# NM cable-degradation from UV light?



## bach (Apr 11, 2010)

A building inspector in california has cited a property that has NM sheated cable installed in the floor joist area that is above a patio area. It is above 8 feet from grade, has no drywall or any covering. It is not exposed to any direct light, only ambient light, inspector says that the sheathing around the wiring has been damaged from the ambient UV light and has to all be replaced. Does any one have any info about such a thing? Cable is about 16 years old and shows no signs of damage.


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## EES (Jan 4, 2010)

Doesn't matter, either way you need ug wire there anyway.


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## bach (Apr 11, 2010)

The NM cable is an approved conductor for this application if it had been covered with drywall, or something similiar. The question is what if any info is there regarding if any damage can be done from the ambient UV light. I have never heard about this and if there is info out there that would support what I believe, then it should be fine to just cover up the ceiling with drywall.


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## 480sparky (Feb 1, 2009)

334.10 Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following: 
......
(3) Other structures permitted to be of Types III, IV, and V construction except as prohibited in 334.12. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies. 

334.12(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.


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## bach (Apr 11, 2010)

Let me try to be clearer, it is not in a "wet or damp location" had it been covered with drywall. The inspector wants the NM cable replaced with same and covered with drywall. My question is only concerning the UV degradation.


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## AustinDB (Sep 11, 2006)

480sparky, I'm not proficient at understanding the NEC lingo, but would exposed NM in say a garage/workshop (as in stapled to the open rafters/studded walls) be permitted? Just curious...


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## 480sparky (Feb 1, 2009)

72chevy4x4 said:


> 480sparky, I'm not proficient at understanding the NEC lingo, but would exposed NM in say a garage/workshop (as in stapled to the open rafters/studded walls) be permitted? Just curious...



Usually not.

*334.15 Exposed Work.*
In exposed work, except as provided in 300.11(A), cable shall be installed as specified in 334.15(A) through (C).
(A) To Follow Surface. Cable shall closely follow the surface of the building finish or of running boards.
*(B) Protection from Physical Damage.* Cable shall be protected from physical damage where necessary by rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit, or other approved means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit, or other approved means extending at least 150 mm (6 in.) above the floor.


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## 480sparky (Feb 1, 2009)

bach said:


> Let me try to be clearer, it is not in a "wet or damp location" had it been covered with drywall. The inspector wants the NM cable replaced with same and covered with drywall. My question is only concerning the UV degradation.



Normal NM sheathing does not have a sunlight-exposure rating.


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## EES (Jan 4, 2010)

bach said:


> Let me try to be clearer, it is not in a "wet or damp location" had it been covered with drywall. The inspector wants the NM cable replaced with same and covered with drywall. My question is only concerning the UV degradation.


If it's outside and exposed, it's a damp location.


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## Inner10 (Mar 12, 2009)

> 480sparky, I'm not proficient at understanding the NEC lingo, but would exposed NM in say a garage/workshop (as in stapled to the open rafters/studded walls) be permitted? Just curious...


I ran into a situation like this and it ended in a few parts being replaced in MC. The inspector pointed out any spot that the wire could be easily physically damaged. 

Did the jacket of the wire start to go chalky and get brittle? It sounds like the inspcetor is being a little picky, but save yourself some hassle, replace the wire and drywall it over.


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## EES (Jan 4, 2010)

You guys put drywall on the outside of a building up there? The only time I ever see drywall on the outside, is that yellow fiberglass reinforced drywall with plastic tape. And that's only when they are covering it with masonary or stucco. Don't think you are going to get away with putting anything not rated for the location unless you put something on though, like wood or beadboard. Or maybe I am just completely mis-understanding what you are saying.


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## macmikeman (Sep 12, 2005)

480sparky said:


> 334.10 Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following:
> ......
> (3) Other structures permitted to be of Types III, IV, and V construction except as prohibited in 334.12. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.
> 
> ...


