Troubleshooting AFCI nuisance trippings question

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subman

Member
Location
Monmouth County
I dont do much residential wiring since my backgound is mostly industrial wiring. My experience with AFCI breakers is limited so if the question seems stupid please excuse me. I recently wired several rooms in a home renovation.
Problem 1-When I energized the master bedroom lighting circuit (AFCI) the breaker tripped immediately. I started troubleshooting and isolated the lighting feed, no trip. Connected the HH, tripped (with blubs installed). Connected ceiling fan power feed ( no trip). In the old days, I would assume a dead short on the HH circuit. Now Im not so sure anymore with the reputation AFCI's have with nuisance trippings.

Problem 2-connected receptacle feed-plugged in cordless drill charger-tripped (AFCI). Isolated feed-no trip. Plugged in cordless drill charger into another AFCI circuit-no trip.

My question is how can you tell the differnce between nuisance trippings and short circuit trippings?
All the wiring, outlets and breakers are all new.

I plan to go back and replace the AFCI breakers with standard. (for testing purposes.) Any suggestions would be much appreciated. Thanks in advance.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
I, for one, need a little more information.

"HH" is, what? A high hat recessed fixture? What is the type of lamp (incandescent, CFL, LED, etc.)?

Multiwire branch circuit home run, or two 120 Volt branch circuits?

Which AFCI, make and model?
My question is how can you tell the differnce between nuisance trippings and short circuit trippings?
Your question, in my opinion, is the heart of the matter. The trip of an AFCI that comes from the signal processing that the device does can't be directly attributed to the AFCI electronics except for when the device has an indication that it reports. Some breakers report with a LED and blink codes. The manufacturer's instructions about troubleshooting are the only help.

Depending upon the make and model of the AFCI, the trouble shooter may also have to prove that there is no ground fault on the completed wiring, very similar to what is done with wiring protected by a simple GFCI. (The ground fault current, instead of 5 milliamps in the case of a GFCI, is somewhat higher in AFCI. OR, is not an issue at all, depending upon the particular make and model of AFCI.)

Otherwise, one is left with proving that the wiring is mechanically mistake and fault free in order to rule out "short circuit trippings".

Having proven the mechanical wiring is good, one is left with either a genuine event trip by the AFCI circuitry, or, something that is fooling the AFCI circuitry into tripping. . . the so-called "nuisance" trip.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
I, for one, need a little more information.

"HH" is, what? A high hat recessed fixture? What is the type of lamp (incandescent, CFL, LED, etc.)?

Multiwire branch circuit home run, or two 120 Volt branch circuits?

Which AFCI, make and model?

Your question, in my opinion, is the heart of the matter. The trip of an AFCI that comes from the signal processing that the device does can't be directly attributed to the AFCI electronics except for when the device has an indication that it reports. Some breakers report with a LED and blink codes. The manufacturer's instructions about troubleshooting are the only help.

Depending upon the make and model of the AFCI, the trouble shooter may also have to prove that there is no ground fault on the completed wiring, very similar to what is done with wiring protected by a simple GFCI. (The ground fault current, instead of 5 milliamps in the case of a GFCI, is somewhat higher in AFCI. OR, is not an issue at all, depending upon the particular make and model of AFCI.)

Otherwise, one is left with proving that the wiring is mechanically mistake and fault free in order to rule out "short circuit trippings".

Having proven the mechanical wiring is good, one is left with either a genuine event trip by the AFCI circuitry, or, something that is fooling the AFCI circuitry into tripping. . . the so-called "nuisance" trip.


That's a bit too simple.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Just some hints on things to look for especially since your afci trips immediately.

1) Check that no ground wires are close or touching neutrals in receptacle boxes.
2) Check to make sure light fixture screws haven't scorred into a fixture wire, or fixture pinching wires.( I have found from factory a neutral in paddle fan light kit pinched against housing and in a LED recessed light trim a wire pinched between driver and heat sink before.)
3) Make sure no neutrals from different circuits happen to be tied together in switch boxes.
4) Verify no loose connections.
5) If you have a megger check between conductors for ground faults/loose connections.
6) You may actually have either faulty equipment or devices inserting to much interference.
 

electricalist

Senior Member
Location
dallas tx
Just some hints on things to look for especially since your afci trips immediately.

1) Check that no ground wires are close or touching neutrals in receptacle boxes.
2) Check to make sure light fixture screws haven't scorred into a fixture wire, or fixture pinching wires.( I have found from factory a neutral in paddle fan light kit pinched against housing and in a LED recessed light trim a wire pinched between driver and heat sink before.)
3) Make sure no neutrals from different circuits happen to be tied together in switch boxes.
4) Verify no loose connections.
5) If you have a megger check between conductors for ground faults/loose connections.
6) You may actually have either faulty equipment or devices inserting to much interference.
Afci can be a pain. I find that isolating the circuit doesn't work as well as with a short.
Its usually as stated, the ground is laying on the neutral and a load will cause it to trip and or when you plug something in they touch , so you pull the plug out and it's ok again .
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Try switching the AFCI breaker with one that you know works perfectly. If you still have the problem then you know it's somewhere in the wiring. If you believe it might be a short circuit try switching out the AFCI with a regular breaker and see what happens. If it doesn't trip then you may have one of the problems that Al and Electricalist pointed out.
 

