Ground Fault Problems New Custom Home

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indman

Member
Location
Pennsylvania
Occupation
Electrician
Hey there! Long time listener, first time caller.

Check the TLDR at the bottom if you would like to skip the backstory.

It began last winter, when I got to wire my boss's house. The rough in went seemingly fine, and before we knew it drywall was up!
We installed 4" and 6" Lithonia/Juno WF6 and WF4 wafer lights throughout the house. Siemens brand panels and disconnects. The service is set up as follows:

Service Drop > 320A Meter Base > Shed with 200A Panel and 200A Disconnect
200A Disconnect > Pipe to Main House > 200A Generac ATS > 200A Main Lug Panel
200A Main Lug Panel has (2) Subpanels and only (1) spare space.
Ground Rods at meter.

I did not design this service, and I was less than enthusiastic about installing it. I suggested an alternative to this, since the 200A panel in the shed area could easily be a 60A or less subpanel. I digress..

Temp power was fine, no major issues were noted other than the usual miss on cutting out several of my electrical boxes.
I started doing my trim out behind the painter and putting in the final circuit breakers (AFCI, GFCI, etc...)

Everything was seemingly fine until I installed the dual function AFCI/GFCI breaker for the bathroom light circuit. As soon as this was done, the problems were either detected, or began. The circuit would trip seemingly randomly. There was some correlation with the use of a DeWalt 60V Compound Saw that was plugged into another circuit, but not always. I worked on troubleshooting this as soon as I was able. I bounced around between this job and other jobs frequently, so I wasn't able to troubleshoot this problem continuously. One note, as well, was that the time between trips could be days. There were times I would try a fix, and the circuit would stay on the entire time I was there. This caused the troubleshooting to drag out as well.

I began by checking the wafer lights and making sure none of the wires were pinched or nicked during cut-in. I use the Klein romex strippers, so this is usually not an issue.
I then looked in all of the switch boxes, and made sure there was not any shared neutrals, nicked wires, etc. I did find some damaged wires from cut-out saws, and replaced them, but the problem continued.
I tried to remove parts of the circuit to see if it would not trip, and narrowed it down to the master bathroom area that would consistently trip it. Then I started to test each individual wire in the bathroom, checking for continuity and resistance. I didn't find any continuity or resistance between grounds, hots, or neutrals with all wires open.
If this weren't frustrating enough, during my trials I had to keep working on other parts of the house, and after I installed a dual-function breaker for the basement area, it began tripping randomly as well! They would not always trip at the same time. It was usually one or the other.
The dual-function Siemens breakers are also not very explicit with what the trip was for. Two lights on the trip meant either an Arc fault to ground or a ground fault. To figure out which one it was, we replaced the breakers with AFCI only, and put a GFCI outlet inline with the bathroom lights and on the basement lights we did the same.
The good news is that the AFCI breakers have not tripped once since we did this, but the GFCI outlets, which are brand new, will still trip. For a while, with the circuits and GFCI outlets separate like this, I was able to get only the basement lights to trip, not the master bath lights.
I bypassed the basement light GFI to see what would happen, and the master bath GFI now trips randomly.
We also called the local POCO and asked them to make sure all their connections were fine. They sent someone and we talked a bit. Their side checked out and he suggested it could be the old well pump.

My supervisor seems to have less of an idea than me, so I'm trying to figure out what is going on. We don't have much for testing equipment because we are a multi-trade company that doesn't do any "service" work... even though we kind of do sometimes.

Any help or insight would be greatly appreciated, and I'm happy to answer any questions that the above did not clarify. Thanks for your time.


TLDR

Very random tripping of GFI outlet inline on circuits with lights and receptacles. Have tried many things. Welcome to any fresh ideas.
 

mtnelect

HVAC & Electrical Contractor
Location
Southern California
Occupation
Contractor, C10 & C20 - Semi Retired
This is my favorite subject ... You definitely have crossed neutrals somewhere.
This not going to be fun ... All the neutrals from the main service / sub-panel and junction boxes to the end of the circuit, must be identified with the main / sub-panel circuit numbers. This will be the only way to solve your problem.

