ECN Forum Forums Code Related Discussion NEC & other Code issues Romex in pipe

Some very good points on why not to use NM wire in EMT, they do make sense.
Of course, here in Arizona we don't have to worry much about moisture.
(Also just wanted to point out, you can use NM in EMT for mechanical protection in a dry invironment).

hi,
ok how about this...an fs box is mounted on an exterior wall of a single family dwelling...once the cable enters the fs box it is stripped and then the conductors are run in a pvc conduit to a shed...120VAC...

where is the problem?

how about a sub panel in a attached garage with a 2" piece of pvc sch 40 extended into the cieling, filled with several 12/2, 12/3, 3C/6?

is this legal?

-regards

frodo

Frodo,

If that PVC conduit runs underground, then there's a problem if the conductors are not THWN. I dunno if NM-B conductors are dual THHN/THWN, and I'm too comfortable to get up, go to the garage, and look.

On the 2" PVC running from a surface mount panel to the attic space--look at table 310.15(B)(2)(a) "Adjustment Factors for More Than Three Current-Carrying Conductors in a Raceway or Cable". If the length of the pipe is more than 24", these factors must be applied (310.15(B)(2)(a).

Also, in Annex B, Table B.310.11 gives adjustment factors for more than 3 current-carrying conductors in raceway or cable with load diversity. Because of the load diversity, you don't have to give up as much ampacity. I think you'd have a tough time getting an AHJ to agree to this approach (load diversity) in a dwelling occupancy.

Cliff

Cliff,
Have you read the italics, the second line, under ' Annex B - - - - '?

I believe the basic answer is:

1)NM cable is not approved for wet locations, regardless of the conductors on the inside. The covering will absorb moisture and due to the wicking phenomena, the paper filler will draw moisture into whatever enclosure the NM terminates in.
2)If any conduit is installed in a wet location,(outdoors or underground) the interior of that conduit is also a wet location. Therefore no NM.

Most all the breaker panels on homes here in Arizona are mounted on the outside of the house in a weatherproof panel, (a wet location during the short monsoon season) which means all romex terminations are in a wet location. umm..

Any comments about the outdoor breakers panels?

I'll give it a try-

Conduits in wet locations may fill with water and if underground, will probably never dry out. If NM cable is inside, the jacket will become saturated and the paper filler will transmit moisture to the termination points. An outdoor breaker panel will probably never fill with water and has 90% of the jacket & paper removed anyway. It seems unlikely that enough moisture will be present to cause any problems.
But that's just my opinion.
BTW,
I don't like the idea of outdoor residential panels anyway. Are they that common, guys?

I never really thought outdoor breaker panels outside were a great idea either, but never-the-less probably 99% here in AZ are outdoor. They are "all in one" type - meter and breakers combined in one panel.

If they are in a 3R type enclosure, the wiring and terminations are not supposed to be getting wet. The NEMA test requirement for 3R panel is the entire top, and all exposed sides are sprayed with water at 5 psi for one hour at a rate to cause water to rise 18" in a straight sided pan placed beneath the enclosure. The evaluation is: no water shall have reached live parts, insulation or mechansims. If the panel is a NEMA 4 or 4X then the same test is used but the evaluation is: no water shall have entered the enclosure.
Don(resqcapt19)