Would this be in the gray area of the NEC?

stagger19

Im planning my sub panel install for my garage im bulding. I know I cant run NM-B with Insulation thru conduit. Running conduit all the way from my main breaker box out to the corner where i need to go thru the wall would be tough.

So i was gonna run 6-3 W G NM-B (Romex) out to the corner in the basement and into a juntion box, where the Schd 40 PVC would start, and just strip the insulation of the nm-b and pull the single wires thru the conduit to the sub panel in the garage.

Would this be ok? The single wires within the NM-B cable are THHN, but they dont have the clear plastic covering as well as the outer jacket like true THHN has.

Otherwise, I guess I would have to splice over to single THHN in the junction box, and pull them out to the Sub. I was just trying to make it easier and use the one cable and no splices.

Thanks in advance.....

jwhite

WOW! you sure did hit a grey area, and I have read posts on forums on both sides of the issue about stripping the outer sheath from the nm cable and what the new rating is. IMHO it is not a bad thing to do, but I doubt that the mfg would give your new product any kind of rating. (probably for insurance purposes)

However, in your case it would not be acceptable. You need a THWN rating. Most makers of individual strand wire produce them with a duel rating of THHN/THWN and to be more presise they carry a couple more ratings.

The W in THWN stands for water, and all underground installations in conduit or not, need to have this rating. Electrical conduits will fill with water.

Nice try. I suggest you use the splices at the J box that you mentioned.

stagger19

I didnt know conduit would fill with water. Is that thru the connection leaking or condensation building up in there?




[quote=The W in THWN stands for water, and all underground installations in conduit or not, need to have this rating. Electrical conduits will fill with water.

jwhite

Mostly through condensation as electricians try to do thier best, but the materails are not designed to keep water out. The code requires underground wire be water rated, so the conduit does not need to be designed any other way.

wirenut

Natrulaly you will get water in conduit because of the temperature difference from above ground and below. This causes condensation over and over again thus filling the pipe.