I am now preparing a code change for the NEC 2026, see attachment.
 

Attachments

  • NATIONAL ELECTRIC CODE #1.pdf
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ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
This is my favorite subject ... You definitely have crossed neutrals somewhere.
This not going to be fun ... All the neutrals from the main service / sub-panel and junction boxes to the end of the circuit, must be identified with the main / sub-panel circuit numbers. This will be the only way to solve your problem.

I am now preparing a code change for the NEC 2026, see attachment.
A crossed neutral on a branch circuit fed from a different panel is not going to affect the operation of a GFI recpt, nor would one on the line side of a GFI recept fed from the same panel.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Why do you have bath lights and basement lights on a GFCI? Unless you just want to use a DF breaker, there is no code to GFCI protect bath or basement lighting. Maybe you have the bath lights on with the receptacle?
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
....TLDR

Very random tripping of GFI outlet inline on circuits with lights and receptacles. Have tried many things. Welcome to any fresh ideas.
The fact that the problem stayed and followed the circuit to the GFI recept is good news. GFIs trip for a reason, unlike AFCIs which can trip for no reason. I would try wiring up an old fashioned 100W incandescent bulb in a pig tail socket at different points in the circuit. When it's a tough problem to troubleshoot putting a load on the circuit can make the problem less intermittent.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
In situations with infrequent GFCI tripping, for diagnostic purposes it might be helpful to apply small, incremental amounts of GF leakage with a resistor from hot to the EGC. For example, a 120KΩ resistor would leak 1mA, a 56KΩ would leak 2.2mA, etc. You could apply just enough leakage to make it trip and then back off a bit, so that the culprit that's causing the problem leakage could be more likely appear.
Now this wouldn't help if the tripping was caused by a ground fault that was on/off in nature, like a relatively large GF current that was happening intermittently. But then again, this scenario could be difficult to diagnose by other means as well.
 

indman

Member
Location
Pennsylvania
Occupation
Electrician
Why do you have bath lights and basement lights on a GFCI? Unless you just want to use a DF breaker, there is no code to GFCI protect bath or basement lighting. Maybe you have the bath lights on with the receptacle?
Bath has lights above the tub and shower. Basement is unfinished and has receptacles.

The fact that the problem stayed and followed the circuit to the GFI recept is good news. GFIs trip for a reason, unlike AFCIs which can trip for no reason. I would try wiring up an old fashioned 100W incandescent bulb in a pig tail socket at different points in the circuit. When it's a tough problem to troubleshoot putting a load on the circuit can make the problem less intermittent.
I've tried putting a space heater at different points on the circuit, but it holds and doesn't trip directly.

In situations with infrequent GFCI tripping, for diagnostic purposes it might be helpful to apply small, incremental amounts of GF leakage with a resistor from hot to the EGC. For example, a 120KΩ resistor would leak 1mA, a 56KΩ would leak 2.2mA, etc. You could apply just enough leakage to make it trip and then back off a bit, so that the culprit that's causing the problem leakage could be more likely appear.
Now this wouldn't help if the tripping was caused by a ground fault that was on/off in nature, like a relatively large GF current that was happening intermittently. But then again, this scenario could be difficult to diagnose by other means as well.
I can try that, I've put the saw that will trip the GFI directly onto the circuit before though and it hasn't tripped it, but then I will plug it into a completely different circuit and it will trip it randomly when it starts up. Other times the circuit will just trip without any saw, and then stop for a while.

This is my favorite subject ... You definitely have crossed neutrals somewhere.
This not going to be fun ... All the neutrals from the main service / sub-panel and junction boxes to the end of the circuit, must be identified with the main / sub-panel circuit numbers. This will be the only way to solve your problem.