If the original poster is referring to a single or two family dwelling (sounds like a probable) than 334.10 (3) is not applicable to that situation, 334.10(1) is which does not require a 15 minute finish. The cable still must be protected from physical damage to what ever degree the local AHJ deems sufficient. As 480 points out , 334.12 (B)(B) applies as well, which would lend some AHJ's to conclude that drywall covering on the underside of the exterior patio is insufficient to provide a dry location. As far as ambient sunlight causing sheath damage,, is a pile of donkey doo. While nm cable does not have a sunlight resistant rating as correctly pointed out by 480, it is my opinion that the particular inspector is taking the fact that 340.12(9) allows uf cable to be exposed to *direct sunlight* if it is listed for it, and confusing it with the poster's situation. Keyword here is *direct* . Neither uf without the sunlight rating or nm cable is allowed to contact "direct" rays of the sun. Nowhere is there a prohibition of "indirect" rays of the sun, meaning ambient conditions found under a roofed structure . So I am going to vote for that inspector to be labeled as full of crap.


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## JumboJack (Aug 14, 2007)

macmikeman said:


> If the original poster is referring to a single or two family dwelling (sounds like a probable) than 334.10 (3) is not applicable to that situation, 334.10(1) is which does not require a 15 minute finish. The cable still must be protected from physical damage to what ever degree the local AHJ deems sufficient. As 480 points out , 334.12 (B)(B) applies as well, which would lend some AHJ's to conclude that drywall covering on the underside of the exterior patio is insufficient to provide a dry location. As far as ambient sunlight causing sheath damage,, is a pile of donkey doo. While nm cable does not have a sunlight resistant rating as correctly pointed out by 480, it is my opinion that the particular inspector is taking the fact that 340.12(9) allows uf cable to be exposed to *direct sunlight* if it is listed for it, and confusing it with the poster's situation. Keyword here is *direct* . Neither uf without the sunlight rating or nm cable is allowed to contact "direct" rays of the sun. Nowhere is there a prohibition of "indirect" rays of the sun, meaning ambient conditions found under a roofed structure . *So I am going to vote for that inspector to be labeled as full of crap*.


I agree to a point.He may be full of it with the UV reason.But NM can't be in a wet or damp location.That would be the reason to site him.


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## macmikeman (Sep 12, 2005)

JumboJack said:


> I agree to a point.He may be full of it with the UV reason.But NM can't be in a wet or damp location.That would be the reason to site him.


Quite right you are about damp just like 480 also posted. I was not disputing the damp part, (well yes, I have heard some squaking lately about how wires inside covered soffits at dwelling exteriors have been getting the "damp" designation from some inspectors, and they are nuts....) the code is quite clear about what constitutes a damp and what constitutes a wet location. That location if no drywall or plywood covering on the underside is damp. And romex is not allowed in damp locations. However the orig poster said he was pinned for "uv light dedigration" to the cable. Since I am not there I have to take his word on the conditions present and the citation wording he received. If it is like he says then they might as well have sited him for having unicorn spit on the cable as well.


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## 480sparky (Feb 1, 2009)

There's always the possibility that there's a local amendment prohibiting anyone from being able to actually lay eyes on NM once a structure is complete. 

There's a few AHJs around me that are like that. If you can see it, it's verboten.


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## AustinDB (Sep 11, 2006)

EES said:


> You guys put drywall on the outside of a building up there? The only time I ever see drywall on the outside, is that yellow fiberglass reinforced drywall with plastic tape. And that's only when they are covering it with masonary or stucco. Don't think you are going to get away with putting anything not rated for the location unless you put something on though, like wood or beadboard. Or maybe I am just completely mis-understanding what you are saying.


 
I've seen drywall on the outside in a few instances, one being a large apartment complex built in the early 70's with brick overtop the drywall. one other instance it had aluminum siding over the sheetrock...


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## aptpupil (Jun 12, 2010)

480sparky said:


> 334.12(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.



licensed electrician did my house and ran NM cable in a crawl space between floor joists. crawl space has exposed dirt, no rat slab or plastic or anything else. are you saying this shouldn't have passed inspection or am i missing something?


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