Bath Room Electrical?

[hr3]

I was under the impression that code requires bedrooms and bathrooms to be AFCI (Arc Fault Circuit Interrupter) protected; but I could be wrong as I'm no NEC guru.

Basically the code requires every 120v circuit in residential applications that is not GFCI protected to be AFCI protected..

 

[JB4310]

also, on the shared circuits your using, you say that the hot legs are on the same phase.

No, mine are on opposites.

The worst case for the neutral is if you have 20 amps on one circuit and zero on the other, then you get 20 amps back through the neutral.)

The downside of the common neutral circuit is that if you need GFCI protection, the only way to get it is to use a 2 pole (ganged) GFCI breaker which is very expensive.

I don't get how that would be different, having 20 amps on one circuit, putting 20 on the neutral, isn't it the same with a reg circuit not sharing a neutral? I may be missing something.

Also, I have several shared neutral circuits, I'm positive some of those have GFIs on them, and they are just regular GFI outlets, not breakers. No known problems.
These are the smart gfis that wont energize if not wired correctly.

Generally upside outlets are to make it easier for the homeowner to identify which outlet is switched.

I think grsthegreat gave a good example with the metal cover shorting terminals. the reasoning makes sense to me, when a cord strains down it leaves the hot and neutral blades partly exposed, not large enough a gap to touch with fingers, but some metal object could fall in there causing a hazard. I was thinking of my daughter with her metal chains, falling behind a nightstand.

Basically the code requires every 120v circuit in residential applications that is not GFCI protected to be AFCI protected..

So is it easier/ better to just do the whole house in GFCI? If AFCI is so finicky. They should have a 100 or 200 Amp GFCI main breaker?

JB.

 

[KennyG]

GFCI on shared neutral circuits:

If you have individual GFCI outlets, that's no problem. The problem (as I understand it) comes in when you use the GFCI outlet in the wire through mode to protect additional normal outlets. In that case, if you have independent loads on both circuits, the shared neutral current will not match the hot leads and the GFCI will trip. Same problem if you have individual breaker GFCIs and not the expensive two pole version.

This is where the tradeoff comes in on cost on GFCI circuits. Say you have two parallel 20 amp circuits and each will have 5 outlets. You can run two parallel 12/2 cables and put GFCI outlets in the first box on each circuit and protect all the outlets. On the other hand, you can run a single 12/3 cable but, if GFCI is required, you need either the $150 2 pole GFCI breaker or GFCI outlets for each outlet.

You are right on the case where the load is all on one hot lead, the neutral current matches the hot lead and it's just like an independent circuit. When you have loads on both leads is when it changes. If you have 20 amps on one side and 10 on the other, the neutral will have 10 amps and it will be 180 degrees out of phase with the 10 amp load circuit.

 

[grsthegreat]

First question, you are correct. Since the two hot legs are 180 degrees out of phase, if you are drawing 20 amps on each, they balance and the power essentially feeds back and forth through both hot legs. The neutral has zero current. The worst case for the neutral is if you have 20 amps on one circuit and zero on the other, then you get 20 amps back through the neutral. Think about it - if you are running a 220 volt load on the two hots, you can disconnect the neutral and it would still run fine. (Don't try this at home, kids.)

The downside of the common neutral circuit is that if you need GFCI protection, the only way to get it is to use a 2 pole (ganged) GFCI breaker which is very expensive.

I'm not sure what the other poster actually meant by "drop a neutral". If the neutral becomes disconnected, neither of the 110 circuits will work at all. (A 220 load could be powered, but only if you have a socket wired to both hot leads.) If you short one of the hot leads to the neutral, you would theoretically have 220 across the 110 socket, but you would also pop the breaker, so I'm not sure why this is concern. I guess if you disconnect the neutral at one place and short it at another, you'd get 220 on a 110 socket, but that's pretty farfetched.

