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basic heat pump questions

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oreo123
oreo123 Member Posts: 72
in A-C, Heat Pumps & Refrigeration

Mini split heat pump is not used for heat in the winter (have a high efficiency nat gas boiler).

The heater in the outside unit, does that still run in cold temps if the heat pump is not being used?

If that heater is running on cold days its pushing the electric bill up. Would disconnecting the outside breaker for the unit damage anything? I think not but want to make sure. I would not want to risk putting a liquid slug into the compressor.

We are paying a high price per kilowatt in greater Boston. 37 cents per kilowatt (for generation, delivery, and other charges).

Thanks

Comments

  • Ironman
    Ironman Member Posts: 7,939

    It’s probably about 50 watts and temperature regulated. So turning the breaker off won’t produce any significant savings but may damage a compressor.

    Not recommended.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    GGross
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,651

    Agree with @Ironman

    The electricity used by the crankcase heater is miniscule.

    You could shut off the breaker to the outside unit in the winter. But you need to power it up at least 24 hours before running the unit. If you forget you may damage the compressor which will cost more than the electricity used………a lot more.

    mattmia2Ironman
  • winnie
    winnie Member Posts: 79

    I'd appreciate a deeper dive into the answer, because I use my minisplit in the same way, I use it for shoulder season heating and burn fuel for the coldest part of the winter.

    If I use the number of 50W and 75 days when I don't actually use the unit. That works out to about 90kWh and $27 worth of electricity. I have several separate single zone units, so that electricity use is bigger than miniscule but less than the cost of damaging the units.

    Would it be sufficient to wait a day between applying power to the unit (including the crankcase heater) and running the unit, or are there other issues with turning off the heater?

    Thanks

    Jonathan

  • pecmsg
    pecmsg Member Posts: 7,366
    edited 4:58PM

    $27 is cheap insurance

    But it’s your compressor!

    GGross
  • mattmia2
    mattmia2 Member Posts: 17,685
    https://forum.heatinghelp.com/discussion/comment/1900625#Comment_1900625

    your math is wrong. it has a t-stat, it only is on when the crankase is below a certain temp.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,651

    @mattmia2

    Most CCH are on all the time unless the compressor is running.

    @winnie

    24 hours is fine. Liquid refrigerant will migrate to the coldest part of the system when the compressor is off. This is usually the compressor as it is outdoors and the indoors is warmer in the winter. Since a compressor isn't supposed to pump liquid, the CCH keeps the compressor warm, so the liquid migrates elsewhere. 24 hours is the rule of thumb. It probably takes less time.

  • winnie
    winnie Member Posts: 79
    https://forum.heatinghelp.com/discussion/comment/1900631#Comment_1900631

    My math isn't far off, and I confirmed it by measurement.

    For purpose of this discussion, the minisplits are sitting unused on the coldest days; these are also the days that the t-stat would call for crankcase heating. I have an energy monitor that looks at the minisplit circuits. In January of 2026, on days when I wasn't using them for heating, each unit used about 1 kWh per day. I do see some lower usage days, but long stretches where the heater runs continuously.

    I am in Springfield, MA, so my data log is probably relevant to the OP.

    On the other side of the coin, looking at the energy use record I see that I actually did use the minisplits for heat on a few days during this time period. Given the current cost of oil I'll probably just leave the power on to the units and use them at lower temperatures then I've chosen in past years.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,651

    Some of the MINIs don't have a CCH but they send a small current through the compressor windings to do the same thing

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