We were working at a factory installing 120V circuits for receptacles. While we were there we noticed that one of thier ex-plant electricians had done the same in the past only he used (1) #8 Thhn conductor as a neutral for (4) 120V circuits from a 120/240V single phase panel. There were two circuits on each phase. I know that this is not right but I can't think of any specific code section that this violates, other than the JB is overfilled. So, can anyone tell me which section(s) this violates?
There was much talk a couple years ago regarding computer and electronic loads. The talk that I heard indicated using a larger neutral. I have not heard much about it lately, but it is possible that is what the ex-electrician had in mind when installing the #8?
I agree that there might not be anything specifically prohibiting the practice but I would think that if it were allowed that there should be some method of calculating the size of the neutral conductor as well as some rule pertaining to handle ties on breakers. I believe there is a change regarding handle ties in the 2008 code. (210.4(B)) What is the definition of a "Multiwire Branch Circuit"?
CMP 2 does not agree that the NEC would permit the use of this common (super) neutral. text shown in italics below was to be deleted in my proposal
2-280 Log #2224 NEC-P02 Final Action: Reject (215.4) ______________________________________________________________ Submitter: Donald A. Ganiere, Ottawa, IL Recommendation: Revise as follows: 215.4 Feeders with Common Neutral. (A) Feeders with common Neutral Two or three sets of 3-wire feeders or two sets of 4-wire or 5-wire feeders shall be permitted to utilize a common neutral. (B) In Metal Raceway or Enclosure. Where installed in a metal raceway or other metal enclosure, all conductors of all feeders using a common neutral shall be enclosed within the same raceway or other enclosure as required in 300.20. Substantiation: There is no code violation in using a common neutral so the specific provision to use one is not required. Panel Meeting Action: Reject Panel Statement: The panel disagrees with the submitter’s substantiation. Section 215.4 (A) is the requirement which limits the number of feeders that may share a common neutral. Number Eligible to Vote: 12 Ballot Results: Affirmative: 12