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  1. #1
    Join Date
    Feb 2008
    Location
    Lucas, TX
    Posts
    107

    Which heat is run during heatpump defrost ?

    I've got the TH8320 honeywell tstat.

    Which heat is run, aux or emergency when the heat pump (Amana ASZ140361) begins its defrost cycle ?

    The tstat is setup as 3heat/2cool (though there isn't 2 cooling stages.)

    Thx.

    Adam

  2. #2
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    In nearly all systems, Aux heat and emergency heat are the same thing. In some bigger systems, the Aux heat may be staged, but again the same elements are used.

    paul

  3. #3
    Join Date
    Dec 2007
    Location
    Soudern Kaliphonistan
    Posts
    281
    and.....

    the defrost call comes from the control board, not the t-stat.

  4. #4
    Join Date
    Feb 2008
    Location
    Lucas, TX
    Posts
    107
    I see;

    So it depends on how the installer hooked it up.

    Thanks.

    Adam

  5. #5
    Join Date
    Jul 2008
    Location
    Dutchess County, NY
    Posts
    152
    usually the aux heat comes on while the HP is in defrost. when there is a call for defrost the HP automatically locks itself out, at that point the HP will put out a W2 signal... enabling aux heat..
    Last edited by Sonicview; 09-16-2008 at 07:40 PM. Reason: k

  6. #6
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by Sonicview View Post
    when there is a call for defrost the HP automatically locks itself out

    i think you need to re-evaluate that comment!



    .

  7. #7
    Join Date
    Jul 2008
    Location
    Dutchess County, NY
    Posts
    152
    Quote Originally Posted by Airmechanical View Post
    i think you need to re-evaluate that comment!



    .
    ok... technically speaking..it doesnt really "lockout". Defrost mode is identical to cooling mode except that the outdoor fan motor stops and auxilary heat is turned on to continue heating the house.
    Defrost is engaged by the defrost control board and utilizes a temp/timer control which includes a field adjustable time period between defrost cycles of 30 60 or 90 minutes...
    So , airmechanical is correct...it does continue to run but, it is just not heating the house, it is defrosting...but essentially the HP is "locked-out" from providing heat,... so, it enables auxilary heat until it has completed it's defrost cycle.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,337
    Since HPs and aux heat can be locked out.

    You shouldn't use term locked out to describe HP defrost operation.
    It will just confuse to many people.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by Sonicview View Post
    Defrost mode is identical to cooling mode except that the outdoor fan motor stops and auxilary heat is turned on to continue heating the house.
    you left out one part;

    what about the reversing valve!



    .

  10. #10
    Join Date
    Jul 2008
    Location
    Dutchess County, NY
    Posts
    152
    Quote Originally Posted by Airmechanical View Post
    you left out one part;

    what about the reversing valve!



    .


  11. #11
    Join Date
    Oct 2006
    Location
    The Beach
    Posts
    735

    Hmm Reversing Valve

    Surely we all know what the reversing valve does during the defrost cycle.
    Blue Fox

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