Don't understand this

[ote]

Went on a residential service call today about lights being out in a bedroom.This 2nd floor bedroom had french doors to a outdoor open deck with exterior wall fixtures adjacent to door. Went to panel and found tripped Arc fault breaker labeled master bedroom, and tried to reset but immediately tripped. Asked HO if they had installed anything new lately and they said they changed light bulbs in the exterior fixtures and noticed the socket was loose in one of them. I then looked at the fixture and removed it and reset the breaker and it held....Now the Question.... I was able to tighten the socket (stem nut under socket loose) and as I was reinstalling fixture with light switch in the OFF position with bulb out of fixture, I connected neutral first, then switch leg, and as soon as I tried to connect the ground wire (yea I know, been taught better about sequence of connections) the arc fault breaker tripped again. Don't understand why this happened with switch off, bulb out, or maybe I don't understand operation of Arc Fault breakers. Anyway, removed fixture and capped off wiring to be able to have lights in the bedroom..............any thoughts???????????

 

[JES2727]

Maybe a neutral to ground fault in the fixture? I'd replace the fixture.

 

[cadpoint]

With a circuit for a AFCI, no "Shared Neutrals" of another circuit; that's how they work.

Loose or improper wiring will be seen by it. pinched wires (touching), staples through multiwire wires, corrosion...

You isolated in front of the problem, the problem is down line meggar the whole circuit and work down line...

 

[Chamuit]

I had this happen on a job last week. I was installing cans and the AFCI kept tripping everytime the neutrals and grounds or hots touched. The switch leg had a dimmer on it. I'm guessing that there is a little leakage through the dimmer that the AFCI can sense.

 

[hurk27]

the shell of the socket is grounding out, as was said, even with the switch off to the light, if the neutral comes into contact with the grounding conductor or somthing that is grounded it will trip an AFCI, This will also happen on a GFCI protected circuit, switch off for a whirlpool, and a neutral to ground fault happens GFCI will still trip.