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  1. #1
    Join Date
    Jan 2020
    Posts
    1
    Post Likes

    Air to Air Heat Pump in cold temperatures

    I live in South Dakota and currently, it is 11 degrees. I recently had to completely rebuild my home. I used Spray Foam insulation and have an Air to Air Heat Pump with electric backup.

    Prior to the rebuild, the heat pump could not keep up with the cold temps so Auxiliary Heat always kicked in when it was this cold. Now, the auxiliary heat only kicks in during the defrost cycle. The heat pump is providing enough heat to keep the house at temperature.

    My question is efficiency. If I switch to emergency heat, the air handler runs for a short time to heat the house perhaps 5 minutes). When on normal heating, the heat pump runs and heats the house but it runs for about 3 times the time to heat the house and the compressor goes on and off several times during the heat cycle. During normal use, the compressor draws about 4 KVA. Emergency heat draws about 15 KVA.

    Would it be more economical to continue to run the Heat Pump for 15 minutes verses running the Emergency heat for 5 minutes? Another factor that can't be measured is wear and tear an the heat pump.

  2. #2
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    4,434
    Post Likes
    Run the heat pump.
    UA Local 32 retired as of Jan 2020

  3. #3
    Join Date
    Aug 2008
    Location
    Hibbing, MN
    Posts
    828
    Post Likes
    Up here, in Northern MINNESOTA it is common to have a heat pump and a gas furnace. The tipping point with gas is about 20 degrees. At that temp, the gas furnace takes over for less cost than the heat pump.

    If my math is right, you pay for 15KVA for 5 minutes on electric heat, and 12KVA (4 X 3j for the heat pump. Sounds like running the heat pump is the way to go. If it gets much colder, you might need to reassess.
    If God didn't want us to eat animals... He wouldn't have made them out of MEAT.

  4. #4
    Join Date
    Feb 2009
    Location
    Home Energy Products: 170 DW Hwy, Belmont, NH 03220
    Posts
    56
    Post Likes
    What do you have for a heat pump. Wondering the efficiency rating.

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