NM in PVC Conduit, on Roof

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Bill Annett

Bill Annett

Senior Member
Location
Wheeling, WV
Occupation
Retired ( 2020 ) City Electrical inspector
Did an inspection today where the contractor ran NM cable from a panel on the first floor thru the second and third floor and then penetrated the roof with a short piece of PVC conduit ,then to carflex, to a disconnect for an AC unit. I told the contractor that NM could not be in a conduit outside because it is considered to be a wet location. I am home and left my code book in the office but I think that I cited code section 300.9. He said that if he strips off the jacket of the NM that he would be ok. I do not agree with that. His wiring method is NM. It started out as NM and has no splices so I can not see how it now could not be NM. AM I missing something? Any input will be appreciated. Code references will even be better.

I did not have a good day at work. On the way home I stopped and bought some Chinese food. The fortune cookie said ? If you have a job without aggravations, you don?t have a job? The next time That I do not have a good day at work, I think that I will just get a Big Mac.

Thanks, I will check back to see your opinions. If I am wrong please let me know.
 
Jumper and North Star.

No they did not. They fire caulked all holes and used a boot on the roof for the PVC. This is a 6 unit apartment building, it is all roughed in and this was the only problem. In Wheeling apartment buildings with 3 or more units, the fire Department also inspects the fire caulking and life safety issues.

Bill
 
Bill Annett said:
Jumper and North Star.

No they did not. They fire caulked all holes and used a boot on the roof for the PVC. This is a 6 unit apartment building, it is all roughed in and this was the only problem. In Wheeling apartment buildings with 3 or more units, the fire Department also inspects the fire caulking and life safety issues.

Bill
Click to expand...

Still, it it is red tag/fail. Not legal. Common violation.
 
jumper said:
310.8 and 310.11. Installer is wrong.

I only know that NM-B has 90C conductors, nothing else.
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300.9 does apply, 310.8 and 310.11 from 2008 NEC apply but are gone in 2011.

310.120 appears to be same thing as former 310.11, can't seem to find anything that resembles 310.8, but imagine there is something somewhere that is almost word for word the same thing.
 
Bill Annett said:
Did an inspection today where the contractor ran NM cable from a panel on the first floor thru the second and third floor and then penetrated the roof with a short piece of PVC conduit ,then to carflex, to a disconnect for an AC unit. I told the contractor that NM could not be in a conduit outside because it is considered to be a wet location. I am home and left my code book in the office but I think that I cited code section 300.9. He said that if he strips off the jacket of the NM that he would be ok. I do not agree with that. His wiring method is NM. It started out as NM and has no splices so I can not see how it now could not be NM. AM I missing something? Any input will be appreciated. Code references will even be better.

I did not have a good day at work. On the way home I stopped and bought some Chinese food. The fortune cookie said ? If you have a job without aggravations, you don?t have a job? The next time That I do not have a good day at work, I think that I will just get a Big Mac.

Thanks, I will check back to see your opinions. If I am wrong please let me know.
Click to expand...

Inspector without a code book??:(

That is most important tool you have. If you did that to me, even if I knew you were probably right, I would want you to be able to give (and show) me what I have violated. If you were AHJ here you have to give applicable code section with correction notices. (Your 300.9 BTW is not wrong but only confirms that inside raceway is a wet location, you still need a code section that says NM cable can not be used in wet location to go along with it) Jumper's sections apply to the other part about stripped NM cable for 2008 and then what I said for 2011.
 
NM, rooftops, and PVC

NM, rooftops, and PVC

NM conductors are rated 90 degrees C. They are somewhat like THHN without the nylon jacket. Unless they are marked (THHN ...) you can't strip them out of the jacket and use them as individual conductors. I've seen some NM with marked conductors in it. NM and hence the conductors are not rated for wet locations. As far as I know, outdoor conduits are wet locations.

2008 NEC:

100 Equipment. A general term including material, fittings, ....

110.3(B) Installation and use. Listed or labelled equipment shall be
installed and used in accordance with any instructions included in the
listed or labeling.

