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  1. #1
    Join Date
    Dec 2008
    Posts
    6

    Horrible smell coming from vents. Please Help !!

    I have a bad smell that intermittently coming from my vents when using the heat from my Trane heat pump system. The best way to describe the smell is a cross between urine/wet insulation and wet ash/burnt microwave popcorn. This is not a new unit however the house was renovated and new supply boxes and lines were added. Again it only occurs in heat and not in A/C mode, and is not consistent. Thought I had it narrowed to when the thermosat is raised to 70 or above, but last night it was set on 69 and got the smell and it was really bad. Went in the attic and removed the panel on the unit and can smell the smell inside. Not overwhelmingly, but definitely there. What I can see of what I believe to be copper coils have a little green on them. The insulation that is on the inside of the unit around the shell, for example on the panel door, looks to be pretty dirty and some what looks to be mild dust on the fan motor. Please advise. Thank

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,357
    Sounds like dirty sock syndrome. Getting the coil and inside of air handler cleaned might help, it might not. Sometimes the only solution is to replace the coil if cleaning can't get the odor to go away.

    During the renovation, was the system used for heating/cooling? If so, it possibly inhaled a good bit of drywall dust, which provides food for mold and other organisms. They thrive on the wet coils during cooling mode use, then die once the coil is no longer wet (between seasons or when unit goes into heat mode). The odor you smell is their remains being cooked by the hot coil.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #3
    Join Date
    Feb 2005
    Location
    cincinnati ohio
    Posts
    2,024

    smell

    You have a plumbing problem & the system is picking up the smell
    My avatar is a picture of a Goodman Silencer .....These were commonly used in Goodman country ....Photos by hvac tech ( PaysonHVAC )

  4. #4
    Join Date
    Dec 2008
    Posts
    6
    Quote Originally Posted by shophound View Post
    Sounds like dirty sock syndrome. Getting the coil and inside of air handler cleaned might help, it might not. Sometimes the only solution is to replace the coil if cleaning can't get the odor to go away.

    During the renovation, was the system used for heating/cooling? If so, it possibly inhaled a good bit of drywall dust, which provides food for mold and other organisms. They thrive on the wet coils during cooling mode use, then die once the coil is no longer wet (between seasons or when unit goes into heat mode). The odor you smell is their remains being cooked by the hot coil.
    The unit was used in heat mode during renovation. In response to the DSS is that the smell does not seem to fit the discreption of DSS from all that I read.

  5. #5
    Join Date
    Dec 2008
    Posts
    6
    Quote Originally Posted by bob hubbard View Post
    You have a plumbing problem & the system is picking up the smell
    Would that not require the system to be connected to the plumbing, ie the drain lines being tied to a plumbing line, which it is not? The drain pain lines are running out to the soffit.

  6. #6
    Quote Originally Posted by sgravely View Post
    Would that not require the system to be connected to the plumbing, ie the drain lines being tied to a plumbing line, which it is not? The drain pain lines are running out to the soffit.
    i think he may be talking about a leaking return picking up on a leaking plumbing vent?maybe not? anyway there could be a dead rat mad its way into your unit and got fried on the electric heat or something and is being cooked everytime it calls for emergency heat--have you or anyone opened the unit and did any inspecting?---thanks

  7. #7
    Join Date
    Dec 2008
    Posts
    6
    Stan,

    Yes, have opened the unit and no visual evidence of animal/rodent, dead or alive. Just dirty shell insulation and medium amount of dirt on the fan blades.

  8. #8
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,357
    Since you only smell it while the unit is in heat mode, it leads me to think you have a variation on DSS. You said it's a urine/wet insulation, wet ash/burnt popcorn smell. That does not sound like sewer gas to me (even with mention of urine, sewer gas is pungent and leans toward the feces side of the odor spectrum). With sewer gas you'd smell it in heating or cooling, or anytime the blower ran by itself.

    There's nothing to be lost by having your air handler professionally cleaned, and you may gain an end to the odor in addition to better performance from your system. Since you said it was used in heat mode during renovation, it still ingested construction dust and deposited same on the coil, air handler insulation, blower wheel, and blower motor. Your OP mentions a/c use, so that dust got wet at some point, providing two things microbes need to grow...moisture and food. You likely never smelled this odor until after the first cooling season following your renovation, when the heat was brought on again.

    As for why the intensity of the odor varied with the thermostat setting, the smell likely intensified whenever the auxiliary heat strips came on. When they're on, the level of heat output from the system is elevated. Odor intensity is directly tied to temperature. The warmer a stinky substance is, the worse it will smell.

    Get your system cleaned and then report if the odor is still there, or has gone away.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  9. #9
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    Another vote for DSS, the intermittent nature is due to it being tied to the defrost cycle, good way to test the theory, even if it wasnt present during the cooling season, try turning on the AC now and see if you get the smell, if so, it is for sure DSS

  10. #10
    Join Date
    Jan 2006
    Posts
    546
    The odor sounds like two things, some type of dirt on the evap coil thats trigger's the smell during defrost cycle or wet flex or ductboard.
    rick

  11. #11
    Join Date
    Dec 2008
    Posts
    6
    Ok, found out the culprit. After cleaning the coil and fan blades and vacuuming the handler insulation, I ran the system through several heating test. While viewing the handler with the panel off, I could see smoke coming from the 60 amp breaker on the side of the handler. Opened up the breaker box panel and the wire jacket was melting and the breaker frying to the point were when I went to unscrew the wire from the breaker, the screw assembly broke apart. Good news is that before I found the culprit, after cleaning the coil and fan, I did notice significant improvement on performance of the unit.

  12. #12
    Join Date
    Jan 2007
    Location
    N.E. Ok.
    Posts
    1,370
    I'm confident you will have a professional do the repairs as the melting of wire insulation is far worse than the smell.

    Quote Originally Posted by sgravely View Post
    Ok, found out the culprit. After cleaning the coil and fan blades and vacuuming the handler insulation, I ran the system through several heating test. While viewing the handler with the panel off, I could see smoke coming from the 60 amp breaker on the side of the handler. Opened up the breaker box panel and the wire jacket was melting and the breaker frying to the point were when I went to unscrew the wire from the breaker, the screw assembly broke apart. Good news is that before I found the culprit, after cleaning the coil and fan, I did notice significant improvement on performance of the unit.

  13. #13
    Join Date
    Dec 2008
    Posts
    6
    Yes, already have my electrician looking up the breaker info.
    Thanks.

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