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Discussion Starter #1
Im a student getting ready to enter the program, so I hope its ok to ask a question or two (and if not, apologize)....

I am replacing some outlets for my parents. I am vaguely familar with NEC 300.13(B) and MWBC's but i need clarification.

I know it critical to pigtail the neutrals prior to the circuit spliting the neutral. However, I am unclear.... Is it neccesary to pigtail the neutrals after the two circuits split?

I realized that the outlets on both legs of the MWBC, after the box where the neutrals are split, are fed thru each other... not pigtailed. Do these need to be rewired?

Hopefully this question is OK in this forum, if not I will go back to lurking... I have learned alot from this forum while reading it in my spare time. Thanks. :thumbsup:
 

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I know it critical to pigtail the neutrals prior to the circuit spliting the neutral. However, I am unclear.... Is it neccesary to pigtail the neutrals after the two circuits split?
You don't have to pigtail them after they split.

Youre good to go.
 
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Let's say your using conduit. You don't splice the connection but strip off the insulation to wrap the screw of the device. Legal?
 

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Let's say your using conduit. You don't splice the connection but strip off the insulation to wrap the screw of the device. Legal?
As long as the wire doesn't rely on the device for continuity.
 

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aftershockews said:
Let's say your using conduit. You don't splice the connection but strip off the insulation to wrap the screw of the device. Legal?
. Yes , because you're not counting on the continuity of the device as a feed through . It's an unbroken conductor and the circuit integrity I still intact on device replacement , or that's what I think anyway , lol ?
 

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After the split no pigtailing is needed since if the device is taken out it will not break the neut and cause a voltage imbalance.
 

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Discussion Starter #8
Thanks for the clarification.

How come 300.13b doesnt specify that this requirement is only prior to it splitting?

Back to read-only mode.....
 

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Discussion Starter #10
Because It isn't a MWBC after it splits.
This is where my ignorance gets me. If its still the return path for one of the two phase conductors that share the neutral upstream, why isnt it technically considered a MWBC any more?

Back to read mode I promise....
 

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This is where my ignorance gets me. If its still the return path for one of the two phase conductors that share the neutral upstream, why isnt it technically considered a MWBC any more?.

I think my explanation isn't helping.

Its still "part" of a MWBC.

I will find some info for you.
 

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This is where my ignorance gets me. If its still the return path for one of the two phase conductors that share the neutral upstream, why isnt it technically considered a MWBC any more?

Back to read mode I promise....
Soe :)Welcome to the forum..:thumbup:


Let's make this easy,Let's say you've got 4 receptacles on a multywire branch circuit,every other receptacle you want to be hot from the red wire.

So you have 3 wire to each box and a 2 wire to the last box.

In the first box splice all the wires color for color tuck in the black wire first because you do not need a pig tale from the black,as you make up your grounds have a pig tail to ground the receptacle,as you make up the whites have a pigtail for the receptacle,as you make up the reds have a pigtail for the receptacle,second box do the same thing ,but, this time you will not pigtail the red so spice them up and tuck them in first.
 

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Here is a picture of a MWBC.

Does the illustration help you understand?


mwbc.jpg
 

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Discussion Starter #15
Although I said I was going back into the shadows just wanted to thank you Awg-Dqwg for the diagram, I understand better.

BTW: found a 1950's 2 prong outlet feeding thru the neutrals in a bad way. Backstabbed too, they pulled right out when the outlet was removed.

Was this ever acceptable? When did 300.13 become code? Have you ever ran across this in the field?

Happy Thanksgiving.
 

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Backstabbed too, they pulled right out when the outlet was removed.

Was this ever acceptable?

I think it is still acceptable.

Stick around and ask your questions.

There are guys here that have more experience than me about the questions you are asking.
 

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Discussion Starter #17
I think it is still acceptable.
I should have clariffied, this was before the neutrals splits. Freaked me out for sure.


In fact, in my parents house, all of the 120 circuits are MWBC. Is that screwy?
 

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I should have clariffied, this was before the neutrals splits. Freaked me out for sure.
I don't when, if ever that was allowed.



In fact, in my parents house, all of the 120 circuits are MWBC. Is that screwy?
Residential is not my strong suit, I don't know of anything that would prohibit it.
 

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This is where my ignorance gets me. If its still the return path for one of the two phase conductors that share the neutral upstream, why isnt it technically considered a MWBC any more?

Back to read mode I promise....
The fact that you are asking this question means that you have a very inquisitive mind. The short answer is...after the split, the same neutral wire is no longer the return path for two seperate phases. At least it shouldn't be unless there is a wiring error. If you open the neutral after the split, anything downstream will just go dead with no overvoltage danger.

It is the outlets after the open neutral but before the split that causes the problems. Devices plugged into these outlets will backfeed the voltage from both phases onto the neutral back to the point where it has been accidently opened. It can now overvoltage/undervoltage beyond the split and the devices plugged into those outlets can contribute to the problem as well.
 
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