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  1. #1
    Join Date
    Feb 2013
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    Question Heat pump blows cold II

    My home has 2 zones each with its own heat pump. We have had all new duct work installed and the units cleaned last summer. before this and now when the heat is running periodically this smell will start coming out of all the vents, this happens for both units...cold air will also be coming out of the vents during this smell. I have researched the internet and many answers, all seemingly wrong, are out there. I have taken the top off both units, vacuumed all debris out(both units are outside, these have the blower units internal to them) and sprayed bleach water on the coils inside...let dry and re-assembled.
    directly after I am still getting this smell..the problem is, its not all the time and only few times a day, like the smell from your car ac after you have turned the car off then on again after a few hours.
    I am not sure the cycles of a heat pump, apparently it will blow some cold air after heating for some time...then smell.
    what is it?

  2. #2
    Join Date
    Jan 2004
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    Made this its own thread. You are not permitted to post in other peoples threads in the AOP forums, please read our site rules, thank you.
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  3. #3
    Join Date
    Mar 2009
    Mount Holly, NC
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    sounds like the electric strips are coming on as they are supposed to, when the heat demand is greater than the heat pump is capable of producing.
    the times of cold air during the smell times, are due to the heat pumps defrost cycle occasionally needing to melt the frost from the outdoor unit.
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  4. #4
    Join Date
    Aug 2004
    North Richland Hills, Texas
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    The musty smell and "cold" air blowing are likely happening when the system goes through a defrost cycle.

    Also, bleach is corrosive to every metal used in the system, never spray bleach water on/in any part of it...

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