Light switch tripping AFCI - Stumped

[adrnln8]

Hi All,

New to the forum, been doing a lot of research on the current problem we have and I'm not finding solutions so I've got to bug everyone with a new post. Thanks in advance for any help.

Doing a basement remodel/finish. Main Panel was too full to add the necessary breakers for the basement so we added a 70amp subpanel in a storage room of the basement. The basement will have a new bedroom so the owner has requested an AFCI breaker for that room. There are two light switches in the bedroom, one for the ceiling light and one for two Halo can lights above the head of the bed. Whenever the can lights are switched on, the AFCI trips. That switch is the last item on the circuit, furthest from the panel. So here's what I've done:

Initially the bedroom was on a regular 15amp breaker when we first powered up, everything worked fine, no issues. Then we installed the 15amp AFCI (correctly, I've checked 10 times) which turned on and held while we went to check receptacles and lights. Starting with the first switch from the panel, it was turned on and off successfully. Then testers were inserted into each of the three receptacles as we move down the circuit, those were all correct and fine. Then we came to the switch for the can lights - pop. Damn. So I checked the wiring from the switch to the lights, pulled all the connections out to make sure nothing was touching and tried again. Pop. Shoot damn, time to dig deeper. I took the second/last can light of the circuit, pop, took the first off and re-connected the second, pop, took them both off and flipped the switch - held. Now I'm confused. So what I did next is important and baffling - I rewired the lights, made sure nothing was touching and that everything was perfect and took the light bulbs out. I flipped the switch - held. Ok, so it doesn't like incandescent bulbs, well let's try, LED halogen and flourescent, pop pop pop. Ok, it's the damn can light fixtures, so I installed a keyless with a bulb at each location instead, pop. Took, the bulb out - held! Tried a brand new AFCI, same same same. Powered the switch leg through a nearby gfci and put in regular 15amp breaker - held. Hammer went flying across the room at this point, :rant: bought drywall guys some taquitos to fix the damage.

This is where I give up, advice please.

 

[GoldDigger]

1. Find out whether it is the AFCI or the GFI component in the breaker that is tripping! If the breaker has no diagnostic function replace it with a GFCI breaker to test.
2. Mist likely it is a ground fault since it does not happen with no bulbs in place.
Either the neutral is crossed to another branch circuit (maybe in the process of pulling a neutral to a switch box?).
Or maybe there is a pinched or nailed wire causing a neutral to ground connection somewhere in the run to the cans.
3. But you tried powering with a different GFCI branch. What was still different about the original wiring compared to how you repowered the switch leg?

Tapatalk!

 

[ActionDave]

The AFCI holds when there are no lamps in the circuit because there is no current flowing. Sure sounds like a neutral to ground fault somewhere in the circuit.

You said you plugged in a tester to the recpts, did you plug in something that would draw some current like a drop light or a drill?

 

[GoldDigger]

4. One more possibility if you have completely ruled out a ground fault issue. Maybe it is the snap switch itself which is generating a false parallel arc signature when closing.
Quick test for that is to unscrew bulbs, turn on switch and then screw in the bulbs one at at time. If the circuit holds until you turn switch off and back on, then look hard at it being a defective switch.

 

[ptonsparky]

The AFCI holds when there are no lamps in the circuit because there is no current flowing. Sure sounds like a neutral to ground fault somewhere in the circuit.

You said you plugged in a tester to the recpts, did you plug in something that would draw some current like a drop light or a drill?

Time for a megger. $$$

4. One more possibility if you have completely ruled out a ground fault issue. Maybe it is the snap switch itself which is generating a false parallel arc signature when closing.
Quick test for that is to unscrew bulbs, turn on switch and then screw in the bulbs one at at time. If the circuit holds until you turn switch off and back on, then look hard at it being a defective switch.

Time to try a different switch. Change brands. .$

 

[Dennis Alwon]

AFCI breakers need to see about 4 amps before it will detect an arc fault-- at least this is true for Ge- So the lights may show the cause of the arc but it may not necessarily be the cause. Had a situation where my guys were testing and thought it was the lights but it was the fans. The turned the fans on first and they were fine unless it was high speed. Medium speed the 2 fans held the breaker. Turned on hall lights and pop. The fan was the issue not the lights.

The small 4" Halo cans used to have a problem in the socket but if you bypassed the sockets then my guess is the problem is in an outlet somewhere.

 

[mopowr steve]

I have seen where an AFCI tripped when lights were turned on but found it to be a ground wire ever-so-close to a neutral in a receptacle box, something about adding the load of the lamps would trigger it. Also out of curiosity did you check to make sure the clamp in the can light junction box didn't actually cut into the NM. Can't remember what style of clamp HALO uses.
? Defective thermal cutout in can?
? Know how the interior round metal piece holding the socket at times pinches on the socket wires as they enter the housing could this be it maybe coincidentally tighten bulb - pinch wire, loosen bulb - unpinch wire?