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I have a Midea U-shaped window air conditioning unit in the kitchen, plugged into a common USA 120v GFCI-protected outlet in the kitchen. When installed last year the unit worked fine all summer. This season however, after turning it on for the first time today the GFCI outlet trips seemingly as soon as the compressor is about to turn on.

I have read that this can either be caused by the compressor (or some other part of the unit) shorting out and voltage flowing through the ground, or by the compressor being relatively new and high efficiency, using variable voltage to regulate the motor and causing some currant leakage to ground -- essentially these might just be nuisance trips. Reference

AC unit is less than 1 year old. GFCI Breaker is ~5 years old. Location is USA (North Carolina)

Questions are:

1. How do I determine if this is a legitimate fault or a nussance trip?

If this is a legitimate safety issue I of course want to address it, but the Air Conditioning unit was fine last year, so... I suspect nuisance trips. Also, the unit runs fine in "fan only" mode; it's specifically the compressor (appears to be) that trips the GFCI.

What equipment or troubleshooting would I need to determine if this is a legitimate fault?

2. What can be done if it's not a legitimate fault?

Doesn't code mandate a GFCI breaker in a kitchen? There is not an alternate location for the window AC unit. Would a newer GFCI help? What are the code-legal options available if this is just a nuisance trip?

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  • Get one of those cheaters that lets you plug a 3-prong appliance into a 2-prong socket. Then, measure amps between the ground tab on the cheater and the ground pin or screwof a socket. Or stick a resistor across it and measure voltage across it (making the resistor into an ammeter shunt). Now you can test current on the ground wire. Can't imagine why it would fail, you didn't leave it outside all winter, did you? Commented Mar 24, 2023 at 19:26
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    Thanks @Harper! You caught me 😂 yeah, due to a number of factors (including the units design as well as a lack of storage space) we wrapped the outside in plastic for the winter. Not ideal, I know! Need to move to a better house… but after letting the unit run for 30m off the GFCI it now runs fine back on the original GFCI… so maybe the compressor needed to be woken up 😅
    – Josh
    Commented Mar 25, 2023 at 0:42

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Since it worked last year, I think it is more likely that something is broken than that it is a design flaw. A few things you can try:

  • Plug it into a different GFCI - If it does not trip on a different GFCI then (a) your current GFCI is a little too sensitive and (b) replacing the current GFCI should solve the problem
  • Plug it into a non-GFCI receptacle - If it works fine then either this is a (hopefully) very minor ground fault or a major ground fault. The problem is that if it is a major ground fault then it is downright dangerous!

Is it possible that the ground fault isn't of any real significance, as is often stated regarding refrigerators? Yes, that is possible, and a refrigerator and an air conditioner are essentially the same thing technically speaking. However, there are a few differences:

  • A refrigerator nuisance trip can cause loss of significant food and (even worse) in an unknown trip situation result in undetected but dangerous food spoilage. An air conditioner nuisance trip does not have those concerns.
  • A refrigerator itself is normally dry and the active parts are sealed/covered. An air conditioner is much easier to touch near the active parts and typically has condensate pouring out of it somewhere.

As far as GFCI in kitchens, the primary requirement is at a counter (food prep area) or within 6 feet of a sink. If you have a receptacle not at a counter and not within 6 feet of a sink then, as I understand it, it does not need to be GFCI protected even though it happens to be in a kitchen.

In addition, I would highly recommend a dedicated circuit for an air conditioner, whether GFCI protected or not. An air conditioner can use a lot of power and, unlike a kitchen appliance (toaster, blender, etc.) you don't turn it on/off as you use it - you let it run automatically (thermostat) all day long. Arguably (though you may not win the argument) an air conditioner on a dedicated circuit with a single receptacle could be installed in a kitchen even where the same receptacle would otherwise be considered a "countertop receptacle" and subject to GFCI requirements. That is the argument often used for refrigerators. Of course, one other difference is that by any normal definition, you must have a refrigerator in a kitchen and nearly all residential refrigerators are plug/cord connected. On the other hand, many homes don't have air conditioning at all and many of the ones that do have air conditioning use a central unit (always hard-wired) or other hard-wired air conditioner.


Based on OP's update that it is working fine on GFCI after first running for 30 minutes on a regular receptacle, it sounds like something got wet when the unit was sitting between seasons. That caused a minor but real ground fault. After the compressor ran for a while the heat dried out the problem area and now it is OK.

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  • Thanks! Couldn't reach another GFCI without an extension cord; tried a non GFCI and it seemed OK. Doing more troubleshooting
    – Josh
    Commented Mar 24, 2023 at 20:35
  • Awesome -- after letting the unit run for ~30 minutes on a non-GFCI outlet, it now works as expected in the GFCI outlet.
    – Josh
    Commented Mar 24, 2023 at 21:49

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