Results 1 to 6 of 6

Thread: 3-way tripping AFCI

  1. #1

    Default 3-way tripping AFCI

    Posted By: AGT

    New construction - Switch "A" is powered from AFCI-protected circuit 1 controls stairway light along with Switch "B" which is powered from AFCI-protected circuit 2. This works beautifully. Switch "B" shares a box with Switch "C" and has one hot traveller on 12-3 W/G from circuit 1. All other hots on Switch "B" are off when circuit 2 is killed.
    Switch "C" is powered from AFCI-protected circuit 2 and controls the hallway lights along with Switch "D". This intermittantly trips the breaker. Sometimes, the breaker will trip on reset. Sometimes, the breaker will be fine until I start putting the wall plate back on. I've checked and double-checked the wiring, and all looks good, as do all connections. I don't think I have a shared neutral issue since everything in the box is circuit 2 except for the one traveller. I am at a loss to figure out why the breaker is now tripping.
    In both cases, the light is the intermediary, and the 2-ways are on either end of the circuits.
    Thanks in advance for any help.

  2. #2
    Join Date
    Feb 2012
    Location
    Kent, WA
    Posts
    242

    Default

    This doesn't make sense. Are all of these switches 3 ways? If so, how can switches A and B, which I think power the stair light, get power from 2 sources? A 3 way should be powered from 1 circuit and have 2 hot travelers. You also need to make sure the neutral in the 12-3 between switch A and B does not touch a neutral from switch C. I think a picture of what you have would be helpful, or more clearly identify what is on each terminal of each switch. Are switches A and D each in a box by themself?

  3. #3

    Default

    Posted By: AGT

    Sorry for the confusion. Both switches "B" and "C" are the secondary 3-ways - Switches "A" (circuit 1) and "D" (circuit 2) have the 12-2 hot wires to the common terminals, neutrals wired together, and grounds pigtailed to the switch. They have 12-3 travelers and grounds which go to their respective lights. From the lights, there are 12-3 wires going to switches "B" and "C" (white adorned with magic marker stripes and red are the travelers, black to the common, and ground). I've isolated both switches with their respective circuits in the box that holds "B" and "C", and "C" still trips under load which leads me to believe there is a loose neutral or ground at some other point on circuit 2. I'll visually inspect and check the connections for the receptacles and other wall switches tomorrow. "D" is in it's own box, and "A" shares a box with another switch on circuit 1 and a separately wired switch on circuit 3 (GFCI), so there are no shared wires with circuit 3.

  4. #4
    Join Date
    Feb 2012
    Location
    Kent, WA
    Posts
    242

    Default

    OK, makes sense now. You can trip an arc fault breaker if the neutral touches the ground under load (or a grounded metal box or cover or fixture part). If it trips when the light isn't commanded on, then it could be a traveler leaking to ground.

    One way to isolate the issue it to change the breaker to non-AFCI. If that breaker holds, it is the GFCI like portion of the AFCI that is tripping (i.e. a small current leak from hot or neutral that isn't going back through the breaker). If a non-GFCI trips, you have a major short to something. Could be a defective switch since you grounded it, or a pinched cable in a metal box (usually pinched by an overly tightened cable clamp.

    So check the wires, and especially check for all connections in any metal boxes.

  5. #5

    Default

    Posted By: AGT

    Thanks, Mark. I had already put in a regular breaker, and it worked fine. I guess it's just a matter of taking the other wall plates off and checking everything. Fortunately, there are no metal boxes, but I do wonder about one of the fixture mounting bars possibly being the culprit. I've also heard that CF bulbs can cause problems with AFCI circuits, so maybe I should rule that out first.

  6. #6

    Default

    Posted By: AGT

    Again, thanks for the help. As they say, start at the basics! Found a neutral wire touching a fixture mounting bar. Problem solved!!!

Similar Threads

  1. Dryer Tripping Breaker - Appliance tip of the week...
    By jeff1 in forum Appliance Tip of the Week
    Replies: 0
    Last Post: 07-09-2016, 11:24 PM
  2. Microwave surface light keeps tripping circuit
    By Elaine in forum Appliance Repair
    Replies: 3
    Last Post: 06-16-2015, 09:20 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •