One large neutral carried to a second location

Status
Not open for further replies.
P

poopdeckpappy

Member
Location
Franklin, LA
Remodel project where all raceways and boxes are bricked in, making substantial modifications unappealing.

New surface mounted load center being installed and connected to several existing boxes in the wall to which all existing raceways connect. Considering a wireway to connect the new load center to the old boxes.

Supposing that the conductor fill in the wireway and existing boxes will be OK, does anyone see a violation pulling one appropriately sized neutral conductor from the load center to an existing box along with the branch circuit protected L1, L2 & L3 conductors and installing a listed neutral bar in the existing boxes to serve as the point of connection.

One large neutral goes a long way in keeping conductor count below 30 to keep from having to derate.

Why not just use sub panels at the different locations, you ask? Insufficient working space.
 
Have you asked this question of a local EC or electrician?
It would seem to me that the proposed installation would violate the requirement that the branch circuit neutral conductors originate at the same panelboard as the ungrounded conductors. Having them originate in the intermediate box would not satisfy that.
A second requirement is that all circuit conductors, grounded as well as ungrounded, must travel in the same raceway.

And finally, your proposal would be unsafe since working on the shared neutral would require deenergizing all of the associated branch circuits and I do not see a good way to document that.
 
:happyno:

200.4(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
 
Branch circuit neutrals would still originate at the same panelboard as the ungrounded conductors. I interpret your citation as intending to prevent neutrals from separate panelboards from being treated interchangeably throughout a facility.

Second point, where would they not travel in the same raceway?

Edited, found this posted elsewhere from a 2002 NEC handbook which illustrates my original question more clearly..

commonneutral.JPG
 
Last edited:
poopdeckpappy said:
Branch circuit neutrals would still originate at the same panelboard as the ungrounded conductors. I interpret your citation as intending to prevent neutrals from separate panelboards from being treated interchangeably throughout a facility.

Second point, where would they not travel in the same raceway?
Click to expand...

I just reread your first post.

Are you just trying to consolidate single branch circuits from a common panel into multiwire branch circuits with a shared neutral?

IE: 3 single 20A circuits with 3 x L-N-G, 6 CCC + 3 Gs into 1 20A MWBC with 3 L, 1N, 1 G, 3 CCCs + N +G. N may not be a CCC.
 
poopdeckpappy said:
Branch circuit neutrals would still originate at the same panelboard as the ungrounded conductors. I interpret your citation as intending to prevent neutrals from separate panelboards from being treated interchangeably throughout a facility.

Second point, where would they not travel in the same raceway?

Edited, found this posted elsewhere from a 2002 NEC handbook which illustrates my original question more clearly..

View attachment 16999
Click to expand...

That picture is specific to 225.7(B) A common neutral for outdoor lighting. It would not be legal for general building premise wiring.
 
poopdeckpappy said:
Not constructing multi wire branch circuits, think of it as extending the load center's neutral bus to a second location.
Click to expand...

:happyno: Not by itself you ain't.

300.3(B)(B) Conductors of the Same Circuit.
All conductors of the same circuit and, where used, the grounded conductor
and all equipment grounding conductors and bonding con-
ductors shall be contained within the same raceway, auxil-
iary gutter, cable tray, cablebus assembly, trench, cable, or
cord, unless otherwise permitted in accordance with
300.3(B)(1) through (B)(4)
 
poopdeckpappy said:
Not constructing multi wire branch circuits, think of it as extending the load center's neutral bus to a second location.
Click to expand...
And we are saying that the only (partial) solution available to you would be to take pairs of circuits and combine them, following NEC rules, into one MWBC per pair. You would not end up with a single neutral, but you would have half as many AND the individual MWBC neutrals would not be counted at all as Current Carrying Conductors for derating purposes. They would still count for raceway fill calculations.
 
jumper said:
That picture is specific to 225.7(B) A common neutral for outdoor lighting. It would not be legal for general building premise wiring.
Click to expand...

I've seen what the OP is describing before and was looking for a code section at the time the would dis allow it.
They had a 2" conduit coming out of a Panelboard to above the ceiling to a large J-box. An isoltated neutral bar was mounted inside the j-box and the 2" conduit had every bit of 20 ungrounded conductors and (1) 3/0 Neutral conductor run from the Panel to the Neutral bar located in the J-box in the 2" conduit.

