2011 nec code question

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Mark Patterson

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I just went to a 2011 code update class and they were taling about having too run 3 nuetrals with a eq. ground when we have working with 208 three phase instead of just running 1 neutral with every three phases of the 208. Is this right.
 
A new section was added to Article 200.
2011 NEC
Article 200 Use and Identification of Grounded Conductors
200.4 Neutral Conductors. Neutral conductors shall not be used for more than one branch circuit, for more than one multiwire branch circuit, or for more than one set of ungrounded feeder conductors unless specifically permitted elsewhere in this Code.
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I read this to say one neutral conductor for all of the energized conductors in a multiwire circuit.
 
I read this as saying that a multiwire branch circuit (120/208V single phase or 208V three phase, for example) can still be served by a single neutral (if the neutral is required at all).

Moreover if a 215.4 or 225.7 permit the use of shared neutrals it would still be okay in that situation.

I think this is trying to eliminate the use of a shared neutral between 3 120V receptacle (non-linear) circuits because the neutral is not overcurrent protected.
 
I think the idea is to make sure that two ungrounded circuits from the same phase do not share a neutral.
 
charlie b said:
I think the idea is to make sure that two ungrounded circuits from the same phase do not share a neutral.
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I agree with charlie. Often times people change a panel and use the old panel as a splice box oversizing the neutral for many MWBC. This is not allowed One neutral per MWBC.
 
al hildenbrand said:
I read this to say one neutral conductor for all of the energized conductors in a multiwire circuit.
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Think of it as saying "No more than one conductor from each phase shall share a neutral."

If each line conductor has its own neutral (excuse me; grounded conductor), it is not a MWBC anyway.
 
LarryFine said:
If each line conductor has its own neutral (excuse me; grounded conductor), it is not a MWBC anyway.
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And if two or more ungrounded conductors of the same phase share a neutral, it is also not a MWBC. That has always been true, and I think the new code wording makes it even more clear that that is not allowed.
 
I did write it, but what I wrote is not exactly what ended up in the code.

That being said it is intended to prevent the use of an grounded conductor with two or more ungrounded conductors that do not have potential between them.

That was also my definition of "common neutral" that they rejected. The term common neutral was used in two code articles prior to the 2011 code and is now in three. It is my opinion that the term should be defined in Article 100.
 
Is there any requirement that circuit breakers for MWBC be adjacent prior to the requirement of handle ties?

I have seen breakers on different phases used that were not adjacent for MWBC.
 
tkb said:
Is there any requirement that circuit breakers for MWBC be adjacent prior to the requirement of handle ties?

I have seen breakers on different phases used that were not adjacent for MWBC.
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No, and I never hesitated to do that before the changes.
 
jumper said:
My point was that certain MWBCs before the 2008 code were required to be adjacent and handle tied/multi-pole pole breaker.
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Yes, you're right. Same yoke, and furniture partitions requirements have been around for a while. I believe that the furniture partition requirement goes back to the 2002 or 2005 NEC. But like Bob said, before the 2008 requirement it was quite common to use any two or three breakers for a MWBC even if they weren't adjacent to each other in the panel.
 
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