Sharing Neutrals

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JFletcher said:
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Going by the NEC, two or more hots on the same phase sharing a neutral would be parallel conductors and a violation in the case of 15 or 20A circuits.
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infinity said:
How would the circuits be connected at both ends?
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Fletch is on the wrong track, so I'll help y'all out. Two violations...
200.4 Neutral Conductors. Neutral conductors shall be
installed in accordance with 200.4(A) and (B).

(A) Installation. 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.

(B) Multiple Circuits. Where more than one neutral conductor
associated with different circuits is in an enclosure,
grounded circuit conductors of each circuit shall be identified
or grouped to correspond with the ungrounded circuit
conductor(s) by wire markers, cable ties, or similar means
in at least one location within the enclosure.

Exception No. 1: The requirement for grouping or identifying
shall not apply if the branch-circuit or feeder conductors
enter from a cable or a raceway unique to the circuit
that makes the grouping obvious.

Exception No. 2: The requirement for grouping or identifying
shall not apply where branch-circuit conductors pass
though a box or conduit body without a loop as described
in 314.16(B)(1) or without a splice or termination.
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...and...

240.8 Fuses or Circuit Breakers in Parallel. Fuses and
circuit breakers shall be permitted to be connected in parallel
where they are factory assembled in parallel and listed
as a unit. Individual fuses, circuit breakers, or combinations
thereof shall not otherwise be connected in parallel.
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Smart $ said:
Fletch is on the wrong track, so I'll help y'all out. Two violations...


...and...
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*sobs*

But really, someone tell me where a #12 connected to A phase, say #1 breaker, and another connected to #4 breaker (same A, in 3ph) or #5 breaker (split/single phase) can share a #10 neutral. or any neutral. I may have cited the wrong code, however one cannot run multiple #12s/#14s from a single leg and use one neutral. To suggest the OP's quote was aiming at such is preposterous imo; it's clearly talking about MWBC.
 
JFletcher said:
*sobs*

But really, someone tell me where a #12 connected to A phase, say #1 breaker, and another connected to #4 breaker (same A, in 3ph) or #5 breaker (split/single phase) can share a #10 neutral. or any neutral. I may have cited the wrong code, however one cannot run multiple #12s/#14s from a single leg and use one neutral. To suggest the OP's quote was aiming at such is preposterous imo; it's clearly talking about MWBC.
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I quoted and highlighted the section above: "Neutral conductors shall not be used for more than one branch circuit, ..." from 200.4(A).

If the spec' is referring to a MWBC, then just write MWBC.
10. All 15- and 20A MWBC's shall use a #10 AWG THHN copper neutral.
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infinity said:
How would the circuits be connected at both ends?
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For argument's sake, let's suppose a lighting load with emergency battery backup. Miswire creates a connection at ballast end, as well as the panel. Even if the ballast and emergency ballast were wired same phase, any cross connection would be a parallel conductor setup, or did the NEC ditch paralleling <#1 CU between 2008 and 2014 (2017)?
 
Smart $ said:
I quoted and highlighted the section above: "Neutral conductors shall not be used for more than one branch circuit, ..." from 200.4(A).

If the spec' is referring to a MWBC, then just write MWBC.
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I saw your post. Im just trying to figure out how two hots on the same phase of a 15 or 20A circuit can share a neutral. Your quote is correct; I think there is another code section that prohibits this.
 
JFletcher said:
*sobs*

But really, someone tell me where a #12 connected to A phase, say #1 breaker, and another connected to #4 breaker (same A, in 3ph) or #5 breaker (split/single phase) can share a #10 neutral. or any neutral. I may have cited the wrong code, however one cannot run multiple #12s/#14s from a single leg and use one neutral. To suggest the OP's quote was aiming at such is preposterous imo; it's clearly talking about MWBC?
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By rights you can't, but a greenhorn that didn't know any different would win the argument if going by the whacko spec posted in post #1.

It's not clearly talking about a MWBC.

MWBC is not mentioned at all in that spec. So actually it's open to speculation.

Which is what we've been talking about all along.

Better had they of just used the phrase MWBC.

Better question would be,Why do we have to use a #10 neutral if using it for 15 or 20 amp MWBC's ?

JAP>
 
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JFletcher said:
I saw your post. Im just trying to figure out how two hots on the same phase of a 15 or 20A circuit can share a neutral. Your quote is correct; I think there is another code section that prohibits this.
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:? Must be trees in the way... :slaphead:
 
jap said:
By rights you can't, but a greenhorn that didn't know any different would win the argument if going by the whacko spec posted in post #1.
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If a greenhorn is running a job that is more of an issue than the spec

It's not clearly talking about a MWBC.
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Yes it is too anyone with experience and code knowledge.

