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  1. #1
    Join Date
    Mar 2007
    Location
    Melbourne Beach, FL
    Posts
    50

    Default mold growth on air supply register

    Every supply register has mildew that has reappeared after thorough :cleaning 6 months ago. Any ideal what is the cause.

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  2. #2
    Join Date
    Mar 2007
    Location
    Columbus GA
    Posts
    3,746

    Default Re: mold growth on air supply register

    Quote Originally Posted by Jack Wingo View Post
    Every supply register has mildew that has reappeared after thorough :cleaning 6 months ago. Any ideal what is the cause.
    Mold/ mildew will only grow where there is moisture.
    Moisture on the registers is likely from condensation.
    Check for:
    partially blocked/ clogged cooling coil
    Dirty air filter
    Crushed duct
    Oversized AC unit for this house
    Too much moisture in the air; cooking, showers
    Also hole in return duct

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  3. #3
    Join Date
    Feb 2008
    Location
    Caledon, Ontario
    Posts
    5,005

    Default Re: mold growth on air supply register


  4. #4
    Join Date
    Feb 2008
    Location
    Chicago IL
    Posts
    1,984

    Default Re: mold growth on air supply register

    I'm guessing you guys don't install humidifiers in FL? Or maybe there is one and its turned up too high.

    www.aic-chicago.com
    773/844-4AIC
    "The Code is not a ceiling to reach but a floor to work up from"

  5. #5
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,248

    Default Re: mold growth on air supply register

    Quote Originally Posted by Jack Wingo View Post
    Every supply register has mildew that has reappeared after thorough :cleaning 6 months ago. Any ideal what is the cause.
    Register and supply plenum box not sealed to drywall ceiling, this allows hot, moist attic air to leak through and condense on metal supply register.

    Quote Originally Posted by Markus Keller View Post
    I'm guessing you guys don't install humidifiers in FL? Or maybe there is one and its turned up too high.
    Markus,

    Humidifiers ... down here ... the only humidifier we use down here is called 'outdoor air', and we try to keep it turned as low as possible.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  6. #6
    Join Date
    Sep 2009
    Location
    Dallas, TX
    Posts
    24

    Default Re: mold growth on air supply register

    Mildew means moisture. These cases are a process of elimination. I'd start with the evaporator coil. Check the freon pressure (HVAC technician) but also check to see if the condenser is oversized. Short cycling condensers don't give the evaporator coil enough time to remove moisture from the conditioned air.


  7. #7
    Join Date
    Mar 2007
    Location
    Spring Hill (Nashville), TN
    Posts
    5,847

    Default Re: mold growth on air supply register

    I think Jerry has it right. I have also seen this in cases of poor housekeeping where the dust builds up and starts to grow.....

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  8. #8
    Join Date
    Dec 2009
    Location
    Corinth MS
    Posts
    14

    Default Re: mold growth on air supply register

    Don't forget to take a long good look at the evaporator condensate drain trap. Poorly designed or missing traps will let moisture enter the air steam causing the problem you have described.
    http://0323c7c.netsolhost.com/docs/T...aws%5B1%5D.pdf


  9. #9
    Join Date
    Apr 2009
    Location
    Melbourne, FL
    Posts
    180

    Default Re: mold growth on air supply register

    I agree with Robert; seen many cases where the homeowner has replaced the proper sized condenser with a larger one expecting better performance. What they get is a wet house and mildew buildup on the supply plenum. Actually had one homeowner boast that he had installed a 5 ton condenser at his 1500 Sg. Ft. home what I found was beads of condensation on the interior walls. Best to stick to the mfg. suggestions for sizing the condenser or heat pump.


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