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Thread: Attic to humid?

  1. #1
    Join Date
    Jan 2005
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    Going on a call today. HO said the other company told her she needed an attic vent fan. The pan,from what I'm told,overflows at least once a week on humid days and trips the float switch. Have any of you guys heard of the attic being to humid and producing this situation? I haven't. Then the other company told her to pour bleach down the drain,put a dehumidifier in the attic. I'm going to check the drain line,told it was a long run. Double trapped maybe?

  2. #2
    Join Date
    Jun 2005
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    Sounds like multiple problems depending on source of water.
    1. drain pan should drain on its own... checking drain line is good idea. Hope this is it and source of water is normal condensate backing up.

    If source of water is condensation on air handler or ducts:
    2. If insulation on air handler or ducts is insufficient to prevent condensation based on temperature and humidity levels (dew point) in attic, you have to control one or more of the parameters to stop the sweating.

    You can control:
    1. attic humidity
    2. attic temp.
    above two are tricky.... dehumidifier in the attic that is power vented in high humidity is a waste of time. Adding power vent if outside humidity is not too bad may work, depending on geographic area.

    3. insulation on air handler and ducts
    4. air temp in air handler and ducts (increasing cfms lower temp differential, increasing temp in ducts, but reduces dehumidification capability.

    I am in the middle of a more serious situation and, living in a high temp and humidity area have decided to seal the attic with closed cell foam to control the temp and humidity. I am hoping that solves my sweating duct problem, which began the day after we installed two new high efficiency SEER 18 heat pumps. If not, I will have to add supplemental dehumidification.

    Let's hope it is just backing up condensate. Hope it is not more complicated than that.

    This problem solving ain't cheap.

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