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advanced home DIY-er here. I put in a new Murray (Siemens) AFCI breaker and new 14-2 wire from the breaker box up straight to a light in a bathroom I'm remodeling (single wire for the complete run).

  • If I disconnect the load and neutral from the fixture (so they're hanging down, exposed), and turn on the breaker, all is fine. It stays powered up.

  • If put an LED bulb in a $2 plastic basement-style "outlet box lamp holder" and connect the load and neutral to it and throw on the breaker on again, it immediately trips the breaker. Neither the arc-fault or ground-fault LED indicators light up on the breaker. I believe this indicates an over-load protection, which seems odd for a 10w bulb.

so no load = no trip 10w bulb directly connected = trip

thoughts?

note: I pulled 3 other lines up with this one and they all work fine on the traditional breakers they're connected to. We did have blown-in insulation installed that meant guys drilling a million holes in the side of the house, potentially where that wire is. The likelyhood of partially damaging one wire (and not reporting it) but not severing it, or damaging any of the other circuits doesn't seem very high to me.

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    What happens if you try a different bulb? no bulb? What does this LED bulb do in another fixture?
    – Billy left SE for Codidact
    Commented Jan 5, 2016 at 4:28
  • It sounds like you have a breaker that is instantaneous tripping on excessive inrush current from the LED bulb. Can you put an amp-clamp (i.e. clamp-on ammeter) in "Peak Hold" on the hot wire to the bulb and then throw the breaker back on? That should give us an inrush current number to work with.
    – ThreePhaseEel
    Commented Jan 5, 2016 at 5:05
  • No bulb doesnt trip the breaker. Just tried a 40w incandescent bulb - it also trips the breaker. LED bulb works well in other fixtures. Also it appears that both of the LED indicators light up very briefly when the breaker trips. I must have missed this the first time since I thought they would have stayed lit. I believe this indicates "Arc fault to ground".
    – confuzzled
    Commented Jan 5, 2016 at 5:06
  • That is very strange. Can you change out the AFCI for a conventional breaker temporarily and try both loads? (I'm thinking that either the conventional trip or the backup electronic overcurrent trip on your AFCI is out of spec...)
    – ThreePhaseEel
    Commented Jan 5, 2016 at 5:09
  • I do have another traditional breaker I can use, but I'm reluctant to use it if theres a problem (basically, I don't want to burn my house down). I have another unused AFCI breaker in the panel and that trips the same way.
    – confuzzled
    Commented Jan 5, 2016 at 5:12

2 Answers 2

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Proper wiring

The first step, is to inspect the breaker installation. Make sure it's installed properly, and all connections are tight.

For an AFCI breaker, the grounded (neutral) and ungrounded (hot) circuit conductors should connect to their respective terminals on the breaker. The coiled grounded (neutral) wire from the breaker, should connect to the grounded (neutral) bar in the panel.

AFCI wiring

If the circuit neutral is connected directly to the neutral bar in the panel, the breaker will trip as soon as current is drawn through the circuit.

Short-circuit

Next you'll want to check the wiring for a short. Disconnect the ungrounded (hot), and grounded (neutral) conductors from the breaker. Use a multimeter to test continuity between the ungrounded (hot) and grounded (neutral) conductors, ungrounded (hot) and grounding conductors, and grounded (neutral) and grounding conductors. You should have no continuity between any of the wires (assuming there's no load connected).

Test the breaker

If you have a spare bit of cable left over, you could rig up an example test circuit. Connect a short bit of cable to the breaker, and wire the load at the other end. Carefully turn the breaker on, and see if the problem persists. If the breaker trips, try replacing the breaker (they are known to be/go bad from time to time). If the breaker holds, the problem is likely with the wiring.

Visual inspection

The last test would be to visually inspect the wiring, which I'm assuming is impossible (or quite difficult).

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  • @confuzzled When you install AFCI or GFCI breakers, the neutral pigtail from the breaker goes to the neutral bar in the panel. The circuit neutral goes to the neutral terminal on the breaker. In those photos, it looks like you have the circuit neutral and the breaker neutral going to the neutral bar. The correct wiring should look something like this.
    – Tester101
    Commented Jan 6, 2016 at 4:05
  • @confuzzled I've updated my answer.
    – Tester101
    Commented Jan 6, 2016 at 4:21
  • [Edit: I found the manual online and I believe the neutral wire is supposed to go to the breaker as well, but my father in law wired it to the neutral bus bar] As for the breaker: I'm assuming my much more experienced father in law installed it correctly, but maybe not. Should the pig tail from the AFCI breaker, the neutral and the ground wire be connected to the bus bar on the upper right? As is with test light: img.photobucket.com/albums/v201/turbo93impreza/… img.photobucket.com/albums/v201/turbo93impreza/…
    – confuzzled
    Commented Jan 6, 2016 at 4:27
  • looks like i was editing my comment as you were updating yours as well. i agree. i'll switch them tomorrow and let you know what happens. Thanks!
    – confuzzled
    Commented Jan 6, 2016 at 4:29
  • @confuzzled Did you get it working?
    – Tester101
    Commented Jan 8, 2016 at 0:40
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Sounds like a neutral to ground short. Maybe staple or from drilling. Inspect the contact with razor knife when removing outer insulation for cut wires inside switch box. It sounds like it's the home run and not the swith leg to the light.

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  • I bet it will hold closed end operate if you put the circuit on a non arc fault or gfci breaker. That will be the true test to see if i'm correct. Btw the neutral from Rolex goes to the arc fault terminal and the curly factory neutral goes to the neutral bar.
    – Bryan Kidwell
    Commented Dec 19, 2018 at 12:53

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