I need help! Issue with GFCI breakers being tripped for no obvious reason.

[luvtheheat]

Hi, I have an issue with GFCI breakers being tripped for no obvious reason. I'm hoping someone has seen this before and has a solution or suggestions.

My main service comes from a transformer about 60 feet away, into a 200 Amp panel on the side of my house. I had that panel upgraded 15 years ago and there are several GFCI breakers in it, and they never trip.

I have a cable feeding a sub-panel (SP1) on the other end of the house for my AC. It's a 60 foot run of 3X 1-0 (hot/hot/neutral) and bare ground. All aluminum. Neutral is NOT bonded to ground at SP1.

For about 15 years the only load on that was a 40 Amp 240v AC unit. Note that the feed to the AC unit from that second is 2 hots and a ground (No neutral). That's worked fine for 15 years.

I added a detached garage this spring. I ran a 30 foot run of qty 4, 4 gauge stranded copper from SP1 to SP2 inside the detached garage. 2 hots, neutral, ground. 60 amp breaker in SP1 feeds SP2.

SP2 is grounded by both the ground coming from SP1 (and thus main panel in turn), as well as a UFER ground in concrete foundation at detached garage. Neutral is NOT bonded to ground at SP2.

In SP2, detached garage, I have two circuits feeding 12 or so 120V receptacles. I put qty 2, 20 amp GFCI breakers in the panel, one feeds 6 outlets the other the other 6. Breakers are new as of Jan 2023. I've triple checked that the neutrals for the LOAD are wired to the proper place on GFCI breaker, and the neutral pigtail from GFCI is bonded to the neutral bus bar.

Currently the ONLY load whatsoever is the garage door opener operating 2x per day. It is on it's own dedicated circuit in SP2. GFCI at the I've verified breaker is not tripped before or after using garage door opener. There is nothing plugged into any of the 12 receptacles on the GFCI circuits.

I am 99.99% sure it's all wired correctly with no "built in" ground faults, etc. I did the work all myself. I'm not a licensed electrician but I know to study/read/understand best practices before I jump in. I also know enough to realize I may have missed something...

The issue is, I will find one or the other of the GFCI breakers tripped every few days. One time it's on the first circuit of receptacles, next time it's on the other. Again, there is ZERO load on the 2 GFCI circuits; nothing is even plugged into any of the receptacles. After I reset the breakers, they never trip immediately. Could be one day, could be five days later.

What's odd is I also have another receptacle circuit that has a 2-pole 20 amp 120v/240v GFCI/AFCI breaker, that NEVER gets tripped. As with the others, no load whatsoever at this time.

I'm wondering if the fact that my AC unit on SP1 is running pretty much around the clock is causing some very small mismatch between the hots and neutrals inside SP2 and thus tripping the GFCI breakers in SP2.

Has anyone run into something like this?

Any suggestions?

Thanks in advance.

MAIN PANEL




SP1



SP2

 

[mm08822]

Nothing jumps out as wrong but hard to trace wires in these pics.

Make sure the hot and neutral pair for each circuit are not swapped between the gfci cbs.
Have the recepts on both circuits provided power to loads before (not just plugging a tester/vm)?

I seriously doubt the ac has anything to do with the gfcis, but make sure it has a solid ground path/connections from sp1 to condenser.

Worst case, buy 1 gfci cb and swap out. Or replace one with a std cb and add gfci recept to first recept on that ckt.

 

[luvtheheat]

Have the recepts on both circuits provided power to loads before (not just plugging a tester/vm)?

Yes, over time I've run a shop vac on both circuits without issues.

If it continues much longer and I can't figure out why, I think I'll replace the first receptacle in the chain to GFCI and daisy chain all the others, and change panel breaker to NON-GFCI.

 

[PCustoms]

Sp2 appears to be bonded.

 

[luvtheheat]

Sp2 appears to be bonded.

Meaning what? Neutral to Ground?

Definitely not Neutral to Ground. Show me where....

 

[PCustoms]

Meaning what? Neutral to Ground?

Definitely not Neutral to Ground. Show me where....

What's the green screw?

 

[mm08822]

Sp2 appears to be bonded.

I'm not familiar with GE panels, but I thought the right bar was a grd bar bonded to the enclosure. If there is a strap (running behind the vertical buss) connecting left blk to right blk, then the green screw has to go altogether. Then there would need to be a grd bar added and all grds moved to it along with the feeder ground conductor. (I also see what looks like provision for bonding the left vertical bar below the lugs - is this redundant to the one on the right?)

Edit: Did this panel have a jumper bar between left and right bars below the vertical buss and was removed?

Still not following how this would trip the gfci w/o a load plugged in downstream of gfci. The circuit neutral would have to contact the grd wire somewhere after gfci protection.

 

[BillK]

I would start by swapping the circuits on the two GFCI breakers on the lower left. That would eliminate the breaker itself as the cause. If the problem moves to the upper of the two breakers when you move the wires then you know it has something to do with the circuits.

 

[Sinatra]

Are any of the twelve outlets located outside or in an area where they could get wet. If so water could bet the issue. Get a multimeter that’s capable of reading high ohms, like megaohms. Take all three wires circuit wires off of each breaker and the ground bar. Unplug or disconnect everything on the two circuits so you don’t read any devices. Using the ohms scale take readings between each of the conductors and then each conductor and earth ground. There should be no connection at all between any of the six conductors or the six conductors and earth ground unless you ran metal conduit.

 

[PCustoms]

I'm not familiar with GE panels,

The only one I've been in is a trainwreck....

Idk, the green screw jumped at me, as on Square D you've got to pull that for a sub. My only other concrete suggestion would be verify the correct neutral for each circuit.

