What is the problem with my GFCI outlet?

[Wade Lippman]

I live in a rural area and we get frequent outages of a second or less. I have one GFCI outlet that trips about half the time there is an outage. It has never tripped otherwise. Shutting the circuit breaker on and off doesn't trip it. The only time it trips in from outages.
I have 6 other GFCI outlets and they are fine. I replaced it once, but the new one does exactly the same thing.
There is nothing critical on the circuit, but it is annoying. Any idea why this is happening?

[Bruce Wrenn]

The problem could be a light fixture ballast. The one on front of shop trips every time there is a power flicker. Disconnected exterior light, and it doesn't trip. (Light wasn't turned on.) Same thing for upstairs bathroom in house. Had to relocate light to another circuit. Also if neutral and ground contact each other down stream from GFCI, it will trip. Spent the better part of a day searching this problem for a customer once.

[Jim Koepke]

I have one GFCI outlet that trips about half the time there is an outage. It has never tripped otherwise.

As Bruce mentioned, it may be caused by something connected to it. The GFCI in one of our bathrooms trips every time a certain night light is plugged into it. This is kind of odd since the night light has no ground pin or any other path for voltage to ground which is what usually trips a GFCI unit.

jtk

[Bill George]

The one in my shop close by my new plasma cutter which is NOT plugged into 120 volts but on its own 240 volt circuit now trips. Spike on the line or RF near will trip GFIs at times.

[Rich Engelhardt]

We had one circuit at one of our rentals that had only an outside outlet on it.
I tried everything - net GFCI, GFCI in the breaker panel. Noting worked.
I finally had someone in to pull all new wire. That solved the problem.

[Brian Runau]

I had a problem with one that a contractor wired, kitchen exhaust fan to. Brian

[Ken Combs]

As Bruce mentioned, it may be caused by something connected to it. The GFCI in one of our bathrooms trips every time a certain night light is plugged into it. This is kind of odd since the night light has no ground pin or any other path for voltage to ground which is what usually trips a GFCI unit.

jtk
GFCIs trip due to an imbalance in the current on the two wires. I think the threshold is around 4 to 6 milliamps. Meaning some current is leaking to ground, usually through a wiring fault or issue with a fixture. Some automatic lighting can cause a problem due to the tiny current that always passes through to drive the light sensor and may cause an imbalance during the transition from off to on. At least it appears that way to me in my unscientific testing. Old light ballasts also can cause this.

[Bill Dufour]

If it is outside or in a damp location moisture in the air can cause problems. I prefer to mount the GFCi indoors and daisy chain outlets outside.
BilLD

[Wade Lippman]

I understand it can be almost anything... but it only trips on power failures. What is it about power failures that can trip it? It doesn't trip when I turn the breaker off. What is the difference between a power failure and the breaker shut off?

A neighbor suggested that I disconnect various parts of the circuit and see how that affects the tripping; but since it only does it on half the power failures, testing it like that could take 10 years of having my circuit messed up.

[Bill Howatt]

Switching the breaker off and on is a relatively clean disconnect and reconnect. A power failure can possibly put a lot of spikes and other electrical noise with lots of harmonics on the line and the GFCI detects an imbalance. I think harmonics are a reason that GFCIs have trouble with electronic variable-frequency drives for lathes and other machines. The location of this GFCI from the panel may make it more susceptible than the others. Is it closer?
Try swapping with one the others you don't have trouble with?

[Curt Harms]

Switching the breaker off and on is a relatively clean disconnect and reconnect. A power failure can possibly put a lot of spikes and other electrical noise with lots of harmonics on the line and the GFCI detects an imbalance. I think harmonics are a reason that GFCIs have trouble with electronic variable-frequency drives for lathes and other machines. The location of this GFCI from the panel may make it more susceptible than the others. Is it closer?
Try swapping with one the others you don't have trouble with?

That seems like the most likely explanation to me. The fact that it only happens on power failure would seem to make other causes improbable. But then I'm no expert on these things.

[Jim Koepke]

I understand it can be almost anything... but it only trips on power failures. What is it about power failures that can trip it? It doesn't trip when I turn the breaker off. What is the difference between a power failure and the breaker shut off?

A neighbor suggested that I disconnect various parts of the circuit and see how that affects the tripping; but since it only does it on half the power failures, testing it like that could take 10 years of having my circuit messed up.

Can you make a list of the items on this particular circuit?

Thing like a capacitor start motor could be the culprit. A starting capacitor could be near failure or when starting it can cause a slight change to the current and voltage phase angles.

If you try the disconnect of various parts of the circuit, do half at a time. This way if the problem moves to a different breaker you will know the problem is in that half. Then break the problem part in half again.

That can be a pain though waiting for power outages to solve a problem.

jtk

[Bill Howatt]

My understanding is that when the power is restored after a failure, the GFCI trips even if nothing is switched on. If this is the case, then equipment connected but not switched on shouldn't have any effect.

[Jim Koepke]

My understanding is that when the power is restored after a failure, the GFCI trips even if nothing is switched on. If this is the case, then equipment connected but not switched on shouldn't have any effect.

I didn't get the nothing switched on feeling from the OP >
There is nothing critical on the circuit, but it is annoying. Any idea why this is happening?

Without knowing more about the situation, we are pretty much grasping at straws. There could be a pinched wire in one of the junction boxes with a slight path to ground when the power restoration causes a surge.

It may be similar to my case where a fancy night light causes the problem when power is restored.

It could be a power strip with a faulty surge protector.

Without more information, it is a guessing game.

At best, maybe suggestions toward different ways to trouble shoot the problem might lead to a solution.

One more thing, in my case the GFCI outlet is in one bathroom. It also has an outlet in the second bathroom and one outdoors that are down stream. When the weather comes in from a certain direction, it seems the outside outlet causes it to trip. Though that hasn't happened in maybe ten years.

There are a lot of possibilities.

jtk

[Lee Schierer]

If you have a dimmer or motion switch on the circuit, it may be the culprit.

[Bill Howatt]

I'll go along with more information required but this GFCI works just fine for periods of time when the devices are connected (normal circuit use) and turned on or not turned on. It also is happy with disconnecting the power by switching the breaker on and off and it only fails intermittently when the power is restored after a failure. If we are dealing with a problematic device on the circuit, I'd expect it to be failing frequently regardless of power failures.
The one device I would check out, mentioned by Jim Koepke, is a surge protector since it could do it's protection operation because of a large spike during a grid restore and this could drain some current to ground in the surge protector causing the GFCI to trip. A slightly complicating issue is that the surge protection may be inside some electrical equipment like a TV power supply, not just in obvious plug-in and power-bar protectors. So it would be prudent to disconnect everything if troubleshooting.

[Jim Koepke]

So it would be prudent to disconnect everything if troubleshooting.

One of the difficulties is this only happens (from the original post) when there is a power outage (for a few seconds) and happens about half the time.

A lot depends on the circumstances and could be related to how the power outage occurs. Some power companies have their own automatic circuit breakers. These can open and close during overloads when weather causes lines to cross or trees to touch a line. There could be two different line breakers in this circuit where one opens and closes cleanly and the other causes surges.

Like said before, there could be a lot of causes. This includes a GFCI outlet being more sensitive than others.

jtk