only paralleling the neutral

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trekkie76

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I have seen an installation that doesn't look right, but I can not find anywhere in the code that prohibits it. The situation is this: 200A 3 phase panel, (1) 3/0 Cu to each phase, (2) 3/0 Cu to the neutral. I am just wondering if this neutral setup is acceptable, and if not where is it in the code book?
Thanks,
Gary
 
There is nothing in the NEC to prohibit parallelling the neutral in the way you described.

It has become more common for oversized neutrals to be installed for panels that have a high amount of non-linear loads.

Chris
 
It's done all of time and is typically noted as a 200% neutral. Also it seems that some engineers like to spec a 100 amp feeder/200% neutral with 5-#3 conductors. The #3's are not permitted in parallel since they're smaller than #1/0.
 
infinity said:
It's done all of time and is typically noted as a 200% neutral. Also it seems that some engineers like to spec a 100 amp feeder/200% neutral with 5-#3 conductors. The #3's are not permitted in parallel since they're smaller than #1/0.
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That's because it's easier to say "two" than figure which conductor size is twice the ampacity.
 
infinity said:
It's done all of time and is typically noted as a 200% neutral. Also it seems that some engineers like to spec a 100 amp feeder/200% neutral with 5-#3 conductors. The #3's are not permitted in parallel since they're smaller than #1/0.
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Rob, Neutral conductors size 2 AWG and larger can be ran in parallel on existing installations

under Engineering supervision. 310.4(A)(ex.2)
 
Thank you gentlemen for all of your answers. I had thought of the oversized neutral due to the Wye and possible non linear loads, I was just shown a picture with no info. and asked if this was legal. Just never seen it done that way, and anything different is usually scrutinized. Thanks again.

Gary
 
buddhakii said:
When running parallel neutrals for non-linear loads, do you have to count each as a ccc?
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I always do.

310.15(2) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a). Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.
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If it weren't considered a CCC why would you need an extra neutral in the first place? :smile:
 
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