Parallel Neutrals

[GoldDigger]

That's what I would have thought. But then I look at 310.10(H)(2) and I see the specific inclusion of EGCs. Granted, they are not included in 310.10(H)(1). It's confusing.

And as far as non-current carrying conductors, I certainly don't see an exception for MWBC neutrals.

May be some work for the CMP if a proposal is submitted about it. Also the question (as in loop circuits in UK practice) of whether two conductors can create a parallel path without being in parallel. (Does "joined electrically at both ends" include when at each end they both connect to different things which are joined somewhere else, for example.)

 

[Dennis Alwon]

May be some work for the CMP if a proposal is submitted about it. Also the question (as in loop circuits in UK practice) of whether two conductors can create a parallel path without being in parallel. (Does "joined electrically at both ends" include when at each end they both connect to different things which are joined somewhere else, for example.)

That is an age old question but IMO that is a parallel neutral. Also called a loop circuit however current will travel in both directions which IMO, is not a good thing.

 

[petersonra]

I have been known to run ring circuits to reduce voltage drop on 5VDC supplies.

 

[don_resqcapt19]

.... Also called a loop circuit however current will travel in both directions which IMO, is not a good thing.

Why is that not a "good thing"? It reduces voltage drop and increases reliability. If the ampacity of the wire is equal to or greater than the rating of the OCPD, I don't see any issues other than the code rule.

 

[DBoone]

I understand the issue but if you take the 2- 12/2 nm cables in box 1 and tie them through then the 3 way is a dead end. Neutral is there so just tie everything together in Box 2.

Is this thread more about why it can't be done the way it is? The biggest objection I see to the install as the OP has it is that you have created electromagnetic field's that one probably doesn't want. I agree it is a code violation.

Are there no EMFs with conductors that are 1/0 or larger?

 

[Dennis Alwon]

Are there no EMFs with conductors that are 1/0 or larger?

With a standard parallel connection the installation is different. Both neutrals travel the same path. In this install you have neutrals travelling different paths so the current can travel both paths.

 

[BPoindexter]

I remember reading something on this a long time ago. If I remember correctly it has to do with the resistance per foot of the conductor. The smaller gauges have much higher resistance per foot of conductor than the larger sizes. With a routing/length difference the differential current on the paralleled conductors would be much higher on the smaller wire. I will see if I can dig up the source. If I remember correctly 1/0 was selected based on some determination of acceptability vs likelihood of install issues, after all you will rarely have the exact length on all of the conductors. But that was long ago in a galaxy far away and my memory may be tricking me....

In this case where both neutrals are sufficiently sized for the breaker I do not see an actual safety issue that I would lose sleep over. But it would be a violation of 310.4 and by the way EGC's are covered in 310.4(E):

(E) Equipment Grounding Conductors. Where parallel
equipment grounding conductors are used, they shall be
sized in accordance with 250.122. Sectioned equipment
grounding conductors smaller than 1/0 AWG shall be permitted
in multiconductor cables in accordance with 310.13,
provided the combined circular mil area in each cable complies
with 250.122.