subman

Member
Location
Monmouth County
Update

Changed AFCI breaker with one that I know works-tripped. Replaced breaker with a standard breaker-no trip. Separated everything in the switch box, only connected feed from breaker to circuit for recessed lights-tripped. Isolated first recessed light from rest of circuit-tripped. Disconnected light from feed-no trip. Reconnect light feed, removed the blub-no trip. Found the same for the other lights. No bulbs no trip. Bulbs make the breaker trip. I'm stuck.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
I think the last time I saw a afci trip with what seems to be a bulb was a neutral wire pinched ever-so-close to making ground contact but not actually shorting and when the load was turned "on" it would trip afci. Because normally if a neutral is actually in contact with ground the afci would trip immediately regardless of load due to the gf protection installed in the afci breaker.

those pesky recess lights and their internal wires have been known to get caught up in the blank junction box cover, hung up on spring tabs or upper plate, kinked over and scraped from pulling on them. Just some more things to check which may mean removing the inner can housing from it housing support to get in and look things over without going into attic.

By the way, what type of bulbs are they?
 

ActionDave

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

Changed AFCI breaker with one that I know works-tripped. Replaced breaker with a standard breaker-no trip. Separated everything in the switch box, only connected feed from breaker to circuit for recessed lights-tripped. Isolated first recessed light from rest of circuit-tripped. Disconnected light from feed-no trip. Reconnect light feed, removed the blub-no trip. Found the same for the other lights. No bulbs no trip. Bulbs make the breaker trip. I'm stuck.
Put in a GFCI breaker, see if it trips. If it does you have more work to do. If it doesn't call the AFCI manufacture.

I'm not being trite. AFCI's trip because of wiring errors. They also trip for weird, unexplainable reasons. Subbing a GFCI breaker is the best way I know to eliminate wiring errors from the equation.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Something else just came to mind. I think I had a problem like your once also when one of the light bulbs ( if they are still incandescent/ halogen) that had a loose filament, still to the point it lit fine but was not physically clamped to its leads inside the bulb and was actually arcing. I have seen this too before when bulbs blow they can cause afci to trip.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Put in a GFCI breaker, see if it trips. If it does you have more work to do. If it doesn't call the AFCI manufacture.

I'm not being trite. AFCI's trip because of wiring errors. They also trip for weird, unexplainable reasons. Subbing a GFCI breaker is the best way I know to eliminate wiring errors from the equation.

GFCI will only detect Ground fault or G-N connections.
Will not detect Loose arcing connections.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
GFCI will only detect Ground fault or G-N connections.
Will not detect Loose arcing connections.
I have troubleshot too many AFCI nuisance trips. They trip all the time on anything other than an arc.

Just went to a house where a dyson vacuum tripped one. Put in a new AFCI and the problem was solved. Funny thing is when the vacuum was plugged into a different circuit, wired to an existing AFCI breaker, no trip.

AFCI's stink. I wasn't the first to say it. I disagreed with the AFCI haters at first, my own real world experience led me to the opinion I have now. AFCI's stink.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
I couldn't find but one picture but I think you can see well enough from it a fault I found while troubleshooting an AFCI.

The HO had other work going on and had someone "straighten" up some wiring in his attic. He then discovered that one of the bedrooms was not working due to the AFCI being tripped. So he assumed the person had done something to cause the tripping. I was called to check it after that.

I was able to walk through his attic and trace the homerun from the bedroom to the panel. So I knew the other work that had been done hadn't caused the tripping.

What I found was in a ceiling fan, the wires had been pinched by the mounting plate. The bare EGC had pierced the neutral. Not an arcing problem, just a fault between neutral and EGC. In this pic, I had already moved the EGC away from the neutral but you can see the place on the neutral where it was pierced. Hope you can see it well enough in the pic anyways.

 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
I couldn't find but one picture but I think you can see well enough from it a fault I found while troubleshooting an AFCI.

The HO had other work going on and had someone "straighten" up some wiring in his attic. He then discovered that one of the bedrooms was not working due to the AFCI being tripped. So he assumed the person had done something to cause the tripping. I was called to check it after that.

I was able to walk through his attic and trace the homerun from the bedroom to the panel. So I knew the other work that had been done hadn't caused the tripping.

What I found was in a ceiling fan, the wires had been pinched by the mounting plate. The bare EGC had pierced the neutral. Not an arcing problem, just a fault between neutral and EGC. In this pic, I had already moved the EGC away from the neutral but you can see the place on the neutral where it was pierced. Hope you can see it well enough in the pic anyways.


That is one that any old GFCI working would find.
I won't find the loose connection at a newly installed fixture.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Good picture Sierra,
See folks this is the stuff we need to be aware of. This is the kinda stuff thats gone un-noticed till the AFCI. Well actually GF protection which is inherent to the afci.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
The bulk of faults and wiring errors are caught by GFP. Same goes for nearly all arc faults. Had the NEC just required GFP things like this would be caught without nuisance tripping for UL listed devices. Countries outside of the US and Canada figured it out a long time ago.
 

subman

Member
Location
Monmouth County
I want to thank everyone who replied, especially Little Bill for his picture. My troubleshooting has lead me to the the conclusion that the problem must be at the first reccesed fixture, since I isloated it from the rest of fixtures and tested the feed to the light with it being connected, tripping the AFCI. Then I isolated that fixture from the feed with no tripping of the AFCI.

Unfortunitely for me, I have to do all the troubleshooting from the attic, since the ceilings are sheetrocked already. I wont be back until Tuesday. I will post an update of what I find for those still interested.

To answer and eariler relpy, the blubs I'm using are R20 flood light blubs.

Thanks again
 
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