Opinions sought NM inside conduit outside

[petersonra]

It seems apparent that despite being a perfectly safe and efficient means of wiring in at least some outdoor installations, the code does not allow it.

You can't run NM in damp areas which is an assembly of THWN conductors, but you can run separate THWN conductors. I suppose the argument is the paper inside the NM bundle might get wet, but what harm could that do?

 

[tom baker]

Code is code
We don't like the rules we don't agree with
They are OK for someone else
But not if they cost us time and money.
Mike Holt

 

[JohnJ0906]

You can't run NM in damp areas which is an assembly of THWN conductors, but you can run separate THWN conductors.

Bob, although I have searched for it, I have yet to find any information as to exactly what type conductors are used in the manufacture of NM-B. The only thing I have found is that they are 90 deg.
I certainly have found nothing to suggest that the conductors have a "W" rating.

 

[markstg]

Bob, although I have searched for it, I have yet to find any information as to exactly what type conductors are used in the manufacture of NM-B. The only thing I have found is that they are 90 deg.
I certainly have found nothing to suggest that the conductors have a "W" rating.

From Southwire:

Southwire's Romex SIMpull? Type NM-B cable is manufactured as 2, 3, or 4 conductor cable, with a ground wire. Copper conductors are annealed (soft) copper. Conductor insulation is 90?C-rated polyvinyl chloride (PVC), nylon jacketed.

THWN is Thermoplastic Insulation with a Naylon Jacket.


Southwires definitions:

Technical Information & Technical Bulletins



THW-2: Thermoplastic Insulation (usually PVC), Heat Resistant (90?C rating), suitable for Wet locations.



THWN-2: Same as THW except Nylon jacket over reduced insulation thickness. Also rated THHN.



THHN: Thermoplastic Insulation (usually PVC), High Heat Resistant (90?C rating), dry locations only, Nylon jacket. Also rated THWN


Hmmmm.... Seems Thermoplastic is PVC to Southwire.

 

[JohnJ0906]

From Southwire:

Southwire's Romex SIMpull? Type NM-B cable is manufactured as 2, 3, or 4 conductor cable, with a ground wire. Copper conductors are annealed (soft) copper. Conductor insulation is 90?C-rated polyvinyl chloride (PVC), nylon jacketed.

THWN is Thermoplastic Insulation with a Naylon Jacket.


Southwires definitions:

Technical Information & Technical Bulletins



THW-2: Thermoplastic Insulation (usually PVC), Heat Resistant (90?C rating), suitable for Wet locations.



THWN-2: Same as THW except Nylon jacket over reduced insulation thickness. Also rated THHN.



THHN: Thermoplastic Insulation (usually PVC), High Heat Resistant (90?C rating), dry locations only, Nylon jacket. Also rated THWN


Hmmmm.... Seems Thermoplastic is PVC to Southwire.

NM-B

Building wire and cable specs

It does seem to be the same stuff - and UF conductors are defined the same way. But, SE cable has the type of conductor expressly stated - XHHW. MN-B does not.
Until I see where a manufacterer specifically states the type of conductor used in romex, I will keep my opinion that we do not actually know what conductor is actually used. And I certainly will not assume that the conductor has a "W" rating, until I see that fact directly stated.


BTW, the UL White book is silent on this issue.

 

[JohnJ0906]

One thing that slides by here all the time is rooftop AC circuits.

Up until the late 80's early 90's, everyone here used SE cable for the AC circuits. When #8 and #6 NM came onto the market, everyone started using it instad of SE.

Typically, about 2' of cable stubs up thru the roof and hits the AC disconnect but no one really cared about it. There MAY be a specific local variance but I think it was basically a non issue and no one thought twice about it.

Is this 2' exposed, or in conduit?
If exposed, I would be more concerned about UV damage than moisture - especially in your neck of the woods.

 

[LarryFine]

You can't run NM in damp areas which is an assembly of THWN conductors, but you can run separate THWN conductors. I suppose the argument is the paper inside the NM bundle might get wet, but what harm could that do?

No, the argument is that NM conductors are not marked or labeled.

Your local AHJ might accept the manufacturer's specifications.

 

[petersonra]

No, the argument is that NM conductors are not marked or labeled.

Your local AHJ might accept the manufacturer's specifications.

