NM in conduit

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torcho

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Okay, I know this subject has been covered a thousand times (I don't feel like searching the forums) so here I go. Therotically speaking, let's say I need to provide provisions for an air conditining condensing unit in a residental home. I will be running 10-2nm cable from my indoor panel to an outside disconnect (yes, I always re-identify the current carrying conductors with a red paint pen) In this situation, I cannot stub the wire out directly behind the disconnect, so I will have to stub it out below the disconnect. Here is the question...I want to use an EMT LB or service entrance elbow and a short piece of 3/4 emt to feed in to the bottom of the disconnect, we are talking about three feet of exposed conduit; so...is this okay using standard NM-B, or should I supply a j-box inside the house, then pipe to the disconnect using THWN? I hope I don't get a rash of gunfire on this question, but hey, I didn't ask ground up or down on receptacles....I look forward to your replies.
 
torcho said:
I want to use an EMT LB or service entrance elbow and a short piece of 3/4 emt to feed in to the bottom of the disconnect, we are talking about three feet of exposed conduit; so...is this okay using standard NM-B . . . ?
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Technically, it's non-compliant, just as is doing the same thing for branch circuits with exterior panels. In practice, it's probably the most-permitted violation around. If you want to be sure, ask the inspector.


I once ran NM through Carflex through a pitch-pocket for a roof-top receptacle to service HVAC equipment. The inspector said "You can't run NM outside the building! Strip the sheath off where it goes throuh the roof."

I glued a female terminal on the inside end of the Carflex, screwed in a 2-screw cable clamp, stripped the rest of the NM, and fed it through to the FS box. He liked it, I liked it, it was cheap and tidy, and I would do the same again.
 
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I'm confused

I'm confused

LarryFine said:
Technically, it's non-compliant, just as is doing the same thing for branch circuits with exterior panels. In practice, it's probably the most-permitted violation around. If you want to be sure, ask the inspector.


I once ran NM through Carflex through a pitch-pocket for a roof-top receptacle to service HVAC equipment. The inspector said "You can't run NM outside the building! Strip the sheath off where it goes throuh the roof."

I glued a female terminal on the inside end of the Carflex, screwed in a 2-screw cable clamp, stripped the rest of the NM, and fed it through to the FS box. He liked it, I liked it, it was cheap and tidy, and I would do the same again.
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So you are saying if I were to punch my 10-2 NM into a j-box RIGHT before I go "outside" with it and run THWN to the disconnect, it would be compliant? That is how I see the NEC needs it to be done. But I just don't understand, you said the thing about the home runs to outdoor panels, so that means that my outside outlets, light fixtures, etc. are not code compliant using NM? I am NOT arguing with you, I respect your answer, I just am trying to find that "fine line" ....should I throw away all my NM and buy UF instead? I am assuming UF would not incur any NEC violations? What do you think? Thanks...

Edited to add: You know, I wouldn't mind doing everything with EMT (I like the stuff) using dual listed THHN/THWN and avoid all these problems.
 
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You could always use UF for the entire run; for interior wiring it can be used anywhere you can use NM, and it is also rated for wet locations or underground.

-Jon
 
I had a similar situation recently. I run nmb to a j-box and converted to pvc and thwn to go outside.

The inspectors in my area will not allow nm to be stripped because the individual wires are not labeled. Ridiculous in my opinion, a simple label would make it legal. But it's code and I don't argue.
 
Jomaul said:
What code article are you refering to that prohibits NM cable from being used in such a manner?
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Jomaul, NM is not listed for wet location. Althought the wire in the cable is 90C it isn't marked so we don't know if it is Thhn or Thwn or a combo of the two. Art. 334.12(B)(4).

Even though the cable is in a conduit outdoors it would be still be considered wet location.
 
My inspector also sites 310.11 Marking. Although the cable is marked if it is stripped back he cannot see the nm sheath. Therefore to his thinking it cannot be stripped for indoor use either.
 
The problem with using NM in a wet location (other than it's listing) is with the paper filler that's used in the manufacturing process.

It wicks water.

I don't know how far the water will travel, but I've seen some NM cable where the paper was wet at least 10 feet into the cable.

Since there's no way to tell exactly what type insulation is on the conductors, it's not listed for use in wet locations.

I agree that a simple solution would be for the wire manufacturers to mark the conductors with the insulation type.
That way, the outer covering could be stripped and eliminate this "wicking" where the cable is run outside for short distances, such as at outside disconnects located on the side of the residence.

Just a opinion
steve
 
Dennis Alwon said:
Jomaul, NM is not listed for wet location. Althought the wire in the cable is 90C it isn't marked so we don't know if it is Thhn or Thwn or a combo of the two. Art. 334.12(B)(4).

Even though the cable is in a conduit outdoors it would be still be considered wet location.
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dennis read the def of dry location
 
I've never had a problem with bringing NM to a j-box and then running conduit to discos or what have you. I think the problem stems from the possibility of condensation inside the pipe and with the dry locations only rating on NM is where AHJ's red tag such an installation.
 
porch light okay ?

porch light okay ?

does it not pass code to use nm for a porch light feed directly into back of a surface mount fixture box ? Does a flush mounted box pass since the wires dont leave face of building.
 
Jomaul said:
dennis read the def of dry location
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Location, Dry. A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a building under construction.
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And? :confused:

Inside a conduit, a raceway, or enclosure is not a location. A conductor or cable inside a conduit that is outdoors is still outdoors.
 
Come on guys this smells to me to be up for review. Maybe the powers that may be could impose a limit to the length of sheathing in the conduit. I mean how inconvenient to change over in a box. I'm sure that 5 feet or so would i all realistic situations not make the slightest bit of difference in the ampacity of the wire. Sometimes they really make it inconvenient to make a buck dont they?
 
Jomaul said:
dennis read the def of dry location
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A conductor or cable in a conduit exposed to the weather must be listed for wet locations. Read the definition of Location, Wet. The Handbook (Though only opinion) elaborates to say that "the inside of a raceway in a wet location is considered a wet location".
 
I don?t know guys I see it as okay in light of 334.15(B). You do have a different formula regarding conduit fill.

Chapter 9 Table 1, Note (5): "For conductors not included in Chapter 9, such as multiconductor cables, the actual dimensions shall be used."
This formula is: Square Inches = cable outside diameter squared x (3.1416/4) x Qty of cables
 
Chapter 9 Table 1, Note (5): "For conductors not included in Chapter 9, such as multiconductor cables, the actual dimensions shall be used."
This formula is: Square Inches = cable outside diameter squared x (3.1416/4) x Qty of cables
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But don't forget that you also have to apply note 9 for NM or UF type cables.
(9) A multiconductor cable of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter.
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Don
 
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