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  1. #1
    Join Date
    Jun 2009
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    Albuquerque NM
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    Indoor coil condensate produced during heat pump defrost?

    Is any condensate produced by the indoor coil during a heat pump defrost cycle? A friend told me it could happen, but it seems like the time would be too short to produce much of anything.

  2. #2
    Join Date
    Apr 2011
    Location
    SE Washington
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    559
    highly unlikely that could happen, the defrost cycle is typically time limited, and when its cold, the relative humidity is usually low, at least not enough to condense that fast
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  3. #3
    Join Date
    Jul 2004
    Location
    Massachusetts
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    6,841
    After switching to AC mode during defrost, by the time the indoor coil got cold enough to begin condensing, the defrost cycle would, in all probability, be terminated and the unit shifted back to heating mode.

  4. #4
    Join Date
    Jun 2009
    Location
    Albuquerque NM
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    2,485
    Quote Originally Posted by skippedover View Post
    After switching to AC mode during defrost, by the time the indoor coil got cold enough to begin condensing, the defrost cycle would, in all probability, be terminated and the unit shifted back to heating mode.
    And, in the case of an upflow dual fuel system like mine it seems like even if the coil got a little wet, the heat from the furnace would evaporate any moisture off the coil right away.

    I guess it could be different in other configurations though.

  5. #5
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    Jan 2004
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    PA
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    68,752
    Heat pumps with a bypass humidifier could condensate a little.
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  6. #6
    Join Date
    Jun 2009
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    Albuquerque NM
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    Quote Originally Posted by beenthere View Post
    Heat pumps with a bypass humidifier could condensate a little.
    That's what I have, but it's dual-fuel in an upflow configuration. The bypass take-off is above the coil and the humidifier is on the return.

    I have the VisionPRO IAQ with DATS in the supply plenum, downstream from the coil. The system is set to humidify in "desert humidification" mode, so I believe the IAQ will shut off the humidifier if the supply air is too cold. But, the humdifier water panel is probably still wet for that amount of time.

    Indoor RH is only 30%, but if the humidifier is on I guess RH would be higher at the coil.

  7. #7
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    Jan 2004
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    PA
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    Probably less then 30 seconds that the coil is cold enough to condensate moisture.
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