Shared Neutral to GFCI

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  #1  
Old 05-28-15, 08:51 PM
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Shared Neutral to GFCI

I spent some time today trying to identify the breakers at the main panel of my 1927 home. After a shock or two and some blown breakers , I found that two kitchen outlets are using a shared neutral. One outlet is for the microwave, the other is an 'extra' outlet. Looks like the neutral is split from the breaker with a branch running to each outlet.

Is this correct, or should I try and pull a new neutral?

Here's a pic, hope it makes sense:

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Old 05-28-15, 08:57 PM
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If you have 240 volts between red and black it is okay.
 
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Old 05-28-15, 09:14 PM
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Meaning two 20A breakers, yes?

Follow up: Can I now branch additional GFCI outlets (two max) off the 'extra' one, or do I need to pigtail the neutrals for each?
 
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Old 05-28-15, 09:33 PM
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Meaning two 20A breakers, yes?
Only if they are on opposite legs. 240v is proof of that. They need to be handle tied.
do I need to pigtail the neutrals for each?
Yes.
 
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Old 06-06-15, 08:17 AM
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Just noticed this thread and have a quick question as I have the same situation for six circuits in my panel (three shared neutrals). I understand that there needs to be 220 volts between the two (red and black on opposite legs) to prevent exceeding ampacity on the neutral.

Why do the the breakers handles need to be tied together? If one trips then the other should still be okay from a neutral ampacity point of view. I can see tying them together to help ensure they are on separate legs but is there another reason beyond that? None of mine are tied together though they are on separate legs.

The code also has some language requiring neutral pigtails at outlets for this type of setup, the point being that you can't pass a neutral through an outlet (in one screw out the other). I think this is to prevent inadvertently disconnecting the other circuits neutral. Does this only apply where the two circuits branch off from each other?
 
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Old 06-06-15, 08:57 AM
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Why do the the breakers handles need to be tied together?
2011 code and later requires multi-wire circuits (circuits with a shared neutral) to have a common disconnect. That does not mean it MUST be a two pole breaker, however that is the easiest way to do it. Wiring done before that would be grandfathered in.

Does this only apply where the two circuits branch off from each other?
No. The code requires that a milti-wire circuit neutral connection cannot rely on a device for it connection. Device meaning receptacle, switch, etc.
 
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