I’m pretty much finished helping a friend totally rewire a condo he bought and the inspector, at the final inspection, said that the bedrooms required AFCI breakers for the outlets.
There are two circuits for the bedrooms, and they are old and I simply left them in place. They are two hot wires (red and black) with a common neutral … the red and black are on separate buss bars so the potential between them is 240 volts. I can’t remember what this type of wiring is called, but my memory is that it is OK in the NEC.
When I hook up one of the hot wires to the first AFCI it works just fine. The second wire won’t work … if I remove the red wire from the break and attach the black the breaker trips immediately.
I suspect that the problem is that the neutral wires run through lots of boxes, some of which have other circuits, and that the neutral is tied to other neutrals.
That’s the history. My question is this. Is it really a requirement for AFCIs in a bedroom? If so, my suspicion is that I am going to have to trace the hot wires and the neutral all the way and separate any places where the neutral is tied to others. Since I’ll be doing that, my inclination is to run another neutral as well, so that these are two totally separate circuits.
Any advice or comment? I don’t think I can get a final until I either can show that this is not a requirement (hard to do, since the inspector is boss) or fix whatever problem there is in the wiring. Thanks ahead of time.
John
Replies
You're describing a shared neutral circuit. It's going to require a 2-pole ($$$) AFCI breaker.
I was thinking a traveler for light control at the outlet.
MMMm tools Put a meter on it.
Edited 11/13/2007 5:01 pm by ClaysWorld
I got to thinking Ya I know it's dangerious for and idiot. I know what it was used for ? a wall heater Maybe?
Edited 11/13/2007 5:47 pm by ClaysWorld
Ok last try, is it close to a window? AC
Edited 11/13/2007 5:49 pm by ClaysWorld
..."My question is this. Is it really a requirement for AFCIs in a bedroom? "
your inspector said it is, and it is his jurisdiction
I haven't looked at the 2008 NEC and there was so much talk about these things being required EVERYWHERE in a house ....... but bedrooms were required, at least since 2005.....ooops make that 1999
you know what the problem is, so just fix it and get your final.
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., wer ist jetzt der Idiot ?
Edited 11/13/2007 4:57 pm by maddog3
Dan's right.
Your 3-wire circuit needs a 2-pole AFCI breaker. There's nothing wrong with the wiring other than this code change. And unless the condo is wired in pipe there's no way to run another neutral all through that circuit.
Ed
The condo is wired with flexible metal conduit, so running additional wires is eminently doable. (Obviously, running new wires is done with the electricity off.)
But, just to double check things, when I remove the red hot wire from the AFCI breaker and attach the black one (the red is not hooked up) the breaker trips. This tells me that something else is "wrong". Before I spend the sheckels for the two pole, is it worth the effort to try this approach? Is a two pole AFCI breaker really for two 120 volt circuits?
I'm mentally prepared to trace the entire two circuits and pull another neutral so that the problem goes away, tomorrow. If I don't have to do that I'd buy everybody a margarita ...
John
Next thing to do is to disconnect all three insulated wires and make sure you don't show any connectivity between any of them and ground.
If your view never changes you're following the wrong leader
Sorry John, I didn't read your first post carefully.
If the breaker trips. the other real possiblity is a ground-fault problem, which will trip an AFCI breaker. This could be something as simple as a bare ground wire touching a neutral screw on a receptacle device.
Dans suggestion of checking for continuity is good. But be certain to check between ground and neutral also.
Yes, disconnect all three wires and then check between them (especially neutral) and ground. Any continuity at all is bad -- either the neutral is shorted to ground or it's crossed with a neutral from another circuit.Another thing you could run into is the breaker tripping only when certain outlets are used. This would occur if the outlet uses hot from one circuit and neutral from another.
If your view never changes you're following the wrong leader
Thanks DanH, edlee. I'll do as you suggest. My expectation is that I'll find another neutral tied in here. I'm going to run a new neutral so that I am not using the same neutral for both the red and black circuits (which are on different buss bars, etc.). And while I do that I'm going to find and fix the tied neutrals.
John
If by flexible metal conduit you mean what is often called 'armored cable' (it comes with the wires already in the cable, then I was thinking NO, you can't run another wire in it. I think there is a risk of damaging the insulation on the wire pulling it through.Plus there might be a sizing issue.But I could be wrong.
This isn't BX (armored) cable. It is flexible metal conduit that is run and then the wires are fished through it. It is half inch in size ... think EMT at half inch and the size is comparable.
John
johnhardy,
In this area , the "BX" is called MC cable, and what you are describing sounds like Greenfield. If it has a grey weather proof coating over it, we call it seal-tight. I wonder if it's a regional thing on what it is called? Like, anything with a metal jacket is called "BX"? It may be hard fishing wires through Greenfield, with connectors and any sag's in it. It may be rough going, it's not real smooth on the inside. Just my opinion.
Northeastvt
It's not liquitite. It's flexible metallic conduit ... think MC in half inch size. It is required here in California for condos. You cannot use romex. In fact, I ran some speaker wire ... yes speaker wire ... and the inxpector made me pull it down and run it in conduit as well. Talk about overkill.
