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#184402 - 02/09/09 02:10 PM NM Protection - Exposed Work
InspectorE Offline

Registered: 10/08/04
Posts: 51
Loc: Hudson WI USA
Section 334.16(b)requires that NM used in exposed areas be protected with conduit or other approved means. Does the code indicate minimum diameters for various NM sizes similar to the conduit fill tables? Or is the amount of space taken up by the NM irrelevant with respect to conduit diameter? If so is it left to the installer's judgement?

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#184403 - 02/09/09 02:11 PM Re: NM Protection - Exposed Work [Re: InspectorE]
InspectorE Offline

Registered: 10/08/04
Posts: 51
Loc: Hudson WI USA
That should be 334.15(b), not 16..typo

#184405 - 02/09/09 02:43 PM Re: NM Protection - Exposed Work [Re: InspectorE]
gfretwell Offline


Registered: 07/20/04
Posts: 9026
Loc: Estero,Fl,usa
You use the circular size defined by the widest dimension of the cable. For flat Romex that makes a pretty fat "conductor". A 12-2 is about .4" which puts it between a #2 and a #1 THHN. Generally I will make some concession if this is a single straight run down a wall.
Greg Fretwell

#184409 - 02/09/09 04:07 PM Re: NM Protection - Exposed Work [Re: gfretwell]
LK Offline


Registered: 01/21/03
Posts: 1721
Loc: New Jersey
Yup, it's all spelled out in the code.


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