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I've been reading around the net for about 20 minutes and came across a lot of talk about how the fridge should be on their own 15 or 20 Amp breaker and the defrost cycle can cause the interrupt in a GFCI causing it to flip

I have a 20 Amp GFCI receptacle on a 20A Breaker that also feeds 4 other 15A receptacles that have a load on the fridge, the oven and 3 other receptacles along the kitchen counter, My old fridge (one big door, freezer door on top) had no problems on the GFCI frosted good, made ice, defrosted, everything was fine, I got a new side by side fridge and every 24 hours or so the breaker is flipped.

If it didn't happen with my old one, why would it happen with my new one, I changed the GFCI thinking it was the loose wires or just an old receptacle, Nope. next day it flipped, so i tested and confirmed all of the others outlets were fine, no loss, no interruptions

isherwood
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2 Answers2

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It is common for the startup or shutdown of the refrigerator compressor motor to cause a GFCI to trip. The defrost cycle, though, is less likely to cause the issue, since the defrost heater is resistive rather than inductive.

The issue occurs randomly because the motor operates from alternating current. If the thermostat shuts the motor when the cycle is near zero voltage, there's no problem... but if the voltage is near peak (~1.4 * the RMS mains rating), then it is more likely to trip the protector.

The issue is so common that under the NEC, home refrigerators in the kitchen are not required to have a GFCI. However, for safety, you might want to use a GFCI, anyway.

  • To help prevent an existing GFCI from tripping, a snubber circuit (resistor and capacitor) and/or surge protector can be added to reduce current spikes. This may require some trial-and-error testing. Rough values for the snubber would be a 1 microfarad capacitor (250 volt rating or higher) in series with a 500 ohm (2 watt or greater) resistor, for a 10 microsecond, 20 amp spike. But check that the snubber itself does not trigger the GFCI.
  • Newer GFCI's are supposed to be less susceptible to false tripping. [At one time, high-current Class B GFCI's were made for wet locations, but are no longer acceptable.] You might buy a new GFCI if you're sure it can be returned if it trips from the motor transients.

It's a bit of a bind: go with safety, knowing that food might spoil if the device trips, or remove the GFCI, knowing there is a chance of electric shock if the ground to the device is lost.

DrMoishe Pippik
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  • I'm thinking there was a GFCI feeding that circuit because it's on the sink side, and the fridge dispenses water and the oven splatters grease, but I've come to the conclusion that it is the defrost and the compressor, because in the day it's open and shut constantly, but at night it ices up then kicks on defrost, and it only trips at night sometime –  Sep 21 '18 at 07:46
  • I'm just not sure if I should replace it with a normal 20A receptacle or if I should try a class B GFCI –  Sep 21 '18 at 07:49
  • No. A Class B GFCI is not a better GFCI. It is a GFCI with a weaker, less sensitive trip threshold. It is unable to provide life safety protection. That defeats the entire purpose of using it in a kitchen. They are used to protect facilities and equipment. – Harper - Reinstate Monica Sep 21 '18 at 11:11
  • As @Harper states, Class B was meant for a specific use, and, AFAIK, is no longer being made. It's *possible* a 20 Amp GFCI (with a T- shaped neutral slot) would be less likely to trigger, but newer 15 Amp models might also work. A snubber might help... a starting value would be 1 microfarad in series with 500 ohms. See https://www.daycounter.com/Calculators/Snubbers/Snubber-Design-Calculator.phtml – DrMoishe Pippik Sep 23 '18 at 00:32
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    15 and 20 amp GFCI'S have the same trip threshold ,~5ma, the equipment style were at 30-100ma depending on the type. – Ed Beal Oct 22 '18 at 15:21
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The fridge shouldn't be on GFCI in the first place

GFCI is designed to protect humans from

  • typically 2-prong ungrounded,
  • non-metallic-chassis
  • appliances where the electrical parts are anywhere near a place you can reach
  • where the appliance may get wet, including its electrical bits
  • where it, or you holding it, could get into water e.g. Sink
  • and where all this couls possibly add up to an electric shock

A refrigerator is none of these. It's a grounded all metal chassis that can't move, all the electrical gear is all in the very back at the bottom where you could not possibly reach it, it won't get wet and you won't drop it in the sink.

Compare to the Range, which definitely has no GFCI protection, and is probably even wired NEMA 10 with no ground at all, and with the range chassis bootlegged to Neutral, seriously? how can this be legal?

So yeah.

And in fact, there is no Code requirement whatsoever for GFCIs on fridges.

Use a non-GFCI supply, preferably a dedicated circuit

The fridge is probably tripping because it does have a ground fault. You can armwave, and call it some oh/so/complicated motor issue, but it sounds like semantics to me, at the end of the day currents are not equal. The motor isn't storing quintillions of electrons, heck the new cyclotron at Berkeley Lab couldn't store that many electrons. The electrons are being returned in real time, and we know it's via ground because that is the only reliable return. That's a ground fault by definition. Whatevs. The point is that for all the above list of reasons, we don't care that much if a fridge has a small ground fault.

It's not safer; "everything's safer with GFCI" is simply not true, again for the above bulleted reasons the fridge is vanishingly unlikely to bite you. You have more to fear from that NEMA 10 range. Seriously.

If able, give the fridge a dedicated circuit with a special 1-socket receptacle that plugs in behind the fridge, and don't look back. Otherwise rearrange so the fridge is non-GFCI, but you still have a risk since sharing a circuit still invites an overload trip causing food spoilage.

Food spoilage is dangerous too - you imagine that "oh, the chef will taste the food first" no. Food for children or senior citizens is typically served blind. I have watched aides serve my mother a bowl of cereal with curdled, way out of date milk. Again, you have to balance other safety factors with the "everything's safer with GFCI".

Harper - Reinstate Monica
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