MWBC is not mentioned at all in that spec. So actually it's open to speculation.
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Only to those who don't know electrical work.


Better question would be,Why do we have to use a #10 neutral if using it for 15 or 20 amp MWBC's ?
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Because the specs say so and the more the job costs the more money to be made.
 
jap said:
It's not clearly talking about a MWBC.

MWBC is not mentioned at all in that spec.
Better had they of just used the phrase MWBC.

Better question would be,Why do we have to use a #10 neutral if using it for 15 or 20 amp MWBC's ?

JAP>
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It seems clear as day to me as well as MrLucky and others. Oversized neutrals are nothing new when using MWBC's so the spec is fairly boilerplate. In MrLucky's situation they want a #10 neutral if there is a shared neutral with #12 ungrounded conductors.
 
JFletcher said:
*sobs*

But really, someone tell me where a #12 connected to A phase, say #1 breaker, and another connected to #4 breaker (same A, in 3ph) or #5 breaker (split/single phase) can share a #10 neutral. or any neutral. I may have cited the wrong code, however one cannot run multiple #12s/#14s from a single leg and use one neutral. To suggest the OP's quote was aiming at such is preposterous imo; it's clearly talking about MWBC.
Click to expand...

Ok since I started this great dialogue..lol..can someone help me out this be able able to identify a,b and c phases in panels as fletch mentions above. Going down left hand side of panel with beakers 1,3,5,7 etc. starting with circuit 1....is that phase A? Then circuit 3 is phase B then 5 is C then 7 A etc.?

starting on right side of panel would 2 be A and so on? Thanks
 
infinity said:
It seems clear as day to me as well as MrLucky and others. Oversized neutrals are nothing new when using MWBC's so the spec is fairly boilerplate. In MrLucky's situation they want a #10 neutral if there is a shared neutral with #12 ungrounded conductors.
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That was exactly my though but always like to get the " pros/experts" opinion if I'm unsure.
 
So what I get from reading all this and those saying the spec can be left up to interpretation boils down to the spec not being clear as to the circuits being on DIFFERENT or SAME phases and ungrounded/hot conductors on the same phase would NOT be a MWBC? Correct?
 
mstrlucky74 said:
Ok since I started this great dialogue..lol..can someone help me out this be able able to identify a,b and c phases in panels as fletch mentions above. Going down left hand side of panel with beakers 1,3,5,7 etc. starting with circuit 1....is that phase A? Then circuit 3 is phase B then 5 is C then 7 A etc.?

starting on right side of panel would 2 be A and so on? Thanks
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As far as I know there are no standard rules for the numbering

However there are rules for phase arrangement ABC top to bottom, left to right.

So in most cases panels are numbered with the odd numbers on the left and the even numbers on the right.


1 - A - 2

3 - B - 4

5 - C - 6

7 - A - 8


Repeated as many times as needed.
 
mstrlucky74 said:
So what I get from reading all this and those saying the spec can be left up to interpretation boils down to the spec not being clear as to the circuits being on DIFFERENT or SAME phases and ungrounded/hot conductors on the same phase would NOT be a MWBC? Correct?
Click to expand...

The only way to read the spec and determine they mean the same phases is to ignore the NEC rules prohibiting that.

Even if the person writing the spec means the same phase you cannot install it that way.
 
mstrlucky74 said:
So what I get from reading all this and those saying the spec can be left up to interpretation boils down to the spec not being clear as to the circuits being on DIFFERENT or SAME phases and ungrounded/hot conductors on the same phase would NOT be a MWBC? Correct?
Click to expand...

It says two or three phases not the same phase.
 
mstrlucky74 said:
So what I get from reading all this and those saying the spec can be left up to interpretation boils down to the spec not being clear as to the circuits being on DIFFERENT or SAME phases and ungrounded/hot conductors on the same phase would NOT be a MWBC? Correct?
Click to expand...

It was just some very smart people here devolving in to, as Smart$ put it, a pedantic discussion. They didn't step back to realize that it isn't helpful to a less scholarly electrician. When you consider that the NEC itself is filled with unclear instruction it is rather picky to make this oversight by an engineer out to be such a huge faux paus. Not only would conductors on the same phase not be MWBC's it is a fundamental aspect of being an electrician that you can't share a neutral on two conductors of the same phase. If any commercial job I was overseeing had that happen, I would blame the foreman, because no one that doesn't know this tidbit should be allowed to land a wire anyway.
 
iwire said:
The only way to read the spec and determine they mean the same phases is to ignore the NEC rules prohibiting that.

Even if the person writing the spec means the same phase you cannot install it that way.
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Thanks and understood. Seems like an easy decision.
 
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