The only safety concerns I've heard about with this arrangement is that if you have individual breakers you could trip one breaker and still have power on one side of the circuit in the box and also the concern that if you hook both hot legs to the same phase, you can overpower the neutral.

dropping a neutral can and does happen if the neutrals in one box are disconnected either by accident or while repairing a live circuit. you can and will get 220 thru the hookup. ive seen it happen. i was trying to diagnose an issue where all the lights in a section of the house would suddenly go super nova bright. they would last awhile before burning out. I went and tested the socket....220. I found an outlet where a group of neutral wires had become disconnected. after reconnecting them, the lights went back to 110.

talked to my inspector, he said that can happen in the Edison (shared) neutral circuits)...thats why most people dont use them.

 

[grsthegreat]

No, mine are on opposites.




I don't get how that would be different, having 20 amps on one circuit, putting 20 on the neutral, isn't it the same with a reg circuit not sharing a neutral? I may be missing something.

Also, I have several shared neutral circuits, I'm positive some of those have GFIs on them, and they are just regular GFI outlets, not breakers. No known problems.
These are the smart gfis that wont energize if not wired correctly.





I think grsthegreat gave a good example with the metal cover shorting terminals. the reasoning makes sense to me, when a cord strains down it leaves the hot and neutral blades partly exposed, not large enough a gap to touch with fingers, but some metal object could fall in there causing a hazard. I was thinking of my daughter with her metal chains, falling behind a nightstand.





So is it easier/ better to just do the whole house in GFCI? If AFCI is so finicky. They should have a 100 or 200 Amp GFCI main breaker?

JB.

when i wire schools, we use whole system GFCI breakers....sometimes 1600 amp GFCI breakers. they have to be set by the manufacturer after completion of the job. They are a great protection; however, if they trip....bammo no power anywhere.

kind of last ditch protection i guess.

 

[bdeboer]

I've come to the conclusion that a lot of code changes are meant to keep the code writers in business, especially if they change something that has worked fine for ages.

My opinion is that some of these rules are added in by manufacturers rep's. sitting on the boards. They get an instant profit center out of the deal.

 

[Iplayfarmer]

when i wire schools, we use whole system GFCI breakers....sometimes 1600 amp GFCI breakers. they have to be set by the manufacturer after completion of the job. They are a great protection; however, if they trip....bammo no power anywhere.

kind of last ditch protection i guess.

So, if they trip does the manufacturer have to come a reset them?

 

[grsthegreat]

So, if they trip does the manufacturer have to come a reset them?

no, anyone can reset it, but the entire school goes dark

the manufacture just sets the internal workings of the thing....initial trip ratings

 

[hr3]

So is it easier/ better to just do the whole house in GFCI? If AFCI is so finicky. They should have a 100 or 200 Amp GFCI main breaker?

:confused2: Nooo....

when i wire schools, we use whole system GFCI breakers....sometimes 1600 amp GFCI breakers. they have to be set by the manufacturer after completion of the job. They are a great protection; however, if they trip....bammo no power anywhere.

Per nec any service over 1200 amps is GFCI protected

This is where the tradeoff comes in on cost on GFCI circuits. Say you have two parallel 20 amp circuits and each will have 5 outlets. You can run two parallel 12/2 cables and put GFCI outlets in the first box on each circuit and protect all the outlets. On the other hand, you can run a single 12/3 cable but, if GFCI is required, you need either the $150 2 pole GFCI breaker or GFCI outlets for each outlet.

Again not so,, Gfci's do not look back on the power lines,, If you run a 12/3 to a junction box and take 2 12/2's out of the box to a gfci outlet then on to the rest of the protected outlets it will work fine..

 

[KennyG]

Again not so,, Gfci's do not look back on the power lines,, If you run a 12/3 to a junction box and take 2 12/2's out of the box to a gfci outlet then on to the rest of the protected outlets it will work fine..

That's what I was saying, you have to go to parallel 12/2 downstream UNLESS you put GFCI in each outlet. An example that I actually have: A 12/3 run that has a series of 6 square boxes on it. The first, third and fifth boxes have a GFCI outlet with a second conventional outlet wired through the GCFI, all hooked to the "red" phase. The "black" phase is just wired through these boxes. the second, fourth and sixth boxes have the same setup except wired to the "black" phase. As a result, I ran about 100 ft of 12/3 instead of 200 ft of 12/2 but used 6 GFCI outlets instead of 2. A big deal? No but that's the way I did it.