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Old 10-27-2019, 09:24 AM   #1
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Two existing 12/3 wires in kitchen, best use?


I have two existing 12/3 wires (shared neutral) running to the kitchen and wondering how to best utilize these.

It seems obvious to use one for the dishwasher/disposal on a split receptacle, so one dedicated circuit/outlet for each "appliance". Do these have to be GFCI?

For the other, I am unsure whether to use it for the two branches of outlets or not. I am aware that each receptacle on a branch should have neutral pigtailed, but how does a gfci factor into that mix? Can one gfci feed the rest on the branch, or would that cause problems and require each receptacle on a branch to be gfci?

If each outlet must be gfci, then it seems more cost effective to use the second shared neutral split for microwave/fridge, would that be acceptable?

I still have to run extra 12/2 wires anyway (whether it is for micro/fridge, or 2 outlet branches). I could re-run everything with their own 12/2 but it would be nice to salvage some existing wiring. If it won't work at all, I can run all 12/2 into the kitchen...

Last edited by gslenk; 10-27-2019 at 09:29 AM.
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Old 10-27-2019, 09:35 AM   #2
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Re: Two existing 12/3 wires in kitchen, best use?


Consider adding your general location to your profile.
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Old 10-27-2019, 09:52 AM   #3
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Re: Two existing 12/3 wires in kitchen, best use?


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Consider adding your general location to your profile.
Done. I assume that means local codes may be relevant in this decision? My area uses 2014 NEC.
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Old 10-27-2019, 11:25 AM   #4
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Re: Two existing 12/3 wires in kitchen, best use?


Dishwasher requires GFCI protection under 2014 NEC, and both dw and disposal require AFCI

Last edited by jhil; 10-27-2019 at 11:30 AM.
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Old 10-27-2019, 12:47 PM   #5
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Re: Two existing 12/3 wires in kitchen, best use?


So either cough up ~$80+ for a dual afci breaker to make 12/3 work, or run separate 12/2 wires (on ~$30 each single breakers)? Probably looking at ~50ft runs. They terminate above the countertop at usual outlet locations.

Looks like running new 12/2 wires is leading by a little bit. Is there anything the 12/3 wires would be good for?
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Old 10-27-2019, 01:07 PM   #6
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Re: Two existing 12/3 wires in kitchen, best use?


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Originally Posted by gslenk View Post
So either cough up ~$80+ for a dual afci breaker to make 12/3 work, or run separate 12/2 wires (on ~$30 each single breakers)? Probably looking at ~50ft runs. They terminate above the countertop at usual outlet locations.

Looks like running new 12/2 wires is leading by a little bit. Is there anything the 12/3 wires would be good for?
You can use GFCI ($15)or AFCI/GFCI ($30)receptacles on your 12/3 wiring with standard 2 pole breakers. Pigtail the common neutral to the devices.
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Old 10-27-2019, 01:13 PM   #7
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Re: Two existing 12/3 wires in kitchen, best use?


If you aren't going to use the existing 12/3 to supply 2 circuits consider using them to supply 1 circuit each.
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Old 10-27-2019, 02:28 PM   #8
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Re: Two existing 12/3 wires in kitchen, best use?


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You can use GFCI ($15)or AFCI/GFCI ($30)receptacles on your 12/3 wiring with standard 2 pole breakers. Pigtail the common neutral to the devices.
Is an AFCI/GFCI receptacle is an option to terminate for a DW/Disposal? Can they be made (or manufactured ready) to separate the branches? Or were you referring to countertop receptacles?
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Old 10-27-2019, 02:30 PM   #9
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Re: Two existing 12/3 wires in kitchen, best use?


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If you aren't going to use the existing 12/3 to supply 2 circuits consider using them to supply 1 circuit each.
May be a worthwhile option.

If anyone has any ideas regarding a legitimate use of these conductors, I am all ears. Otherwise it sounds like a general (silent) consensus to abandon/remove them.
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Old 10-27-2019, 02:33 PM   #10
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Re: Two existing 12/3 wires in kitchen, best use?


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Is an AFCI/GFCI receptacle is an option to terminate for a DW/Disposal? Can they be made (or manufactured ready) to separate the branches? Or were you referring to countertop receptacles?
Install 2 receptacles in a 2 gang box. Pigtail the neutral to both, connect black to one and red to the other.
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Old 10-27-2019, 08:15 PM   #11
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Do not abandon the 3 conductor wiring. They each provide 2 circuits, just feed any GFCI receptacle after splicing to the neutral. You just cannot split wire a receptacle. Alternate option is to use a 2 pole GFCI breaker.
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Old 10-28-2019, 07:01 AM   #12
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Re: Two existing 12/3 wires in kitchen, best use?


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Install 2 receptacles in a 2 gang box. Pigtail the neutral to both, connect black to one and red to the other.
Do this for two countertop circuits as well with GFCI/AFCI receptacles
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Old 10-28-2019, 08:53 PM   #13
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Re: Two existing 12/3 wires in kitchen, best use?


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Do not abandon the 3 conductor wiring. They each provide 2 circuits, just feed any GFCI receptacle after splicing to the neutral. You just cannot split wire a receptacle. Alternate option is to use a 2 pole GFCI breaker.
OK I got it. Can I add more receptacles to one "side" of the 12/3? If so, must I splice 12/2 into the relevant 12/3 neutral/hot pair before the first GFCI on that side? Or am I able to use the load side of the first GFCI to cover "downstream" receptacles?

For example (not using load side), on the black side of 12/3, splice 12/2 black/white into the 12/3 black/white before the original/first GFCI on that side. Then continue pig-tailing all downstream outlets from there, all GFCI, on the line side only. (similar for red side except 12/2 black to 12/3 red etc...)
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Old 10-28-2019, 09:10 PM   #14
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Re: Two existing 12/3 wires in kitchen, best use?


I have always thought this would work but don't know.

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Old 10-28-2019, 09:36 PM   #15
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Re: Two existing 12/3 wires in kitchen, best use?


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I have always thought this would work but don't know.

Exactly


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