I am now preparing a code change for the NEC 2026, see attachment.
I agree with ActionDave on this - the crossed neutral would give me a quicker trip than what I'm getting as well. Thanks for your reply though.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Bath has lights above the tub and shower. Basement is unfinished and has receptacles.
Unless the lights mfg instructions say to GFCI protect them, I don't see where they are required to be by Code.
Basement (unfinished) receptacles are the only thing requiring GFCI.
 

indman

Member
Location
Pennsylvania
Occupation
Electrician
Unless the lights mfg instructions say to GFCI protect them, I don't see where they are required to be by Code.
Basement (unfinished) receptacles are the only thing requiring GFCI.
Wow. I had assumed this was correct as I had always been made to do it. I never bothered to look into the code for it.. but now I see that it's mainly the rating of the fixture.. wow. Well that will solve THAT GFI tripping, now I'm just going to cross my fingers that it doesn't create an issue elsewhere in the house...

Thanks!
 

indman

Member
Location
Pennsylvania
Occupation
Electrician
Those lights may not require GFCI, but if they trip one, something isn't right.
I agree, but I don't know that it's the lights. The only part of the circuit that is on the GFI is (4) sconce lights, (3) WF4 lights, a Nutone fan, and a Nutone 110 Fan/light combo. I've checked all the wires, so the only thing I can think of is an overheating driver in one of the LEDs. The tripping was occuring before I even put the sconces in, so I don't think it's them..

Seems to be a more systemic problem than an isolated incident with this circuit.

I've also randomly had the kitchen lights circuit trip (which is also a dual-function AFCI/GFCI breaker) once. Never again, but it has happened once while I was there.

I have a theory that there is some piece of equipment running that is having a ground fault, but the system should not be affecting other branch circuits, it would find the easiest path to ground, right? So if that's not happening, maybe the grounding system isn't being effective?
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Current uses all paths back to the source, which is the utility transformer.
The grounding system is working. The GFCIs trip.
Inductive kickback can affect GFCI and AFCI. This occurs when an inductive load is switched off and it does not necessarily need to be on the same circuit. You would or should be able to find the cycling of those items as they are rather predicable. Intermittent is a real PIA, as you have discovered.
 

Electromatic

Senior Member
Location
Virginia
Occupation
Master Electrician
There have been instances of bath fans tripping a GFCI--even here in the forums. Ptonsparky's comment about inductive kickback made me recall that. I believe some tried alternate brands of GFCI. Others employed some kind of choke. You might try experimenting with the fans and see if there are results. It could be some shoddy windings in one of the motors.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
220602-1017 EDT

Any time you have an inductor carrying current you have energy stored in that inductor. If that inductor is switched by a mechanical switch, then that inductor will maintain the same current flow somewhere, usually as an arc at the switch contacts, until the stored energy is dissipated. No matter what the switch is the energy has to be dissipated. It is that with a mechanical switch it is usually at the mechanical contacts.

With an 8' fluorescent with a magnetic ballast and multiple random turn off times I can produce several thousand volt transient conditions.

Other inductive loads may produce comparable results.

An old automotive ignition system worked on this basis.

.
 

Amps

Electrical Contractor
Location
New Jersey
Occupation
Electrical, Security, Networks and Everything Else.
Unless the lights mfg instructions say to GFCI protect them, I don't see where they are required to be by Code.
Basement (unfinished) receptacles are the only thing requiring GFCI.
You don't want those lights going off when the GFI trips. Makes no sense.
 

Amps

Electrical Contractor
Location
New Jersey
Occupation
Electrical, Security, Networks and Everything Else.
Do you want them going off when an AFCI trips? Nope.
What if either are doing what they are designed for? Point being, if the GFCI is tripping, most likely there is a problem. It needs to be identified.
It it's not Code to have the lights on a GFI, then they shouldn't be on a GFI. Lights go out, someone gets injured in the dark.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Please cite the code section that precludes lighting circuits from being GFCI protected.
I think there was a typo and should have read "If it's not code............" Think he was saying that if it wasn't required then don't put it on lights. I don't put lights on GFCI but I'm not worried about someone getting injured in the dark. It would be no different than when the power goes out.
 
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