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Mitsubishi phantom loads

I have a Mitsubishi hyperheat multi split heat pump.  I have power metering on the HP’s branch circuit and the unit is always pulling around 220W. It used to go down to near zero, but doesn’t anymore.

 I thought it might be the crank case heater, but Mitsubishi says that should only pull 50W, and also should be turning off when the outdoor temp is higher.  This is a constant load. 

I've checked the indoor units (which are powered from the outdoor unit) and they are only pulling about 15W each.  I’d expect some off-operational load, but this just seems too high.  It accounts for 35-45% of our total energy use.

we’ve had the installer out, but they didn’t even bring the right communication cable, so I doubt their ability.


  • Jamie Hall
    Jamie Hall Member Posts: 18,953
    Have you electrically disconnected the Mitsubishi itself to make sure that it really is the culprit?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ratio
    ratio Member Posts: 3,180
    Yeah, chasing things like that you'll need to check the zero & calibration of your instruments, particularly if it's some comsumer-grade thing like a kill-a-watt.

    What are you using?

  • Larry Weingarten
    Larry Weingarten Member Posts: 2,549
    Hi, @Polycarp , Do you, or a friend have a thermal camera, like a Flir One? It's a very useful gadget! Use it to have a look at the equipment and see if you can find any hot-spots. That would tell you what's using the power, which will help a lot in troubleshooting.

    Yours, Larry
    JUGHNE Member Posts: 9,765
    edited July 2021
    Do you have an outlet near the outdoor unit?
    Is anything plugged into it?

    Code requires an outlet within 25' of AC unit, I have done the outlet with the AC circuit and using 12-3 cable to get the neutral there.

    The load of an outlet connected in this manner goes thru the AC CB.

    What type of measuring device are you using and where is it connected?

    Note: do you get the same reading if the system is in cool or heat mode?
    Perhaps there is a holding coil on the reversing valve drawing power when in the opposite mode of operation.
  • Polycarp
    Polycarp Member Posts: 135

    The metering system is Emporia. I double-checked with a fluke current meter and got the same answer +/- 1%.


    There is nothing else on this circuit but the heat pump. The outlet for the HP does not have a receptacle, so there is no way to plug something else in.

    I also get the same results whether the thermostats are in auto, heat, cool or off modes.


    I don't have a Flir or easy access to one, but maybe this is the excuse I've been waiting for. ;)
  • GW
    GW Member Posts: 4,542
    You have all the indoor units off when you are  getting 220w? What is Mitsubishi saying you should be reading? 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
    JUGHNE Member Posts: 9,765
    220 watts is a lot of heat, you could not hold a 200 watt bulb in your hand very long.
    You might have a power supply board/transformer etc that is cooking itself.

    I got a handy FLIR camera for 350 and that might be 400 now, but it is a great toy.
    I can see my heating loops thru the concrete and where the dog was laying 5 minutes after he gets up.

    For instance on a 12' ceiling with diffusers from 2 systems you can tell which is heating, without a ladder.
    Also for finding failed open steam traps on rads.
  • Jamie Hall
    Jamie Hall Member Posts: 18,953
    Kind of what I'm getting at... 220 watts is a lot of heat, indeed, and it has to be going somewhere. One of those nasties about energy is that it has a way of winding up as heat, pretty much every time.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England