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  1. #1
    Join Date
    Aug 2008
    Location
    Sugarloaf, PA
    Posts
    61

    "sewer" smell from the ductwork

    I have a customer complaining of a "sewer" smell coming from the ductwork. The smell only seems to be noticeable when the aux heat strip is on. The air handler is an older Trane unit with 10kw electric heat strip. There doesn't seem to be an odor when only Heat pump is engaged or when the fan is operated, only when the heat strip is on. The exterior of the ductwork seems to be OK when visually inspected. I haven't cut into it yet to check the interior. The odor seems more intense the longer the aux heat is on. Any ideas.

  2. #2
    Join Date
    Oct 2011
    Location
    Toronto
    Posts
    35
    The sewer smell is throwing me off, is it possible something is on the heat strip thats burning, is the duct lined with anything? ie acoustic insulation?

  3. #3
    Join Date
    Aug 2008
    Location
    Sugarloaf, PA
    Posts
    61
    No, just standard ductboard. The heat strip was visually inspected and looks and operates normally. The customer says "sewer" smell, I have been unable to smell it on two previous visits, however, an electrician said it made his eyes water.

  4. #4
    Join Date
    Sep 2012
    Location
    North Wales, PA
    Posts
    13
    I can't say I have ever heard of a sewer smell with ductboard but during a geothermal install everyone was getting sick prior to and during the removal of all ductboard in the residence as well as a smell that was not mold.

    Sent from my SPH-L710 using Tapatalk 2

  5. #5
    Join Date
    Jan 2008
    Location
    Texas
    Posts
    1,740
    Your drain line trap is dry and being in a negative state it is pulling sewer gases.

  6. #6
    Join Date
    Aug 2008
    Location
    Sugarloaf, PA
    Posts
    61
    One of my first thoughts also. But the drain line exits the building through the wall and terminates directly outside., so there is no connection to any type of sewer line.

  7. #7
    Join Date
    Jan 2008
    Location
    Texas
    Posts
    1,740
    Maybe a dead mouse in ducts.

  8. #8
    Join Date
    Nov 2007
    Location
    Texas
    Posts
    425
    Change the strips

  9. #9
    Join Date
    Aug 2008
    Location
    Sugarloaf, PA
    Posts
    61
    The mouse makes sense. I'll run a camera through the ductwork to check it out.

  10. #10
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,450
    Look up dirty sock syndrome. Sound exactly like what you have.

    I've been battling it for years in my climate. It's coming from the evap coil. They make special cleaners. I've had about 50/50 success with those. The best solution is just to change the coil.

    The smell comes from a bacteria that grows on the coil and you only smell it when swapping from heat to cool (or defrost).

  11. #11
    Join Date
    Mar 2011
    Location
    Galloway, Ohio
    Posts
    62
    Makes me wonder if the coil is growing something and only the more intense heat given off by the strips is cooking the nasty that is growing on the coil.

  12. #12
    Join Date
    Jan 2008
    Location
    Texas
    Posts
    1,740
    Most of the time the strips are downstream of the coil.

  13. #13
    Join Date
    Aug 2008
    Location
    Sugarloaf, PA
    Posts
    61
    Heard of it, but never ran into it. I thought it was more prevalent in the humid south, and more commonly associated with high eff. equipment. The unit is about 20 years old, so replacing just the coil is not practical. I just looked at a Youtube video of a guy who claims to have solved the problem with a Pine-Sol solution sprayed on the coil. The aux heat issue has me stumped though, the smell should be most noticeable at initial fan start-up, not after the kick-on of the aux heat strip. If it is the evaporator coil, the smell should also be present in cooling mode. The problem is its about 5*F outside, not a good time to switch to cooling mode.

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