John
johnhardy,
I was thinking Greenfield, that is very flexible, like BX or mc without the wire in it. As far as the speaker wires, yes it was. What do you have to run thermostat wire in? (3" ridged? :) I just can't imagine being in a place that requires that kind of bs. Do they hire people to spin around in there chairs on there slow day's and just try to come up with something that would make there job more secure? And everything on the east coast causes cancer in California, (that's how it's labeled.). I usually read the label, and say "Man, I am so glad I don't live in California, this stuff could kill me if I lived there!". It's not a bad thing, but sometimes I think it get's taken a little to far. I know I haven't helped you much, but thank's for giving me a chance to vent;)
northeastvt
In this area , the "BX" is called MC cable, and what you are describing sounds like Greenfield. If it has a grey weather proof coating over it, we call it seal-tight. I wonder if it's a regional thing on what it is called? Like, anything with a metal jacket is called "BX"?
Bx, MC, sealtite and greenfield are all different animals. Bx is a trade name for AC , or Armored Cable with its' own code section. MC is "Metal Clad", different from Bx and has it's own code section. Greenfield is a trade name for flexible metal conduit, usually called "flex" and has its' own code section. Sealtite is "Liquid-tight flexible conduit", either metallic or non-metallic, and has its' own two code sections.
The big noticable difference between MC and Bx is that MC has a full-sized insulated ground wire in it. Bx does not and relys on the sheathing to carry the ground. I hardly use Bx anymore, my most common use of it is to wire residential boilers.
Ed
Edited 11/14/2007 9:27 pm ET by edlee
edlee,
I realize they are different animal's. I didn't realize that BX was still available. Boilers and such are usually wired with mc here. Greenfield/ flex when you need to pull your own wires and need a larger diameter. Sealtight ,metal or plastic for wet locations. Good to hear your post and others. I only do residential, no inspections/permit's (they are not required here.). I did electrical work full time for 7 or 8 years, and 6 years of classes, but that was 10years ago. I try to stay on top of changes/ new codes etc. but it is only a small portion of the kind of work I do now. That's why I spend so much time here, can't ever stop learning,can never know everything:)
northeastvt
Vermont has a real hands-off approach to permits and inspections, doesn't it?
(You know what they call a long pull-chain in a stairwell? A Vermont 3-way)
I like bx on the boilers because of the tiny wiring compartments in the circulators, aquastats and such. It's easier to not have the additional wire. I figure with all that copper, steel and cast iron that the grounding is pretty secure.
But now those new-fangled European boilers are here, with plastic compartment housings and so-type cable connections, so bx is out..............
Ed
Edited 11/14/2007 10:28 pm ET by edlee
Edlee,
With a few eye hook's and some extra string, we can do four way's to. :>
Northeastvt
With a few eye hook's and some extra string, we can do four way's to. :>
Ha ha...............progress isn't always such a good thing, is it?
I've gotten trips with AFI or GFI if I tightened down too much on some wire insulation. There is enough leakage to pop it right away once current starts flowing through the circuit, like turning something on that is plugged in at a downstream outlet. With nothing powered but the wires are live, no popped circuit.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
I've gotten trips with AFI or GFI if I tightened down too much on some wire insulation.
Huh? What is it you're tightening down on the insulation.........you mean Rx staples or something like that?
Ed
Maybe he means fence staples.
If your view never changes you're following the wrong leader
I use Romex and metal boxes, with metal box entry clamps. Sometimes the wire gets crossed inside the clamp before I tighten in down, so the clamp tightens both wires to eachother and compresses the insulation. It won't trip a regular breaker, but it will trip a GFI/AFI.
I've also had a light circuit run from a bathroom GFI that would trip occasionally... I think from condensation in the EMT. Only thing I could think of. It only happened when the temp dipped suddenly.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
If I remember the details this is a multiwire circuit, with L1, L2, and N.And if a single pole AFCI is connected L1 and N that portion of the circuit works.But if connected L2 and N then the AFCI trips.If N was connected to other neutrals or ground then it would also trip in the first case. More likely that either there a load on L2 that is connected to ANOTHER NEUTRAL or to a ground or that t his is bad insulation, at some point, between L2 and ground or the neutral on another circuit.Just pulling a 2nd neutral most likely won't solve the problem. But in the process of connecting it up then the problem might be found or bypassed during the rewiring witthou even realizing it..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Is there much else on those two circuits? Do you really need two separate circuits for two bedrooms? Unless the code has changed since I last did this, it should be possible to combine them and buy only one single pole AFCI, if you can move other loads to other circuits.
-- J.S.
it should be possible to combine them and buy only one single pole AFCI,BINGO we've done this and it works well for old houses. You need a pretty savvy guy to get it right though. ------------------
"You cannot work hard enough to make up for a sloppy estimate."
Yeah, you can only do it if (A) there are no 240V loads, (B) the combined load on both hots is below the rating of the neutral, and (C) the installed breaker is sized to the neutral. The two hots would be pigtailed together in the panel and fed from the single-pole AFCI.Of course, this won't solve the "promiscuous neutral" problem that is presumably causing the breaker to pop. If this is an old house with some K&T then shared neutrals are all too common.
If your view never changes you're following the wrong leader
You said you remove the red wire from the breaker and attach the black, it trips immediately. Is the breaker off when you swap the wires? Does it trip when you try to turn it on?
It's off when I switch the wires, and trips when I turn it on. I don't know how these things work, but I suspect that the neutral is tied with other neutrals and there is power returning down the neutral that isn't flowing out the hot wire ... causing the trip.
But that should also be true when the red wire is attached, and it doesn't blow in that configuration.
I'll just trace everything tomorrow and change things around ... adding a separate neutral for the black circuit, and making sure that the neutrals are not tied together. C'est la vie.
John
Yes, like a said, disconnect all three insulated wires, and if the neutral is still tied to something that's your problem.
If your view never changes you're following the wrong leader