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#89553 - 10/02/04 06:00 PM All conductors run together ?
Jim M Offline

Registered: 08/10/01
Posts: 453
Loc: Chestertown, MD, USA
This was posted on a DIY site.

I have not read the quoted sections to see the differences.

Was this an oversight by the CMP's?

I know that this "all conductors run together" statement has been made many times, often even by me. But I am now going to begin the long tedious process of correcting this myth. It used to be true, but since the 1999 code, it no longer is. All conductors only need be run together if run in metal conduit or into metal boxes. If you are using NM-B cable and plastic boxes, and if your area is using the 1999 or 2002 NEC, then all conductors do not need to be run together.

For anyone wishing to research this further, please check out the differences in Article 300.3(B) between the 1996 and 1999 codes.

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#89554 - 10/03/04 04:11 AM Re: All conductors run together ?
iwire Offline

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
2002 NEC 300.3(B)
300.3(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 conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (4).

300.3(B)(3) Nonferrous Wiring Methods. Conductors in wiring methods with a nonmetallic or other nonmagnetic sheath, where run in different raceways, auxiliary gutters, cable trays, trenches, cables, or cords, shall comply with the provisions of 300.20(B). Conductors in single-conductor Type MI cable with a nonmagnetic sheath shall comply with the provisions of 332.31. Conductors of single-conductor–type MC cable with a nonmagnetic sheath shall comply with the provisions of 330.31, 330.116, and 300.20(B).

So they are correct if you follow the rules of 300.3(B)(3) and 300.20(B) you may run the conductors of a circuit separately.

You could run the 'hot' from the panel to a switch and the neutral from the panel to a light.

Why you would want to do this I have no idea unless you are running K & T.
Bob Badger
Construction & Maintenance Electrician

#89555 - 10/03/04 06:06 AM Re: All conductors run together ?
winnie Offline

Registered: 09/15/03
Posts: 652
Loc: boston, ma
The only 'good' reason that one might want to do this is in a situation where you need more than 2 phase conductors and are limited to common ga-2 or ga-3 NM cable assemblies.

Not introducing large current loops is IMHO a good thing, but I don't see a significant problem with two NM cables running side by side, with the neutral in one cable and the corresponding phase conductors in the other.


#89556 - 10/03/04 08:17 PM Re: All conductors run together ?
SolarPowered Offline

Registered: 07/05/04
Posts: 615
Loc: Palo Alto, CA, USA
I think I may have seen the discussion to which Jim is referring, or, at least, a similar one. Situation was for a combination bathroom fixture, with, as I remember, a light, a fan, and a heater. Power first went to the three-gang switch. The GC had screwed up before closing up the walls, and was trying to get the homeowner to go for running 2 12/2's, one with the hot and one of the switched legs, the other with other two switched legs.

I pretty much said, "No way in hell!" About ten posts later, someone came up with abovementioned references. I don't remember how it finally came out. It looks to me like it probably meets the letter of the Code, but I still think it's wrong, wrong, wrong!


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