ECN Forum Forums Code Related Discussion NEC & other Code issues New panel/gutter question

I belive that there is only implication that this is not allowed, but no actual code to back it up.

The physics certainly works.

Bob pointed out the explicitly permission for a common neutral in 225.7 for _lighting_ equipment installed _outdoors_.

215.4 explicitly permits feeders with common neutral. You are explicitly permitted to install 6 ungrounded conductors (for 2 separate three phase feeds) with a _single_ suitably sized common neutral. If I read this correctly (and I've not delved too deeply), I don't even see a requirement that these feeders originate from the same panelboard or even the same system. Imagine the possibilities for ugliness

210.4 permits multiwire branch circuits, and article 100 has a definition (Branch Circuit, Multiwire) which specifies that the ungrounded conductors in a multiwire branch circuit have a voltage between them.

300.3 has explicit permission for the shared neutral bus in a gutter attached to the panelboard.

One could argue that the lack of explicit permission for common neutral branch circuits in article 210 implies that they are not permitted,...but IMHO this is a rather weak argument that would not stand up legally. It most this lack of explicit permission or prohibition suggests that this is an extremely uncommon practise.

-Jon

Winnie- I agree with you. I have read this post over a coupla times and I have been enlightened by your response and Bob's. I don't see this as a routine installation and all it really amounts to is an extention of the neutral bus. If I were to inspect this type of installation I would be asking for some calculations, you can bet your bippy on that. See, Inspectors are human (some of them)

George if you ever do see this installation let us know.

I have never seen it and can not think of a way to pull it off for less money than the standard wiring methods.

By the time you use boxes with enough CI and buy connectors to terminate the large common neutral I think you will have spent much more money.

Bob

If you have the Feeder, and all the branches running through the gutter. (For other reasons, like accomadating entrance to the panel anyway.) Why not just pull the nuetral bar from the panel and re-locate it in the gutter. For Resi AFCI's, or GFI breakers that would require a neutral connection in the panel, I guess it would not work...

As for codes to back it up, does this work?


FYI: I do this with Grounds all the time... Terminate them and bond accordingly to the panel ground with a single conductor. Not neutrals, but if allowed I might start to rethink of doing it for them too.

[This message has been edited by e57 (edited 11-06-2005).]

As Bob said, we've been here before.

Is it a violation wired this way?