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  1. #1
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    Aux elect heat cycles

    Have a Lennox x16 HP, var. speed, Harmony III system. Last night the outdoor temp was 27 deg. Based on the Led's on the Harmony board the aux elect. was bouncing between first and second stage.

    Question: Is it normal for aux heat to kick in while having 27 deg. outdoor temps?

  2. #2
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    It depends on many things.
    Its common on some systems. And others won't use aux until it gets even colder.
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  3. #3
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    Quote Originally Posted by jeepgrady View Post
    Have a Lennox x16 HP, var. speed, Harmony III system. Last night the outdoor temp was 27 deg.

    Based on the Led's on the Harmony board the aux elect. was bouncing between first and second stage.

    Question: Is it normal for aux heat to kick in while having 27 deg. outdoor temps?

    27'F range seems to be a common balance point.


    2 stage Heat Pump should be on 2nd stage for a while prior to aux heat.
    Your wording may need clarification.
    You may wish to lock out electric heat strips (aux heat) at > about 22'F,
    if you wish to conserve energy.

    How is the heat pump defrost operation in your area at < 30'F?
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  4. #4
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    Jan 2008
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    Lehighton, Pa.
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    With the Harmony board there is a four minute delay between all four stages if called for. Four stages meaning two for the HP and two for the back-up elect.

    There doesn't appear to be a lock-out function based on temperature for this unit.

    This unit handles the defrost function by using various sensors to determine when to activate the defrost. It is not like most units that are activated strictly using a timer. I don't necessarily have a problem with the strips running. I was just questioning if it should operate that way.

    Thanks for your response.

  5. #5
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    Your aux heaters could cycling on a bonnet sensor.
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  6. #6
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    Quote Originally Posted by dan sw fl View Post
    27'F range seems to be a common balance point.


    2 stage Heat Pump should be on 2nd stage for a while prior to aux heat.
    Your wording may need clarification.
    You may wish to lock out electric heat strips (aux heat) at > about 22'F,
    if you wish to conserve energy.

    How is the heat pump defrost operation in your area at < 30'F?
    on the coast of SC and NC heat pump defrost cycles are pretty often!! high humidity even in the so called "winter months" 27 degrees in this area is rare and you can and will see more AUX heat opreations, due to the higher defrost cycles and lower sized heat kits.
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  7. #7
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    Jan 2008
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    Lehighton, Pa.
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    Here's an update to my original question. Today, outside temp 48, stat set to 73. With one zone running, the unit ramps up to first stage aux. Another zone then calls for heat and unit ramps to second stage aux.

    The aux is 10 kw. Now, with the outside temp being 48 and the return air @ 73, shouldn't the heat pump be able to run without using aux?

  8. #8
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    If the stats aren't coming out of set back, then yea, there's a problem.

    Are you using set back on the stats.
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  9. #9
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    On this system, the stats only control when the system goes on/off. All of the operations are controlled by the Harmmony board.

  10. #10
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    Then there is a real good chance, the Harmony isn't set up right, or wired up right.
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