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I have 2 bedrooms on a single breaker, and just yesterday, the breaker tripped. No devices are plugged into any outlets. Both rooms have ceiling fans (with lights). Both rooms have 3 wall switches. 1 for the ceil fan's fan, 1 for the ceiling fan's light, and 1 controls the bottom-half of one of the wall outlets. If all 3 switches in both rooms are off, I'm able to reset the breaker. In one bedroom (bedroom A), all of the outlets work fine (testing with a night-light). In the other bedroom (bedroom B), one of the outlets works, but if I plug the night-light into any of the other outlets (there are 3 others), the breaker trips. I have replaced these 3 outlets, but no change. I have also tested all outlets in both bedrooms with an outlet tester tool, and I get "correct" on all of them. In bedroom B, 2 of the 3 "suspect" outlets have 5 wires going into them (2 hot, 2 neutral and 1 ground); the 3rd "suspect" outlet just has 1 hot and 1 neutral (and 1 ground). If I completely remove/disconnect the 2 outlets in bedroom B that have the 5-wires, and just leave the wires dangling in open air, then Bedroom A is completely fine (ceiling fan and light included). In Bedroom B, the 3rd "suspect" outlet is off, and the other outlet (the one that always works) still works. The ceiling fan and light in bedroom B do not work; switching on bedroom B's switches does nothing; the breaker does not trip. With those 2 outlets in bedroom B completely removed, there's nothing I can do to cause the breaker to trip.

Another data point: with all the outlets connected/installed, in either room, attempting to turn on the ceiling fan or ceiling fan light cause a trip (so, plugging something into bedroom B's 3 "suspect" outlets is not the only way to cause the trip).

I've visually inspected the wires in bedroom B's 3 "suspect" outlets, and they all look okay; I don't see any rips/tears in the wire's insulation, so I don't think there's a short or ground fault.

So I'm completely baffled, and I want to make sure I've tried as much as I can before I commit to calling an electrician. What's strange is that nothing has "changed" in the past couple of days; I haven't nailed anything into any walls, and I have plugged anything out-of-the-ordinary into the outlets. The house was built in 2008, so "old" wiring shouldn't be an issue.

Thank you very much for your time. Any suggestions would be greatly appreciated.

  • How does one arrive at a situation where there are 4 hots and neutrals but only one ground? Every cable should have a ground with it. – isherwood Dec 29 '15 at 21:56
  • with a multi wire branch circuit code allows 2 hot’s 1 neutral and 1 ground they must be on adjacent breakers and Identified so they do not get split. This could be some version of that but there should be a ground with each pair. NEC 210.4.D – Ed Beal Dec 29 '15 at 22:44
  • is there a 3 way switch in one of the rooms?, if the wiring was not marked and a switch was replaced, or a fixture replaced. the hot could have been swaped – Ed Beal Dec 29 '15 at 22:51
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    It's an Arc-fault circuit interrupter (AFCI) breaker, so it could be detecting an arcing fault (which could be anywhere on the circuit, including hidden in a wall). – Tester101 Dec 30 '15 at 3:27
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    An Electrician should be able to find the problem a lot easier than a bunch of dolts on the internet. – Tester101 Dec 30 '15 at 3:28
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Just to close this question out, I followed the advice in the comments and did a stepwise disconnection of the various outlets and whatnot. This led me to suspect the ceiling fan in bedroom B. When I inspected its wiring, I noticed one of the ground wires was disconnected from the bundle it was tied-to (using one of hose colored plastic twisty things that look like a thimble). I fixed that and voila, problem solved! Thanks for all the comments and tips.

  • The term you're after is "wirenut" by the way :) (and you order them in beige or tan, not "hose colored" laughs ) – ThreePhaseEel Jan 6 '16 at 4:21
  • It's worth noting that an open ground should not cause a breaker to trip unless perhaps....... do you think it was so loose and so out of place that it was touching one of the black, hot wires? Or one of the white wires if the circuit has GFCI? I think it's worth analyzing further, because merely one disconnection in the ground path should not cause overcurrent, arcing, or ground fault, so something else wrong had to have been happening. – Billy C. Jan 6 '16 at 6:47
  • @ThreePhaseEel Ha ha. Meant "those colored." – Paul Evans Jan 7 '16 at 2:47
  • @BillyC. Funny you mention that - because the problem appeared again tonight! I looked at the wiring of both bedrooms' ceiling fans, and there were no loose wires (that I could tell). So I just tried tightening all of the wirenuts and that seems to have fixed the issue (for now). Thanks for the info - good to know about the open grounds. – Paul Evans Jan 7 '16 at 2:50
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You notice outlets typically have 2 backstabs and 2 screw terminals, one for each electrical side, and one top and bottom. That can be used one of two ways (but not both at once).

First, outlets can be "daisy chained". You plug hot and neutral from the supply into one set of pins, and use the other set to feed the next outlets downstream. Obviously, the outlet with only 1 hot is the end of the daisy chain - or it's the middle of the chain via "pigtailing".

Second, the duplex outlet can be split. You break off two interconnecting tabs. One hot and neutral feeds one outlet. The other feeds the other outlet. That's why one of your outlets still works - it's fed off the light switch. Of course, if you install an outlet in this position and fail to break off the tabs, it means you have bridged two separate circuits.

From a consumer's POV, there's no visual difference between a daisy chained outlet (2 hot 2 neutral) and a split outlet (2 hot usually 2 neutral). You could tell the difference with a voltmeter (in the latter case, both hots can be made hot).

Historically you could get away with jumbling up neutrals, because they all just went back to the same place: the neutral/ground bus in the service panel. (Mixing them up wasn't code, and it could overload neutrals and start fires, but it wouldn't trip any breakers.) That all changes with GFCI and AFCI. They work by comparing current flow on hot vs. neutral: did all the current that went out, come back? They should be the same: Any difference means current is exiting the circuit via some other path; a ground fault. So with GFCI or AFCI, the neutral must serve exactly the same outlets (or outlet halves) as the hot, or it will result in trips.

I suspect something is tangled up, possibly from original construction. Crossed neutral is the #1 mistake I've seen. Checking neutrals is a real pain.

So, pigtailing. You need to know about this technique, be sure to google it. Look in the back of each outlet box for evidence of it, it means the outlet is in the middle of the string despite not being daisychained. You'll surely see it at the split outlets, since you can't daisy-chain a split outlet. Pigtailing is the better technique, and you notice grounds are pigtailed.

  • A crossed neutral is an immediate trip, though -- not the "out of the blue" symptoms the OP is seeing. – ThreePhaseEel Dec 30 '15 at 23:22
  • A crossed neutral only trips if the outlet is used for something, good chance there are some outlets he's never used. Also perhaps in his testing and swapping, he crossed something else himself, particularly with those split outlet tabs. – Harper - Reinstate Monica Jan 5 '16 at 3:16

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