AFCI troubleshooting suggestions

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
You could have a neutral to EGC fault and it won't trip the breaker until a load is turned on. That's why it will trip on either side when something is turned on. If you put in a GFCI only breaker, it will do the same. Find where the fault is, or find where the neutral may be tied into another circuit.
That's good advice. I wasn't aware that that it wouldn't trip until the load is turned on but the more I tink about it the more it makes sense.. I spoke to the HO yesterday and will not be able to get there until wednesday. I hope I find it.
 

kwired

Electron manager
Location
NE Nebraska
That's good advice. I wasn't aware that that it wouldn't trip until the load is turned on but the more I tink about it the more it makes sense.. I spoke to the HO yesterday and will not be able to get there until wednesday. I hope I find it.
I believe as part of listing requirements class A GFCI's have a detection circuit to detect N-G faults even with no load on the circuit, a current is injected onto N and if circuit is completed via G- through the source and back to the GFCI on the hot, it sees same kind of imbalance that it is looking for in any trip condition.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
I believe as part of listing requirements class A GFCI's have a detection circuit to detect N-G faults even with no load on the circuit, a current is injected onto N and if circuit is completed via G- through the source and back to the GFCI on the hot, it sees same kind of imbalance that it is looking for in any trip condition.
I do not understand why the manufacturers didn’t do that with a AFCI’s as well. After all, a lot of the issues are caused by overdriven staples. Thanks for the info.
 

kwired

Electron manager
Location
NE Nebraska
I do not understand why the manufacturers didn’t do that with a AFCI’s as well. After all, a lot of the issues are caused by overdriven staples. Thanks for the info.
The dual function ones presumably do this. It is a ground fault protection thing and not an arc fault protection thing.

I don't think the GFPE devices do this either, just the class A GFCI's.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
The dual function ones presumably do this. It is a ground fault protection thing and not an arc fault protection thing.

I don't think the GFPE devices do this either, just the class A GFCI's.
I can't speak to other brands, but Eaton DF breakers do not trip from a neutral-ground fault, or crossed neutrals, until a load is applied. I just finished a new house that had a tripping DF breaker. I discovered it only tripped when the lights for that room was turned on. I found that the room had been mistakenly fed from two branch circuits and the neutrals were crossed. Lights turned on from either location of the two branch circuits would cause a trip.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The dual function ones presumably do this. It is a ground fault protection thing and not an arc fault protection thing.

I don't think the GFPE devices do this either, just the class A GFCI's.
Understood. Thanks for pointing that out.
 

mtnelect

HVAC Contractor
Location
Southern California
Occupation
Contractor
I can't speak to other brands, but Eaton DF breakers do not trip from a neutral-ground fault, or crossed neutrals, until a load is applied. I just finished a new house that had a tripping DF breaker. I discovered it only tripped when the lights for that room was turned on. I found that the room had been mistakenly fed from two branch circuits and the neutrals were crossed. Lights turned on from either location of the two branch circuits would cause a trip.

Would you support my proposed change to the NEC ?
 

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  • NATIONAL ELECTRIC CODE - Proposal NEC 2025.pdf
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goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Well, I found it and I first want to thank Action Dave and others who suggested that I use a GFCI breaker in place of a regular breaker. There was a dead short between the neutral and the EGC. I had to split apart all the wiring (blacks, whites and grounds) in (3) 3-gang switch JB's and a receptacle JB in order to trace the problem. On the affected circuit was the lighting in the 1st Fl bath, the hallway lighting, outdoor lighting, receptacles and lighting in the office. It ended up being in a 3-wire/3-way switch NM cable for the hallway lights. I wasn't able to isolate the problem at the recessed lights so I'm guessing it was a staple in the wire. I ended up cutting the EGC short at each end and installing a small wire nut on that EGC. I figured that was the best way to remedy this rather than cut the walls and ceilings open. This really threw me for a loop because the only time the AFCI tripped was when the bath fan was turned on or when the office lights were turned on. It never tripped when the hallway lights were turned on.

As luck would have it, an EC friend of mine called me while I was on this service call with another AFCI problem. He remodeled a portion of a kitchen and had to install an AFCI breaker for one of the circuits. He had installed that circuit in a 60A sub-panel. A carpenter was working in another area of the house where he plugged his saw into a receptacle fed off the main breaker panel. Each time he used his saw it tripped the AFCI breaker in the sub-panel. Any thoughts on this ? I don't care how weird you think they might be. I can believe anything at this point.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Well, I found it .... I ended up cutting the EGC short at each end and installing a small wire nut on that EGC. figured that was the best way to remedy this rather than cut the walls and ceilings open...
You still have potentially energized damaged conductors in that wall. They won't repair themselves.

Older saws are notorious for tripping AFCIs. They had universal motors with all sorts of sparking at the brushes.
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
. A carpenter was working in another area of the house where he plugged his saw into a receptacle fed off the main breaker panel. Each time he used his saw it tripped the AFCI breaker in the sub-panel. Any thoughts on this ? I don't care how weird you think they might be. I can believe anything at this point.
Had several time seen this, on GC installations. GC screaming over the *** AFCI that everytime they run the saw it would trip the AFCI.
Every time, I would find loose connections, either at the receptacle or the breaker. Tighten and no more tripping. Some so loose that I get a turn and a half of the screw to get torque. These guys don't have or use torque tools.
 

kwired

Electron manager
Location
NE Nebraska
I can't speak to other brands, but Eaton DF breakers do not trip from a neutral-ground fault, or crossed neutrals, until a load is applied. I just finished a new house that had a tripping DF breaker. I discovered it only tripped when the lights for that room was turned on. I found that the room had been mistakenly fed from two branch circuits and the neutrals were crossed. Lights turned on from either location of the two branch circuits would cause a trip.
Interesting, I thought it was a listing requirement for all class A GFCI's to have this neutral to ground fault detection provision, but maybe not.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
You still have potentially energized damaged conductors in that wall. They won't repair themselves.
Understood. At most it's 12' piece of NM cable going inside the wall and through the ceiling that has the EGC and neutral shorted together. What do you think is the worst that could happen ?
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The worst is that the pressure of the over driven staple hasn't quite broken through the hots insulation, yet.
If that should happen, HOPEFULLY it will trip the breaker. Then we'll have to talk with the HO about breaking open the ceiling and walls.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
If that should happen, HOPEFULLY it will trip the breaker. Then we'll have to talk with the HO about breaking open the ceiling and walls.
I wouldn't totally rule out an over driven staple, but I still lean towards a neutral to EGC fault. Have you taken everything on that circuit apart, including switches, lights, junction boxes, etc? You can verify the fault by disconnecting EVERYTHING and at the panel, take the EGC and neutral off the bar. Then check for continuity between the EGC and neutral.
 

growler

Senior Member
Location
Atlanta,GA
I wouldn't totally rule out an over driven staple, but I still lean towards a neutral to EGC fault.
Once upon a time I found a bad short ( neutral to ground) in a house that was less than 6 months old. Turned out to be a flying splice. It wasn't the electricians that did it. When they decided to finish the bonus room (before moveing in) they let the carpenters do the electrical.

As you say it could be an over driven staple but it could be almost anything. If you can learn who did the work that can give a clue as to what you may find.
 
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