Is this wiring diagram OK?

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Old 07-16-10, 06:24 PM
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Is this wiring diagram OK?

I'm planning a new circuit for two split receptacles, one on either side of the kitchen sink - T-slot GFCI's fed directly from the panel on a 20A breaker, using 12-3 wire.



There will be nothing downstream from the second outlet, so I'm unclear. Is the black wire leading away from the first outlet omitted? Same with the white and red going from the second outlet?

This will then give me two split receptacles I want? Any special grounding required?
 
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Old 07-16-10, 06:55 PM
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Since you are using a common white wire (MWBC), this should ideally be connected to a DOUBLE POLE breaker. If you are using single breakers, they MUST be right next to one another. You have to make sure the red and black are on opposite poles to avoid overloading the neutral. Another issue you can possibly run into is if you are pulling a permit for this, depending on which code your AHJ uses, you may be required to use AFCI breakers as well. You can not connect a MWBC to standard AFCI breakers. You might just be better off running separate 12/2 from the panel to each GFCI and leave it at that.

The way you have it drawn though, it will NOT work with the neutral on the LOAD side of the first GFCI. The first GFCI will always show a load imbalance/leakage from the second one, therefore it will always trip as soon as it's powered up. I would only run 12/2 between the first and second box, because there is no way to carry the load side of the black circuit through for future expansion using 12/3. You would need two separate neutrals to carry both circuits through to the second box. The neutral for the red circuit must be directly connected to the feed neutral on the LINE side of the first GFCI.

No special grounding, just all grounds connected together, connected to the box if it's metal, and connected to both GFCI's ground terminals.
 
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Old 07-16-10, 06:59 PM
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I agree with JerseyMatt. You need a second neutral, none of the out lest is going to work.
 
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Old 07-16-10, 06:59 PM
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You can not split wire a GFCI receptacle, IE: a different circuit on each half of the device. That said your diagram is more or less correct. I suggest pig-tailing all the wires in each box, unless a pigtail is unneeded, then just splice through. You can run a 12/3 and just cap off the black in the second box if it is unneeded. If you are on 2008 code you will have to use a 2 pole breaker for this multiwire circuit.
 
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Old 07-17-10, 04:59 AM
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it is a code violation to feed through the neutral on a MWBC. Must be pigtailed
 
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Old 07-17-10, 05:02 AM
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Originally Posted by esalman View Post
I agree with JerseyMatt. You need a second neutral, none of the out lest is going to work.
Sure they will. Why cant he pigtail them and only use the line side on the GFCI, putting a GFCI at each location required? Its not the most cost efficient way but it will work
 
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Old 07-17-10, 07:56 AM
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Just a quick note that the Op is in Canada. Split wired receptacles used to be required, but I believe that that may have changed.
 
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Old 07-17-10, 11:22 AM
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Originally Posted by Danny7633 View Post
it is a code violation to feed through the neutral on a MWBC. Must be pigtailed
Didn't know it was actually violation, because it wouldn't work at all.. The first GFCI would never reset. I'd have thought it would have to be a usable circuit in order for them to bother putting it into the code..

Originally Posted by Danny7633 View Post
Sure they will. Why cant he pigtail them and only use the line side on the GFCI, putting a GFCI at each location required? Its not the most cost efficient way but it will work
That's exactly what I said. The two neutrals comment refers to the fact that you can't have both circuits wind up in the second box (I assume to expand later), GFCI protected, with only one neutral. Every GFCI circuit must have its own neutral otherwise it will never reset because there will always be a current imbalance

Originally Posted by pcboss View Post
Just a quick note that the Op is in Canada. Split wired receptacles used to be required, but I believe that that may have changed.
I'd say it probably changed when they made GFCI's a requirement.. Since there is no such thing as a split GFCI..
 
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Old 07-17-10, 12:36 PM
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Matt...there is a way you could do it you would wire line into line in of Gfci 1 line to line in of Gfci 2 then line to the extended circuit never touching the load end of the gfci

If it needed to be done in the mwbc format i would think it could be done the same but with pigtails for the neutral
 
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Old 07-17-10, 12:51 PM
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You're the second person to say "no it can be done this way", then repeat exactly what I said. I know that, and I explained it twice already.

You are still missing the point of my original reply. There is no possible way to have, in the second box, the black circuit protected by GFCI 1, and the red circuit protected by GFCI 2, using a MWBC. It just will not work. You would need two neutrals.
 
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Old 07-17-10, 03:01 PM
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If I may interject, You boys are talking about two different things. Matt is saying it won't work because the picture shows what looks like the OP using the LINE and LOAD of the device. Braether is saying it would work fine if everything was pigtailed and the load side is not used on either device. You both are correct in what you are saying. Your just talking about different things of the circuit.
 
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Old 07-17-10, 03:16 PM
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Originally Posted by JerseyMatt View Post
Since you are using a common white wire (MWBC), this should ideally be connected to a DOUBLE POLE breaker. If you are using single breakers, they MUST be right next to one another.
I'm not entirely sure about Canada, but if you are using the NEC this is wrong. 210.4(B) states: "a means shall be provided to disconnect simultaneously all ungrounded conductors". This basically means you must use a double pole breaker. Single breakers next to one another are not allowed (unless you get a handle tie kit that mechanically turns them into a double pole).

