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-   -   Use of unsheathed Romex NM-B wires in conduit? (http://www.diychatroom.com/f18/use-unsheathed-romex-nm-b-wires-conduit-28961/)

WoodworkerDave 09-29-2008 11:24 AM

Use of unsheathed Romex NM-B wires in conduit?
 
Quick question:

I need to drop three circuits down a concrete basement wall to two adjacent 4 x 4 receptacle boxes I'll be mounting on the wall. I want to protect the wires along the wall within one run of 3/4" EMT. Can I just bring the NM-B cables into a junction box mounted near the ceiling and strip off 4-5 feet of sheathing from these cables and drop the individual wires through the conduit to the boxes?

Fill restrictions prevent me from running the whole NM cables within the conduit. Basically, I want to know if I can avoid having to splice in actual THHN/THWN wire at the junction box for the drop through the conduit (the wires within the Romex cable are not marked as to their specifications). I'll use a separate insulated green ground wire through the conduit, so I can splice all the grounds together in the junction box and just run one ground wire to the boxes.

Thanks for your help.

joed 09-29-2008 11:52 AM

Idividual wires in NM-B are not rated for conduit use.

Termite 09-29-2008 12:00 PM

Agreed. No can do. :no:

WoodworkerDave 09-29-2008 12:10 PM

Thanks. I'll be buying some THHN/THWN wires for the drop.

Stubbie 09-29-2008 12:23 PM

Conduit fill requirements do not apply to short lengths of conduit that are not emerging from grade and the conduit is only being used for physical protection. See note 2 chapter nine.

WoodworkerDave 09-29-2008 01:54 PM

Thanks Stubbie. I guess I forgot about that note when I first read it a while back. So this means I can put a suitable cable clamp at the top of the conduit and run the 3 NM cables directly down to the outlet boxes. This will be so much easier. Thanks again.

Stubbie 09-29-2008 02:09 PM

Yep. alot of guys just put on a emt box connector and then thread on a plastic bushing to handle any abrasion issue where the cables enter emt. I actually think it is a code requirement to do so.


Two types I use

http://tbn0.google.com/images?q=tbn:...0%2520EXMP.jpg
and
http://tbn0.google.com/images?q=tbn:...ed_bushing.jpgwith this....
http://tbn0.google.com/images?q=tbn:..._connector.jpg

Termite 09-29-2008 04:17 PM

Quote:

Originally Posted by Stubbie (Post 166373)
Yep. alot of guys just put on a emt box connector and then thread on a plastic bushing to handle any abrasion issue where the cables enter emt. I actually think it is a code requirement to do so.


Two types I use

http://tbn0.google.com/images?q=tbn:...0%2520EXMP.jpg
and
http://tbn0.google.com/images?q=tbn:...ed_bushing.jpgwith this....
http://tbn0.google.com/images?q=tbn:..._connector.jpg

A bushing is a code requirement for protection of the wire. I use the cheapo plastic ones.

Sorry, I failed to thoroughly read the original post that said that this was a very short length of conduit indoors...My bad. Glad Stubbie got to you before you bought the THHN. :whistling2:

chris75 09-29-2008 06:21 PM

Quote:

Originally Posted by thekctermite (Post 166416)

Sorry, I failed to thoroughly read the original post that said that this was a very short length of conduit indoors... :whistling2:


Who cares if its a short run, you can still use NM in conduit as long as the fill requirement is met.


Never mind, I agree with Stubbie. :)

joed 09-29-2008 06:47 PM

I don't think you will fit 3 NM cables into a 3/4 conduit.

chris75 09-29-2008 06:57 PM

Quote:

Originally Posted by joed (Post 166476)
I don't think you will fit 3 NM cables into a 3/4 conduit.

Sure you will, 3/4 is huge.


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