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Nm-B in outdoor panels?

PCustoms

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Jul 23, 2011
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Location
VT
NM-B isnt allowed in wet locations, is it allowed to pass through a wall into a 3R exterior panel?

If so, why?
 
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billconner

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Jul 20, 2021
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Thousand Islands NYS
Love your questions. You should apply to be on a code committee. I asked questions about fire codes on 1987, been on the NFPA assembly committee ever since.

If the Romex is in the wall and then into a surface mounted box, is it really exposed? Certainly seems regularity allowed on recessed boxes opening to wet locations.
 
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PCustoms

Well-known member
Joined
Jul 23, 2011
Messages
23,684
Location
VT
If the Romex is in the wall and then into a surface mounted box, is it really exposed? Certainly seems regularity allowed on recessed boxes opening to wet locations.
I think there was a discussion on this recently, and the consensus was technically not OK but done often.

For the record I'm not an electrician, just have played one for a while and had 2 masters and several apprentices that I supervised in an industrial setting. I'm just an inquisitive person and can see where some code is life safety and others appears to be $$ safety for the mfg.

Also for the record my outdoor outlets and lights are wired with Romex through the wall into the boxes and I'm pretty sure my security light is Romex into sealtite in an exposed location. That was fixing a real **** install in a half-*** way. Previous owner (supposedly an actual electrician) ran Romex inside the vinyl siding trim up to each corner of the house to lights....
 

mm08822

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Jan 13, 2012
Messages
6,230
Location
NJ
NM-B and UF-B both have conductor insulation that complies with UL 83 which is THHN/THHW. NM-B has the kraft paper filler that is is a moisture wick for sure. Since the PVC jacket and kraft paper is generally removed upon entry into the box or enclosure I don't see it as any different than UF or THHW emerging out of conduit into the same space.

Many WP boxes and panel enclosures are recessed into the wall so the PVC jacket isn't exposed to the wet/damp environment, it is still interior space. For those surface mounted, many are protected from water with a ****** or some type of caulk/duct seal to close up the hole in the siding/sheathing to prevent water/air infiltration into the wall.

I don't see anyone running UF to any box or panel for this limited exposure. Should we run UF in kitchens, bathrooms, wet bars, etc?
 
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