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#196980 - 11/03/10 02:29 PM Mixed cables and conductors in a raceway?
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
Is there a violation if you used a cable with another conductor or two in a raceway system?
(example a 12-3 w/g Romex and an additional THHN for the 4th ungrounded conductor in a 3/4" raceway).
It didn't sound right when I heard it but I am not sure what you would cite.
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#196981 - 11/03/10 05:00 PM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
That's interesting...
I must say none of the rocket scientists here thought that up....yet!
Time to ponder what (if anything) to cite.

FYI: another reason to add common sense to the NEC?
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#196982 - 11/03/10 05:34 PM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]
Niko Offline
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Registered: 08/17/06
Posts: 358
Loc: Campbell, CA
can you install NM cable in a complete raceway system? Or only in a piece of raceway just for physical protection?
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#196987 - 11/03/10 06:58 PM Re: Mixed cables and conductors in a raceway? [Re: Niko]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
I can't cite any rule that says you can't have NM cable in a raceway system. Since all circuit conductors come through the same connector there are no inductive heating problems. I know this is ugly but I am stumped to come up with a violation.
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Greg Fretwell

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#196994 - 11/04/10 11:37 AM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]
Tesla Offline
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Registered: 06/16/04
Posts: 1280
Loc: Sacramento, CA
It's not a violation.

However, due to economics you'd not expect to see it.

It's generally impractical.
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Tesla

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#196996 - 11/04/10 12:09 PM Re: Mixed cables and conductors in a raceway? [Re: Tesla]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
Iím wondering if 300.3[B] and 300.3[B],1 might apply if the conductors are all part of the same circuit, since both also state the same "cable or cord" as well.
Something else maybe, is that 334.15[B] is for exposed work, so not sure if this would preclude the NM from being run in a conduit that is concealed or partially concealed.

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#197000 - 11/04/10 03:26 PM Re: Mixed cables and conductors in a raceway? [Re: KJay]
gfretwell Offline

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Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
I suspect the RX was there first and the THHN was added.

KJay, this was all exposed in a garage/shop. A 240 2 pole was converted to 120/240 3 pole from what I could assume.
I see RX in pipe quite a bit, just because that is what resi guys have on the truck or what homeowners buy at the HD. I bet 99% of it is fed into the pipe as they build the system just because of how hard it is to pull RX in pipe.
I think part of it is you can buy RX cheaper than THHN if you don't want 500 feet.

I was not AHJ, just asked if it was legal as "gee whiz" info.
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#197002 - 11/04/10 04:28 PM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
I guess technically you might be able to say that EMT fittings are not designed or listed for use with NM cables, since I see where 300.15 says that fittings and connectors shall be used only with the specific wiring method for which they are designed and listed.

IMO, I donít think the NEC allowing NM to be sleeved for protection was intended to allow unlimited use like that, but Iím also not sure exactly where to find a specific rule prohibiting it.

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#197004 - 11/04/10 04:46 PM Re: Mixed cables and conductors in a raceway? [Re: KJay]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
Kjay:
The fittings you reference above are EMT, and used on the EMT, not the NM as I understand Gregs description. 300.15 would be a bad cite.

I tend to say there is nothing to directly cite, unless at the begining of the circuit, there is no 'from-to' connector.
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#197030 - 11/05/10 06:40 PM Re: Mixed cables and conductors in a raceway? [Re: HotLine1]
KJay Offline
Member

Registered: 11/27/07
Posts: 763
Loc: MA, USA
Originally Posted By: HotLine1
Kjay:
The fittings you reference above are EMT, and used on the EMT, not the NM as I understand Gregs description. 300.15 would be a bad cite.

I tend to say there is nothing to directly cite, unless at the begining of the circuit, there is no 'from-to' connector.



True. It was just something to mull over. My thought was that NM is a separate wiring method with its own installation requirements and listed connectors, etc.

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