All of the branch circuit neutrals landed on the Neutral Bar in the J-box and the single 3/0 neutral carried the neutral current back to the panel.

So is 300.3 the section that this violates?
What part of the wording in 300.3(b)(b) does what's described above violate?

JAP>
 
Never mind.

I think I see where its coming from.
The branch neutrals don't make it all the way back to the panel with the ungrounded conductors.
They stop short at the J-box.

JAP>
 
jap said:
Never mind.

I think I see where its coming from.
The branch neutrals don't make it all the way back to the panel with the ungrounded conductors.
They stop short at the J-box.

JAP>
Click to expand...

And under 30.33 the single large wire is a shared neutral.
There are other sections (no number reference) which I referred to also, but 300.33 is the strongest and most specific.
 
jumper said:
That picture is specific to 225.7(B) A common neutral for outdoor lighting. It would not be legal for general building premise wiring.
Click to expand...

Yes, it would be still allowed for conditions covered by 225.7(B). I think the confusion here is the OP is showing that diagram from the 2002 Handbook to show that this is OK to do in his application. It was allowed for his application under the 2002 edition. This was changed to prohibit his application in the 2011 edition.
 
Not being argumentative with the members who have responded thus far but in this case I will dig my heels in and say the NEC gets this one wrong.

"Home runs" of individual neutrals through 15ft of wireway is in no way superior to or safer than an extension of the neutral bus to a separate enclosure.

Different paths (raceways, wireways, boxes, conduits) aren't being taken so nothing is being obfuscated.

Speaking to sharing a neutral between too many circuits, the grounded conductor between X0 on the transformer and the load center is shared between all of the circuits in that panel. It works because it is sized correctly not because there is something special about it.
 
poopdeckpappy said:
Not being argumentative with the members who have responded thus far but in this case I will dig my heels in and say the NEC gets this one wrong.

"Home runs" of individual neutrals through 15ft of wireway is in no way superior to or safer than an extension of the neutral bus to a separate enclosure.

Different paths (raceways, wireways, boxes, conduits) aren't being taken so nothing is being obfuscated.

Speaking to sharing a neutral between too many circuits, the grounded conductor between X0 on the transformer and the load center is shared between all of the circuits in that panel. It works because it is sized correctly not because there is something special about it.
Click to expand...


I'd have to dig my heels in and strongly disagree.

Jap>
 
poopdeckpappy said:
Not being argumentative with the members who have responded thus far but in this case I will dig my heels in and say the NEC gets this one wrong.

"Home runs" of individual neutrals through 15ft of wireway is in no way superior to or safer than an extension of the neutral bus to a separate enclosure.

Different paths (raceways, wireways, boxes, conduits) aren't being taken so nothing is being obfuscated.

Speaking to sharing a neutral between too many circuits, the grounded conductor between X0 on the transformer and the load center is shared between all of the circuits in that panel. It works because it is sized correctly not because there is something special about it.
Click to expand...

The neutral to X0 on a transformer clearly cannot be worked on without de-energizing the transformer or everything connected to it (at the first OCPD).
The shared neutral of an MWBC is (per current code) clearly traceable inside the panel where it originates and the disconnect for the two sides of the circuit must either have a single handle or a handle tie, so that opening one side opens both.
The arrangement you propose could be clearly labelled in the panel of origin to indicate that it is the neutral for N breakers, and identify the list, but it would be uncommon enough to potentially pose a hazard to someone encountering it long after it was installed. It is not per se unsafe, but it is non-standard, which makes it somewhat risky regardless.

Bottom line is that the code forbids it. There are a lot of situations where reasonable people may see the code as overly restrictive, but it is what we have to follow.
 
poopdeckpappy said:
Not being argumentative with the members who have responded thus far but in this case I will dig my heels in and say the NEC gets this one wrong....
Click to expand...

I have my disagreements with the NEC too. I don't like following rules I don't agree with when I know I am right, but at the end of the day I know I don't want to be the one who is in charge of making all the rules.
 
Status
Not open for further replies.
Top