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#209231 03/17/13 03:24 PM
Joined: Mar 2005
Posts: 236
Member
Romex now has to be derated going though holes in wood structures? We are using the 2011 NEC here and I don't see any exceptions in the Washington Administrative Code(which supersedes NEC).

I didn't remember that when taking my continuing education class, but have recently gone to work for another contractor who has contracts for mixed use buildings that are stick built. We are using romex in the dwelling units so I thought I would read up(years since I used romex) and 334.80 directs you back to the conduit fill table.

Am I crazy or misinterpreting?
Thanks,
H20

2017 / 2014 NEC & Related Books and Study Guides
watersparkfalls #209232 03/17/13 03:49 PM
Joined: Jul 2004
Posts: 9,662
Likes: 4
G
Member
NFPA is crazy, you are reading it right.
They are really telling us we need to drill more holes. In reality you still have the practical limit of 9 current carrying conductors (using the 90c column) through one hole so it is not that restrictive.

I am still not sure why I don't have to derate until a nipple is 2 feet long, even if it is packed in foam but I have to derate in a 1.5" penetration with some foam in it.


Greg Fretwell
watersparkfalls #209238 03/17/13 10:23 PM
Joined: Jun 2004
Posts: 1,273
T
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The nipple 'exception' is there to cover the ubiquitous 'Romex risers' all over America -- coming vertically up out of a panel. Whatever heat buildup induced by such a short run is cancelled by the 'naked' (sheathless) conductors within the panel.

Due to practice, and economics, such long nipples are not seen elsewhere in Romex installations.

========

NEMA standards limit Romex to 3 conductors plus a bare/ papered grounding/bonding conductor.

The NEC is just doing its part to make sure that no-one attempts to bore (hole saw?) oversized penetrations within wall studs. Yes, more, smaller, penetrations result in a stronger stud/ joist.

Anyone stuffing Romex beyond three cables per... is naughty.


Tesla

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