We had a 20 Amp Double-Pole Type CH Breaker replaced with an arc fault breaker. This was done on several breakers, no issue at the time and only issues with one now.

I've since discovered that when lights are turned on in either of 2 attic spaces the breaker trips. I'm trying to decide what to check first.

Here's the setup: From an outlet a 12/2 comes up to the attic into a junction box. From there 12/2 power goes to: -1 switch that controls 2 lights (trips breaker) -a 2 gang switches in a different attic. The 2 switches control: a light in that attic (trips breaker) an outlet in the outside soffit (does NOT trip breaker with tester plugged in)

So, I'm thinking the wiring in junction box is fine (because the outlet is fine) and there's an issue with the switch or "lampholder" simple fixture in each of the 2 attic spaces. If so I'll start by taking apart each switch and fixture to make sure they are wired correctly, no bare wire is touching the box, etc.

Am I on the right track? Thanks!

  • The problem may be the lights themselves. What kind of light bulbs - incandescent, halogen, fluorescent, LED? If the lights are removable (e.g., Edison base) then try swapping for a different brand or type of bulb. Jul 18, 2018 at 14:20
  • Cree LED, same as the other 90 or so bulbs in my house. I first thought it was the bulb because it was damaged so I replaced with a brand new bulb, no change:(
    – user20127
    Jul 18, 2018 at 17:17

2 Answers 2


Arc Fault breakers detect -- wait for it -- arc faults. A connection is arcing. The #1 reason for that is use of backstab connections, but hold on - you're using #12 wire, and backstabs are not made to work with #12 wire. Well, if someone insisted, that might do it.

Regardless, 99% of wiring problems are at terminations, so that is the place to look.

  • 1
    I paid an electrician on the side: one was a standard porcelain socket, it looks fine but for whatever reason trips the breaker, a new one fixed that. He basically took out each thing (switch, light, etc) and wired without it to see what tripped it. The other must have been a loose connection, he pulled the switches, undid the wires, rewired the switch and it was fixed. Thanks!
    – user20127
    Jul 24, 2018 at 14:02

Arc faults do have problems with Flouresents & leds but not normally until 50% of the listing or above. Try putting in 2 old fashion incandescent bulbs if the problem is gone it is the Arc fault causing the problem, I have seen this quite often in the past, I have also found some cfl's that did not screw all the way in and could be arcing if this is the case the center conductor will normally be burned (I understand you are using LED's but some brands bay have the problem I have seen with some cop's) with the power off try lifting the center up and that would be a possible 2nd thing to check.

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