Shared neutral for kitchen circuits

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Old 10-06-16, 12:15 PM
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Exclamation Shared neutral for kitchen circuits

Hi,

Per my post http://www.doityourself.com/forum/el...ml#post2567502 I'm wiring our kitchen reconstruction.

On one wall I'll have a circuit for the vent hood and a small appliance circuit.

Is it OK to use 12-3 NMW and use a shared neutral instead of running two separate cables? Any downside to this idea?

Thanks guys!
 
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Old 10-06-16, 12:29 PM
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You can use 12-3 configured as a MWBC up until the first GFCI device. After that, you must have separate neutrals as the LOAD side of a GFCI device is incompatible with a shared neutral. The MWBC will need a two-pole (handle tied) breaker.
 
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Old 10-06-16, 01:43 PM
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Assuming you have a total of two 20 amp GFCI protected circuits in the kitchen. What Ben said.
 
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Old 10-06-16, 02:29 PM
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You might know this already, just in case.
Where the MWBC splits (maybe a receptacle), the neutral wires must be connected with a wire nut with a single pigtail to the receptacle.
You can't use the receptacle terminals to continue neutral downstream when splitting.
 
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Old 10-06-16, 02:32 PM
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If you do a MWBC I suggest 2 single pole independent trip breakers with a handle tie. A normal 2 pole common trip breaker will kill both circuits if only one is overloaded.
 
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Old 10-06-16, 02:51 PM
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Only caution is that you probably need AFCI breakers and finding the right ones to support a MWBC could be a problem depending on your panel.
 
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Old 10-06-16, 06:33 PM
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The requirement for AFCI protection on kitchen circuits started in 2014. If your location is using an earlier version of the NEC, no AFCI is required.
 
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Old 10-08-16, 01:44 PM
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Sounds troublesome especially on the breaker end of my Crouse Hinds box. I'll just run 2 cables.

Thanks guys!
 
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Old 10-09-16, 05:00 AM
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Don't forget that of the various circuits running to or through the kitchen, two must serve just receptacles on the counter, elsewhere in the kitchen, or in a pantry or dining room.

Ground fault circuit interrupter receptacles can be put on a multiwire branch circuit with a GFCI receptacle at each receptacle location. The load terminals would be left empty, or, given sufficiently large outlet boxes, a 2 wire cable may continue from the load terminals to any other acceptable desired location including leapfrogging to another outlet box on the same daisy chain.
 
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Old 10-10-16, 05:17 AM
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"with a GFCI receptacle at each receptacle location"

Not one GFCI at the first location, but each receptacle?
 
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Old 10-10-16, 05:50 AM
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One GFCI per run with regular receptacles off the LOAD side. Having more than one GFCI even though you don't use the LOAD side will cause nuisance trips.
 
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Old 10-10-16, 07:41 AM
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Thanks Chandler. By "load side" you mean the first receptacle in the daisy chain from the supply?
 
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Old 10-10-16, 09:37 AM
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The power goes into the line side. Any power to downstream is fed from the load terminals if gfi protection is needed.
 
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Old 10-10-16, 10:42 AM
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Power to the GFCI receptacle is connected to the "line" or "line side" terminals.

The "load" or "load side" terminals are the second set of terminals on the GFCI receptacle unit. The cable or wires (if any) attached here form a subcircuit that may continue on and feed other things and provide GFCI protection to those things.

The cable or wires attached to the load terminals cannot be the same cable or wires continuing the rest of an MWBC out of the outlet box to yet other things.

A continuing cable (or set of wires) can be attached directly to the incoming cable including a MWBC (with pigtails to the receptacle itself in the box) to continue the circuit with no additional restrictions but also without GFCI protection from a GFCI in the outlet box departed from. Thus the idea of additional GFCI receptacles in outlet boxes downstream.

We are not suggesting connecting a GFCI receptacle to a subcircuit that already has GFCI protection.
 
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Old 10-10-16, 12:45 PM
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Thanks guys. I think I have it.

The one SABC has a wall outlet, then that feeds the gas range outlet, that feeds the second wall outlet.

So GFC on the first wall outlet protects that whole circuit. Correct?
 
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Old 10-10-16, 12:50 PM
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I mis spoke, sorry. LINE is where power goes in.
 
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Old 10-10-16, 03:57 PM
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So GFC on the first wall outlet protects that whole circuit. Correct?
 
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Old 10-10-16, 04:45 PM
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So GFC on the first wall outlet protects that whole circuit.
Yes, if it is connected to the load side.
then that feeds the gas range outlet
Not really specifically a gas range receptacle. It is just another receptacle on the circuit that you can plug anything into. Gas ranges generally do not require a spacial circuit.
 
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Old 10-10-16, 04:50 PM
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Yes. You are not using a mwbc, so you will wire the GFI receptacles normally.

At the first box, source, the neutral and hot wires get connected to "Line" terminals. Downstream receptacles get connected to Load terminals.
Any one of the receptacles, the GFCI itself or load receptacles will trip the GFI when a fault is detected.

We get a lot of questions here on possible reasons a receptacle doesn't work. A tripped GFCI comes up a lot.
The GFI packaging contains stickers that are meant to identify a normal receptacle that is GFI protected at some other location.
 
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Old 10-10-16, 05:20 PM
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Thanks guys! Half the kitchen is rough wired now, so I think I've got it in my mind correctly.
 
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Old 10-10-16, 06:22 PM
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Let us know if you have anymore questions.
 
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Old 10-13-16, 02:49 PM
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Working on the other wall and have a new question:

I'm running a dedicated circuit for dishwasher and disposal. Is the box typically put in the wall or is it mounted in the cabinet under the sink once that's installed? Does it need a GFCI?
 
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Old 10-13-16, 05:19 PM
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You can mount the box inside the cabinet, it looks cleaner than cutting the cabinet back around the receptacle plate.
A lot of cabinet backs are thin and won't hold a screw to secure the box. I use Wall Dog anchor screws, they don't strip out in thin material or drywall.
 
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Old 10-14-16, 01:59 PM
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Thanks. Is that a typical steel box or does it need to be a box that works w/surface mount channel?
 
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Old 10-14-16, 03:45 PM
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A surface race box will look nicer but other boxes with adequate cubic inches can be used. A 4x4 box would be another choice.
 
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Old 10-15-16, 05:39 AM
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New issue w/GFCI's on SABC

Thanks for all the GREAT help with my project guys!

I now realize I have an issue w/part of my project regarding GFCI's on one SABC circuit.

SABC circuit #1 has three boxes, left, center, and right. The center box is where I brought the power feed into. It's mounted 10 inches above the floor for the gas range only and will not be visible when the kitchen is complete. The left and right boxes feed from there individually (no daisy chain).

So thinking about the GFCI advice given, it seems that I can't have one GFCI upstream (center box) of the other two, because that box will not be physically reachable to reset a tripped GFCI. I'll have to put one each in the left and right boxes and have a plain receptacle in the center range box.

Is there any code issue or other issue doing this?
 
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Old 10-15-16, 06:54 AM
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That's fine to have a GFCI at each location. Only the line terminals are used.

Pigtail all your wires for the receptacle behind the range.
 
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Old 10-15-16, 07:19 AM
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"That's fine to have a GFCI at each location. Only the line terminals are used." So I'm 100% clear on this:

I wasn't going to GFCI the range outlet because it would be impossible to get to if it tripped. Is that OK if the others are GFCI?
 
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Old 10-15-16, 07:23 AM
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Yes. The receptacle behind the range will be normal. At the range, wire nut all the hot and neutral wires with a single pigtail to the receptacle.
 
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