I am not suggesting code permits it, or that it is OK to violate the code when it is convenient.

Only that it is odd that the exact same conductors (given proper marking, etc.) could well be run in an exterior conduit by themselves, but not as part of an NM assembly.

 

[weressl]

Inside a conduit is not a location. If the conduit is outdoors, so are the conductors within.

Not really.

The outer enclosure rating overrides the installation provision, unless it is specifically prohibited.

 

[LarryFine]

The outer enclosure rating overrides the installation provision, unless it is specifically prohibited.

English, please. :-?

 

[radiopet]

Isn't UF a non-metallic sheath cable?

But it ain't an NM-B Cable.

 

[220/221]

Is this 2' exposed, or in conduit?
If exposed, I would be more concerned about UV damage than moisture - especially in your neck of the woods.

It is not exposed.

We don't expose cables here.

We do still sleeve it in conduit though :roll:

I think it's funny that an outdoor panel is not considered a wet locaion because the NM is allowed inside it.

I feel that the code makers didn't think this one through all the way.

You can of course install JB's and change to THWN but it just adds more splices to the circuit and more bulk to the installation. The installation of sleeved NM is just as safe and durable as THWN, it's just not legal since 08.

I have reworked a lot of cabling over the years and have never seen any damage due to sleeved NM outdoors above grade. I have however seen a lot of damage at connectors and staples

 

[peter d]

We don't expose cables here.

We expose lots of cables here. All the time. Try it sometime. It's kind of liberating.

 

[Twoskinsoneman]

Those six people are wrong. A conduit's interior is not a location.

The conductors inside a conduit that is outdoors are also outdoors.

I would like to say I disagree with this completely. The conductors are not outdoors because they are in conduit that is outdoors. They are in a wet location because the NEC specifically says that the interior of a raceway in a wet location shall be considered a wet location.
IMO conductors inside enclosures that are in wet locations are not in wet locations.
And the reasoning is simple. The code does not say that the interior of enclosures are wet locations unless they are underground.

So cables/conductors also devices (like circuit breakers and terminal buses) in enclosures in a wet location do not have to be listed for wet locations.

 

[Dennis Alwon]

And the reasoning is simple. The code does not say that the interior of enclosures are wet locations unless they are underground.

So cables/conductors also devices (like circuit breakers and terminal buses) in enclosures in a wet location do not have to be listed for wet locations.

Check this out

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).

 

[Twoskinsoneman]

The code does not say that the interior of enclosures are wet locations unless they are underground.

So cables/conductors also devices (like circuit breakers and terminal buses) in enclosures in a wet location do not have to be listed for wet locations.

Check this out

Check this out

Enclosure. The case or housing of apparatus, or the fence
or walls surrounding an installation to prevent personnel
from accidentally contacting energized parts or to protect
the equipment from physical damage.

 

[Dennis Alwon]

Check this out

Enclosure. The case or housing of apparatus, or the fence
or walls surrounding an installation to prevent personnel
from accidentally contacting energized parts or to protect
the equipment from physical damage.

Perhaps a raceway is a type of enclosure but that does not negate 300.9. I just can't agree with you here. Not all enclosures are raceways and 300.9 is specific to raceways.

 

[Twoskinsoneman]

Perhaps a raceway is a type of enclosure but that does not negate 300.9. I just can't agree with you here. Not all enclosures are raceways and 300.9 is specific to raceways.

Wow I just have no clue what you are talking about.

I didn't say anything about negating 300.9.... It just doesn't pertain to enclosures.

And I'm not following the statements "Perhaps a raceway is a type of enclosure" and then " Not all enclosures are raceways"

Just to be clear...my points of interest were:

1. the interior of raceways in wet locations are considered wet locations (arguing Larry's: interior of raceway is not a location)

2. the interior of enclosures in wet locations are not considered wet locations.

Raceways and enclosure are not the same nor does either one include the other.

 

[Dennis Alwon]

Well, I guess we are somewhat on the same page. I thought you were arguing that the inside of a raceway was not a wet location by using the enclosure statement as proof. Guess I misunderstood what was going on-- that's nothing new.... oh well.

 

[Twoskinsoneman]

No, we agree...This is from my earlier post...

the NEC specifically says that the interior of a raceway in a wet location shall be considered a wet location.

Looking back I should have better divided that post up to make my two separate points more clear.