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Community and Q&A

Is 170 watts normal for compressor heat?

pbldsgn | Posted in Mechanicals on

Just put a Mitsubishi MUZ-GE24NA in my home. I checked the standby loss with the inside unit turned off and found that it was drawing 170 watts. I called Mitsubishi and they said it is the compressor heater and it is always on any time it is below 66 degrees.

Needless to say I’m very unhappy to have put in something in that will use around $15 dollars a month before it even produces heat.

Has anybody else had issues like this or do I have a defective unit?

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  1. Expert Member
    Dana Dorsett | | #1

    I'm surprised that they turn it on at such a high temp- I'd always thought that compressor heat only needed to come on for startup when the temps were well below freezing(?).

  2. GBA Editor
    Martin Holladay | | #2

    I agree that it seems unlikely that this type of heater would come on at an outdoor temperature of 66 degrees. I'd be inclined to call Mitsubishi back and try to talk to a few engineers to confirm the information you were given.

    Note that measuring the standby electrical use of a minisplit unit can be complicated because of the power factor issue. For more information, you might want to read an earlier thread: Disappointing phantom load on 27.2 SEER Fujitsu 9RLS2 minisplit.

  3. pbldsgn | | #3

    I believe the measurement is correct, I am including a photo of how I checked it. the meter read .89 amps in this photo but is normally around .84 amps. I'll follow up with Mitsubishi.

  4. Aaron Birkland | | #4

    Did you see Martin's comment about power factor? You'd need to verify that you're calculating real power (measured in watts, W) instead of apparent power (measured in volt-amps, VA). Without correction, simply measuring the current and multiplying voltage will result in apparent VA, not real W.. I don't see anything in that image that suggests that the meter is doing any sort of correction for power factor. Can you confirm that your are actually calculating real power draw?

    The link martin posted about the phantom load notes that these units have very low power factor at idle, so VA will be high, but W will be low (VA * PF = W). Unless you're commercial, real power is the only significant value that affects billing.

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