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Super Neutral #173333 01/07/08 08:35 PM
Joined: Apr 2002
Posts: 257
M
master66 Offline OP
Member
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?

Brian

Work Gear for Electricians and the Trades
Re: Super Neutral [Re: master66] #173334 01/07/08 08:46 PM
Joined: Dec 2000
Posts: 4,287
electure Offline
Member
No code has been violated if he has 2ea 20 amp circuits on each leg.

Re: Super Neutral [Re: electure] #173336 01/07/08 09:05 PM
Joined: May 2002
Posts: 1,716
R
Roger Offline
Member
Brian, I agree with Electure, no code has been violated, and it is specifically allowed in 225.7(B)

Roger

Re: Super Neutral [Re: Roger] #173342 01/07/08 10:39 PM
Joined: Apr 2002
Posts: 257
M
master66 Offline OP
Member
Section 225.7(B) Applies to "Lighting Equipment Installed Outdoors". Is there a similar section regarding 120V receptacles?

Re: Super Neutral [Re: master66] #173408 01/09/08 10:55 AM
Joined: Jun 2007
Posts: 301
J
JValdes Offline
Member
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?

Re: Super Neutral [Re: master66] #173411 01/09/08 11:57 AM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
I also agree there is no violation and no safety hazard.

Originally Posted by master66
Section 225.7(B) Applies to "Lighting Equipment Installed Outdoors". Is there a similar section regarding 120V receptacles?


The real question is where does the code prohibit what was done?

It does not. smile


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: Super Neutral [Re: master66] #173435 01/09/08 08:24 PM
Joined: Apr 2002
Posts: 257
M
master66 Offline OP
Member
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"?

Brian

Re: Super Neutral [Re: master66] #173439 01/09/08 09:10 PM
Joined: May 2007
Posts: 47
B
BryanInBalt Offline
Member
Originally Posted by master66
there should be some method of calculating the size of the neutral conductor Brian


The 12 wire should be adequate for the load wink
(cheap shot I know)

I think everyone is just site engineering these as they go along but when I've done it we used a #10 with 3 #12 hot.

But it may all be moot anyway since paired MC is being used in most jobs now anyway.

Right from the panel no conduit on the job at all. awful.


Design-Build isn't supposed to mean design *as* you build.
Re: Super Neutral [Re: BryanInBalt] #173440 01/09/08 09:24 PM
Joined: Nov 2000
Posts: 2,148
R
resqcapt19 Offline
Member
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
Quote
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


Don(resqcapt19)
Re: Super Neutral [Re: resqcapt19] #173441 01/09/08 09:29 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Originally Posted by resqcapt19
CMP 2 does not agree that the NEC would permit the use of this common (super) neutral.


I guess if the CMPs handed out red tags they would also have to provide a code section that this installation violates. smile


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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