NM terminating in exterior box (here we go again)

[ivsenroute]

As an inspector, it is my interpretation that NM cable is not allowed on the exterior of a building, even if it is in conduit. I think that is a given with the industry and am not aware of anyone disputes from all of the posts that I have read here.

I am having an issue because I am running into someone who thinks that you can't even terminate NM in an attached box on the exterior of a structure such as an outlet or disco. This I do not agree with and feel as though this is perfectly acceptable.

Does anyone here terminate NM cable inside then transition to something else for simple items like exterior receptacles or disco's that are directly connected to the structure?

 

[mcclary's electrical]

As an inspector, it is my interpretation that NM cable is not allowed on the exterior of a building, even if it is in conduit. I think that is a given with the industry and am not aware of anyone disputes from all of the posts that I have read here.

I am having an issue because I am running into someone who thinks that you can't even terminate NM in an attached box on the exterior of a structure such as an outlet or disco. This I do not agree with and feel as though this is perfectly acceptable.

Does anyone here terminate NM cable inside then transition to something else for simple items like exterior receptacles or disco's that are directly connected to the structure?

If you bring NM into the back of a weatherproof sealed box, it's not in a location that warrants any transition, however, if it leaves the box ang goes into a conduit, like you said, it at that point needs to be THWN or uf

 

[Dennis Alwon]

It has always been acceptable to run nm to an exterior box as long as the cable is not run past the exterior wall.

If the argument is that nm does not have exterior wiring in the jacket then it makes sense that we should not allow nm to exit a building at all. I think it has more to do with the jacket but I have heard of some inspectors not allowing nm to enter an exterior box.

This definitely needs clarification. Quite frankly I have never seen any issue with NM run to an exterior panel. NM is installed that way all over the country.

 

[Jim W in Tampa]

It's been done for more years than i have wired. The violation for nm is if it is ran in a wet location. Being it is in a weather proof box it is not in a wet location. Is no violation that i see.

 

[iwire]

I am having an issue because I am running into someone who thinks that you can't even terminate NM in an attached box on the exterior of a structure such as an outlet or disco.

Does this person also require 'wet location' fuses and circuit breakers in exterior mounted disconnects and enclosures?

 

[SEO]

Does this person also require 'wet location' fuses and circuit breakers in exterior mounted disconnects and enclosures?

Good analogy.

 

[jwelectric]

312.2 Damp and Wet Locations.
In damp or wet locations, surface-type enclosures within the scope of this article shall be placed or equipped so as to prevent moisture or water from entering and accumulating within the cabinet or cutout box, and shall be mounted so there is at least 6-mm (?-in.) airspace between the enclosure and the wall or other supporting surface. Enclosures installed in wet locations shall be weatherproof. For enclosures in wet locations, raceways or cables entering above the level of uninsulated live parts shall use fittings listed for wet locations.

Does the NM cable pass through this 1/4 inch space? If it does then it is a violation even if it is in a raceway.

300.9 Raceways in Wet Locations Above Grade.
Where raceways are installed in wet locations abovegrade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations abovegrade shall comply with 310.8(C).


334.12Uses Not Permitted.
(B) Types NM and NMS. Types NM and NMS cables shall not be used under the following conditions or in the following locations:
(4) In wet or damp locations

 

[iwire]

Does the NM cable pass through this 1/4 inch space? If it does then it is a violation even if it is in a raceway.

Yeah Mike's right that is what the NEC says.

I say ignore it and move on, I typically seal the top and two sides of outdoor enclosures so the NM would stay dry still a technical foul but oh well.

 

[Dennis Alwon]

If we go by Mike's scenario-- which by the letter of the law is correct, then any outdoor panel would need UF cable run into it.

This whole situation could be alleviated if the NEC would state that NM must have a wet location designated wire installed in it. As I have been told many times by the rep's, nm cable has thhn-2 inside.

I have mentioned it before and I will mention it again that I have seen nm installed underground for over 20 years. Obviously I am not recommending ignoring the code but sometimes good judgement and common sense is all that is needed. :grin:

 

[nakulak]

with all the threads that have been written on this subject, I'm suprised that noone has asked NFPA for an opinion on this (or has someone ?)

 

[maloo]

I'm Iowa the inspectors said that they would allow NM to go from the interior to an exterior outlet or light that is flush to the siding. They did on the other hand say that the soffit of a house is a damp location and an fixtures in the soffit have to be in UF.

 

[480sparky]

I'm Iowa the inspectors said that they would allow NM to go from the interior to an exterior outlet or light that is flush to the siding. They did on the other hand say that the soffit of a house is a damp location and an fixtures in the soffit have to be in UF.

Huh?

So can lights in a soffit must be wired with UF?

 

[raider1]

I'm Iowa the inspectors said that they would allow NM to go from the interior to an exterior outlet or light that is flush to the siding. They did on the other hand say that the soffit of a house is a damp location and an fixtures in the soffit have to be in UF.

So recessed lights in a covered porch would require UF cable run to them?

What is the difference if the cable is over the covered porch or in the attic 2 feet away?

Chris

 

[electricmanscott]

Code issues aside, we have history as proof that a peice of romex terminating in an outdoor box, surface or flush, is not a problem. That's what I, and reasonable people, will continue to do.

 

[peter d]

Does the NM cable pass through this 1/4 inch space? If it does then it is a violation even if it is in a raceway.

That's what caulk is for.

 

[cpal]

it's been recommended and rejected 2008 ROP


(334.12(4) Exception (New) )​

_______________________________________________________________​

Submitter:​

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Dennis A. Portillo, Randolph Community College​

Recommendation:​

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Add new text as follows:
334.12 Uses Not Permitted.
(B) Types NM and NMS. Types NM and NMS cables shall not be used under
the following conditions or in the following locations:
(4) In wet or damp locations
Exception to 4: NM cable shall be permitted to be installed in an approved
enclosure that is installed in a wet location​

Substantiation:​

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This new exception will make it clear that the NM cable used
to supply current to an air conditioner disconnect located on the side of a
dwelling is compliant. This type of installation is done everyday without any
problems as well as for outside panels.​

Panel Meeting Action: Reject
Panel Statement:​

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The existing permitted uses in 334.10 lists uses permitted
unless so restricted by 334.12.​

Number Eligible to Vote: 14
Ballot Results:​

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Affirmative: 14​

__________________________________

 

[rcarroll]

Code issues aside, we have history as proof that a peice of romex terminating in an outdoor box, surface or flush, is not a problem. That's what I, and reasonable people, will continue to do.

And I will continue to pass it.

 

[jwelectric]

That's what caulk is for.

Caulk takes away the requirement for 1/4 inch air space and in itself is a violation.

 

[peter d]

Caulk takes away the requirement for 1/4 inch air space and in itself is a violation.

Oh well.

 

[LarryFine]

Simple suggestion: always bring cable into a flush exterior box from above. That way, water cannot follow or fill the cable.