# Is 170 watts normal for compressor heat?

Posted Tue, 04/08/2014 - 15:07
Edited Wed, 04/09/2014 - 12:05

Tags:

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(?).

Posted Tue, 04/08/2014 - 15:11

2.

Paul,
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.

Posted Wed, 04/09/2014 - 05:45

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.

Posted Wed, 04/09/2014 - 08:22
Edited Wed, 04/09/2014 - 08:28.

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.

Posted Wed, 04/09/2014 - 11:19

## Other Questions in Mechanicals

In General questions | Asked by Guillaume Dumont | Sep 1, 14
In Green building techniques | Asked by Silas Hoeppner | Sep 1, 14
In Mechanicals | Asked by Terry Lee | Sep 1, 14
In Green building techniques | Asked by Bruce Howe | Sep 1, 14
In General questions | Asked by Jeff Watson | Jul 12, 14