Now to my conjecture: my house was a wiring mess, and I ran sections of wiring at a time before I swapped the panel. Somehow, something was going on where running my weldor on 120v GFCI in the basement smoked a coffee grinder and an oscillating tower fan on 2 separate circuits upstairs. No idea wtf happened, but came upstairs and fan was toast (digital control). The next morning I realized the kitchen GFCI was tripped and the coffee grinder was smoked.

My assumption was some weird cross connection that I fixed when I finished pulling new wire. I bet the OP has something similar.

I also question if an errant siding nail may have hit a wire, but the odds of that occuring on 2 circuits seems low.

 

[FredWanaker]

are there any other GCFI protected items or receptables on the GCFI breaker circuits? GCFI and GCFI do not play well together. Example, I added a GCFI receptacle by the outside back door to replace a standard one. For years I had random times when the bathroom GCFI would trip, or the one outside would trip. In 2018 we made a spreadsheet of all the wiring in the house while I was having some upgrades done. When the house was built, it was custom to place an outdoor circuit on the only GCFI in the house - in the bathroom by the sink. Once I realized the two GCFI were on the same circuit, and went back to a standard receptacle outdoors, the problem ceased. Now I just have a label attached inside the cover that says "GCFI protected see bathroom GCFI."

That said, I did have AC supply wire failure on high load days. When I re-sided the house, I found a siding nail driven thru the AC compressor supply romex. On high demand days the wire would swell enough to short thru the nail. Lucky the house never burned down. Only 1 or 2 inches at the AC contactor would be damaged when it would happen so there was no clue the cause was a nail was thru the AC compressor supply line.

 

[AC-WC]

Can't give any real electrical advise but had a GFCI circuit fixed last Friday in a pole barn. 1st electrician said it was my security light had a short. He disconnected the power (didn't cap the wires or anything) to the light and then put a new GFCI in. I went to put a new light in and it didn't work because he disconnected the power unknown to me at the time. Called in different electrician and we double checked all my items. All good, confirmed good power to the building, then he started tracing the wire from the switch to the outlet and found a mouse nest and then the neutral wire chewed for 10". It was touching the ground and tripping the GFCI. In other words the 1st guy didn't earn his pay....2nd guy did.
Can you check for chewed wires or are they all covered?

 

[luvtheheat]

Thanks for all the responses. MM08822's response got me thinking more. Below is pic of my model box except mine has another set of equipment grounding terminals to right. (Where the blue line is.)

The green screw PCustoms pointed out bonds the Ground line in to the enclosure itself. Required.

My UFER in is connected to the 2nd set of grounding terminals, all other grounds are to the left of it. So, all grounds connection to the UFER ground are relying on the green screw for a good connection.

Thinking that relying on only the green screw for connecting main ground in and all circuit grounds to the UFER is risky, I just added a piece of bare copper (12g) from the main grounding terminals to the second set the UFER is coming in on. Redundant perhaps but certainly acceptable. (Not shown below.)

The 2 pics below may help.

Hopefully.....

Thanks again.

 

[BillK]

I will just add that the fact that you have one GFI breaker that is not giving you a problem most likely rules out an issue with the overall grounding scheme. Thats why I suggested swapping the wires on the two gfi's at the bottom left to see what happens.

 

[luvtheheat]

I will just add that the fact that you have one GFI breaker that is not giving you a problem most likely rules out an issue with the overall grounding scheme. Thats why I suggested swapping the wires on the two gfi's at the bottom left to see what happens.

I have 2 single pole GFCI that are the ones that are giving me trouble. Feeding the 12 outlets.

I have a combo GFCI/AFCI that is not giving me trouble. (County failed me on my final inspection and made me GFCI protect the 9 outlets I installed on my ceiling for lights. Combo GFCI/AFCI was all I could find at the time.)

I have a 2 pole GFCI that is not giving me trouble. Feeds a combo of 120 and 240 V outlets.

If this continues after my last tweak I'll start swapping circuits around.

Thanks

 

[ez-duzit]

...

MAIN PANEL

On the right grounds and neutrals are connected.

 

[PCustoms]

On the right grounds and neutrals are connected.

So?

It's his main panel

 

[luvtheheat]

On the right grounds and neutrals are connected.

Yes they are, on main panel only, although the pic I posted does not show that. Ground and neutral at main are connected by a strap at the bottom of the 40 slot main panel.

See also post 3 this thread: https://www.garagejournal.com/forum/threads/electrical-faqs.356460/

 

[exranger06]

Since these circuits have nothing plugged into them most of the time, I would disconnect these circuits to help locate the problem. I would disconnect the hot leg and neutral from the breaker, leave the neutral pigtail from the breaker to neutral bar connected, and turn the breaker on. Leave it like that for a few days and see if the breaker ever trips then. There would be absolutely no reason for the breaker to ever trip when it's disconnected like that. If it still trips, then it's definitely a bad breaker. Maybe disconnect/test only one circuit at a time so you still have some outlets functional in the meantime.
If the breaker never trips, then I would reconnect it, but go to the first outlet and disconnect all the downstream outlets. Turn the breaker on so it's only powering the first outlet and see if it ever trips. If it does, then there must be a problem with the wiring between the breaker and the first outlet. If it doesn't, then connect the next downstream outlet and disconnect the rest. Keep repeating the test until you find the problem section.

 

[wyliesdiesels]

Anything upstream(line side) of the GFCI breakers will NOT cause the breakers to trip. Only an issue on the load side of the breakers cause them to trip

Also improper neutral to ground bonding will not cause them to trip either