2012 UL White Book:

NONMETALLIC-SHEATHED CABLE
(PWVX)
USE
This category covers Types NM-B and NMC-B nonmetallic-sheathed
cable, rated 600 V, intended for use in accordance with Article 334 of
ANSI/NFPA 70, ??National Electrical Code?? (NEC), and Listed in copper
sizes 14 to 2 AWG inclusive and aluminum or copper-clad aluminum sizes
12 to 2 AWG inclusive.
This cable contains conductors rated 90?C; however, the ampacities of
the cable are those of 60?C conductors as specified in Article 334 and Table
310.16 of the NEC.

No mention of individual conductors being listed. No mention of wet locations

2008 NEC:

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).

310.8(C) Wet Locations. Insulated conductors and cables in wet locations shall
comply with one of the follow:
....
(2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN-2,
XHHW, XHHW-2, ZW
(3) Be of a type listed for use in wet locations

334.112 FPN:
NM-B cable is NM cable with 90 degree conductors.


2008 NEC 334.12(B) ...shall not be used in the following conditions or locations:
....
(4) In wet or damp locations.


I'd be willing to bet that the installation also violates 310.15(B)(2)(c) rooftop ambient temperature,
353.30 supports, and 352.44 expansion.

I'm getting ready for the master's test and so am practicing chasing through the NEC.:D
 
310.120
All conductor and cables shall be marked...

You can't strip the sheath off of NM cable because the conductors are not marked. It is listed for use as a cable and ONLY a cable.
 
Good Morning.

I would like to thank everyone for the information. The code references were great. I posted this question because I wanted to know if I was interpreting the code sections correctly. You are correct, I do have to give the section of the code when I believe something does not meet code. I have a code book at the office which the city bought. I have one in the car, which I paid for. I could not afford to pay for another one for the house. This is a great site and I would like to again, thank every one for their input.

Bill
 
roger said:
I've heard other people say that too but they have never been able to prove it.

Roger
Click to expand...

Yep. Unlike MC, which Southwire tells me has THHN/THWN, For NM, Southwire just says "Conductor insulation is
90?C-rated polyvinyl chloride (PVC), nylon jacketed."

So even if it was marked, that really would not help because there is no marking that the NEC recognizes.

It very well could be THHN, but they ain't saying.
 
jumper said:
Dude said he was at home.
Click to expand...

Bill Annett said:
Good Morning.

I would like to thank everyone for the information. The code references were great. I posted this question because I wanted to know if I was interpreting the code sections correctly. You are correct, I do have to give the section of the code when I believe something does not meet code. I have a code book at the office which the city bought. I have one in the car, which I paid for. I could not afford to pay for another one for the house. This is a great site and I would like to again, thank every one for their input.

Bill
Click to expand...

I misunderstood, somehow interpreted as he was inspecting and code was at home, sorry.

jumper said:
Yep. Unlike MC, which Southwire tells me has THHN/THWN, For NM, Southwire just says "Conductor insulation is
90?C-rated polyvinyl chloride (PVC), nylon jacketed."

So even if it was marked, that really would not help because there is no marking that the NEC recognizes.

It very well could be THHN, but they ain't saying.
Click to expand...

Not trying to nit pick but I will anyway to clarify something. THHN is not for wet locations, THWN is. Most of what we buy has both ratings on it. If NM conductors were marked and they said THHN only they would still be dry location conductors.
 
mjf said:
In the past I have occasionally stripped back NM and sleeved it in 1/2" EMT. This was in a dry location. Was this was code compliant. If not, I wonder why they manufacture what I call a "from-to".
Click to expand...

Technically probably not but I would not loose sleep over it.
 
kwired said:
Not trying to nit pick but I will anyway to clarify something. THHN is not for wet locations, THWN is. Most of what we buy has both ratings on it. If NM conductors were marked and they said THHN only they would still be dry location conductors.
Click to expand...

I know this, it was kinda my point. We really only know that it is a "90?C-rated polyvinyl chloride (PVC), nylon jacketed" conductor.

That is not THHN or anything else listed in 310.13, and so as such you could not strip it and use it in conduit legally even in a dry location.

NM cable is recognized and therefore, as an assembly you can use it.

I know you know all this, I am just clarifying my position.
 
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