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  1. #1
    Join Date
    Dec 2005
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    What opinions do you have on the temperature of which the air source heat pump will turn off, and the emergency backup heat will turn on? I hear all kinds, between 20-35 degrees. I have a Trane XL14I, with a Trane gas furnace for backup. It is currently set at 30. If needed... house is in northern Montana. Is brand new construction. I prefer the use of the heat pump, it is quiter than when the furnace fires up. Even at 30 degrees outside, the heat pump is not on all the time, and has no problem keeping my house at 71. Thanks in advance for all the input.


  2. #2
    Join Date
    Jun 2002
    Bemidji, Mn
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    I start @ 20, if the homeowner says its still putting enough heat out, lower it in 5 degrees... Right now its 0 out, my Mitsu Mini is putting out 80 degrees, just turned it off today. Slab heat is up
    You picked a fine time to leave me loose wheel...

  3. #3
    Join Date
    Oct 2004
    Tyler, TX
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    It will vary according to region, size of house & system.
    A heat pump is sized for the cooling requirements of the structure, so balance point in the south would be lower than that in the north.
    The system designer will have determined the optimum setpoint for the outdoor thermostat.

    Watch your heat pump. When it is running 24 hours a day, and still keeping the house warm, it has reached balance point. It can't keep up below that outdoor temp by itself.

    Then you will need auxillary heat, not emergency heat. That means both run at the same time, if your furnace is electric.

    If you have dual fuel (gas furnace + heat pump) the gas will run stand alone below the balance point. It will automatically swith over to gas only.

    A lower temp setting on the outdoor thermostat will save you money on your fuel bill for both types.

    Emergency heat is in the event your heat pump is broken.
    A better name for emergency heat would be "set it here while you wait for the tech to arrive and expect a higher electric bill".

    Do a search on this site for "balance point".

    Good luck.

    RSES Certificate Member Specialist

    Southwest Regional Association of RSES Secretary, 2017

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