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#196980 - 11/03/10 05:29 PM Mixed cables and conductors in a raceway?  
gfretwell  Online Content


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Joined: Jul 2004
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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.


Greg Fretwell

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#196981 - 11/03/10 08:00 PM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]  
HotLine1  Offline


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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?



John

#196982 - 11/03/10 08:34 PM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]  
Niko  Offline
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Campbell, CA
can you install NM cable in a complete raceway system? Or only in a piece of raceway just for physical protection?


Be kind to your neighbor, he knows where you live


#196987 - 11/03/10 09:58 PM Re: Mixed cables and conductors in a raceway? [Re: Niko]  
gfretwell  Online Content


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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.


Greg Fretwell

#196994 - 11/04/10 02:37 PM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]  
Tesla  Offline
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Joined: Jun 2004
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Sacramento, CA
It's not a violation.

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

It's generally impractical.


Tesla

#196996 - 11/04/10 03:09 PM Re: Mixed cables and conductors in a raceway? [Re: Tesla]  
KJay  Offline
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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.


#197000 - 11/04/10 06:26 PM Re: Mixed cables and conductors in a raceway? [Re: KJay]  
gfretwell  Online Content


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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.


Greg Fretwell

#197002 - 11/04/10 07:28 PM Re: Mixed cables and conductors in a raceway? [Re: gfretwell]  
KJay  Offline
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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.


#197004 - 11/04/10 07:46 PM Re: Mixed cables and conductors in a raceway? [Re: KJay]  
HotLine1  Offline


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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.



John

#197030 - 11/05/10 09:40 PM Re: Mixed cables and conductors in a raceway? [Re: HotLine1]  
KJay  Offline
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Joined: Nov 2007
Posts: 763
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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