for 5 days. I hope the OP hasn’t succumbed to CO poisoning.
    *********
    https://www.hvac20.com/ High efficiency equipment alone does not provide home comfort and efficiency. HVAC2.0 is a process for finding the real needs of the house and the occupants. Offer the customer a menu of work to address their problems and give them a probability of success.

    Find contractors with specialized training in combustion analysis, residential system performance, air flow, and duct optimization https://www.myhomecomfort.org/


    Site member map HERE!

  9. #9
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    Infiltration from a negative pressure in the house? Attic fan stuck on in the winter? Etc.,

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