Using a double pole also solves the problem of making sure the two hots aren't on the same side of the phase. Since the hot buses alternate going down the panel. Still, the important point is that with a MWBC you have to have a way to klll both hots whenever you kill one.

My suggestion would be to just skip the common neutral. Besides the fact that the load side of a GFI can't share neutrals, 12/2 is often so much cheaper that there isn't much of a cost savings to be had running 12/3. And while this isn't likely to be an issue with a kitchen circuit, any circuit that powers a lot of electronics is not so good to have a common neutral anyways (although this problem is much more severe in commercial 3-phase systems).
 
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Old 07-17-10, 03:45 PM
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Originally Posted by JerseyMatt View Post
y. There is no possible way to have, in the second box, the black circuit protected by GFCI 1, and the red circuit protected by GFCI 2, using a MWBC. It just will not work. You would need two neutrals.
yes I know and I know you know the gfci would never reset without 2 neutrals. there is no need to get offended the OP would be much better off simply running 2 separate pieces of 12-2 the first gfci or 3 runs of 12-2 if he needs to have unprotected outlets down the line

have a nice day
Ben
 
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Old 07-17-10, 04:07 PM
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Originally Posted by mukansamonkey View Post
I'm not entirely sure about Canada, but if you are using the NEC this is wrong. 210.4(B) states: "a means shall be provided to disconnect simultaneously all ungrounded conductors". This basically means you must use a double pole breaker. Single breakers next to one another are not allowed (unless you get a handle tie kit that mechanically turns them into a double pole).
That's only NEC2008. Up to 2005, you could still have a MWBC on separate breakers as long as it wasn't serving a split receptacle or a single appliance outlet. But assuming it was 2008, it wouldn't be allowed to be a MWBC anyway because it would require AFCI breakers since it's a new circuit. And yes, I realize now we are talking about CEC, so it's moot.

Originally Posted by braether3 View Post
yes I know and I know you know the gfci would never reset without 2 neutrals. there is no need to get offended the OP would be much better off simply running 2 separate pieces of 12-2 the first gfci or 3 runs of 12-2 if he needs to have unprotected outlets down the line

have a nice day
Ben


Again, you just said I'm wrong, then said the exact same thing from my original reply. I give up.
Originally Posted by JerseyMatt View Post
You might just be better off running separate 12/2 from the panel to each GFCI and leave it at that.
 
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Old 07-17-10, 04:20 PM
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Originally Posted by JerseyMatt View Post
That's only NEC2008. Up to 2005, you could still have a MWBC on separate breakers. But assuming it was 2008, it wouldn't be allowed to be a MWBC anyway because it would require AFCI breakers since it's a new circuit.
Actually I quoted that from the 2005 code... I never got around to buying the 2008 because I haven't been working in the industry for the past year or so. Construction work is really dead where I'm at.

In any case, as you pointed out (and other people haven't entirely understood), it'd be better for the OP to run two pieces of 12/2 and skip the neutral entirely. At which point this discussion of the finer points of MWBC gets chucked... which is a good thing really. better to split the neutral and avoid any potential neutral-sharing issues down the line.

Oh! Another reason to run two separate neutrals: In my experience, outlet-based GFIs fail with much more frequency than the ones inside the circuit breakers. For circuits like the kitchen appliance ones, that have to be 100% GFI, I much prefer having the GFI in the breaker. At which point a shared neutral doesn't work anyways. Running 12/3 removes this as an option.
 
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Old 07-17-10, 05:32 PM
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I recently ran into this sort of situation trying to straighten out some wiring in a house my niece bought from a bank. Down stream from one GFCI a bunch of white wires were tied together in more than one box, and the GFCI would not reset. I believe it was because neutral current from more than one circuit was mixing back to that one wire.


That seems like the case in the diagram here. He would have mixed current ultimately in the white wire and the GFCI would trip on imbalance. Is that the main issue?
 
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Old 07-17-10, 05:59 PM
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Originally Posted by mukansamonkey View Post
Actually I quoted that from the 2005 code... I never got around to buying the 2008 because I haven't been working in the industry for the past year or so. Construction work is really dead where I'm at.
2005:
210.4
(B) Disconnecting means: Where a multiwire branch circuit
supplies more than one device or equipment on the same
yoke
, a means shall be provided to disconnect simultaneously all ungrounded conductors supplying those devices or equipment at the point where the branch circuit originates.

"on the same yoke" means a split wired receptacle or similarly wired single device utilizing both hot lines.

240.20 (B)
(1) Multiwire Branch Circuit. Except where limited by 210.4(B). individual single-pole circuit breakers, with or without identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.

2008:
210.4
(B) Disconnecting means: Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.

240.20 (B) (1) still exists in 2008, but it is completely nullified by 210.4 (B)
 
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Old 07-17-10, 06:37 PM
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Originally Posted by JerseyMatt View Post


Again, you just said I'm wrong, then said the exact same thing from my original reply. I give up.

I never said you were wrong buddy I said we both know how a gfci works and our job is to explain that to the OP's....you know the saying great minds think alike...lets just think of it that way
I don't doubt your intelligence in the least.
 
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Old 07-18-10, 07:13 AM
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Thanks, everyone!

To keep things simple, I've decided to run two separate 12/2 circuits.

Sorry if my post caused some tension...
 
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Old 07-18-10, 09:29 PM
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Its fine man thats what we are here for... come back again Beer 4U2
 
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