Have any of you seen or intalled nm cables into the top of a panel via a 2" or 3" pvc nipple instead of thru separate nm connectors? I've seen this at a couple locations, never did it myself, but I thought I saw something in the NEC addressing this by way of an exception. Either that or I saw it in a book or magazine article. I'm just trying to find out about this for a friend, he said his son's house was wired that way. I'd think there would be issues about securing the cables at least. I figured someone here may know something about this. thanx...

As I understand it in some areas of the country this is the normal practice regardless of the NEC restrictions on it.

The NEC does allow NMs to be brought in to a panel through just a pipe sleeve....under very restricted conditions.

I don't have my code book handy, I will try to post the section number soon.

From memory.

The panel and the pipe(s) must be surface mounted.

The pipe must go up from the panel, not down.

There is both a minimum and maximum length of the pipe.

It the pipe can not enter into the structural ceiling.

I think this is an area where the code does not specifically say something .... kind of gets back to the "this is not an instruction manual, and assumes you already know what you're doing" part of the introduction.

I believe that the NEC allows NM to be run in pipe for protection against physical damage. I believe that the NEC further requires that NM run exposed below a certain height (7 ft?) be protected.
Combine the two, and you wind up with plenty of panels and furnace disconnects having stubs of pipe coming out the top.

If I remember correctly, I don't think the NEC requires any fitting to soften the edge of the pipe ... though that would clearly be a good idea.

This may be a carry-over from K&T days:

312.5(C) ex
Exception: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 450 mm (18 in.) or more than 3.0 m (10 ft) in length, provided all the following conditions are met:
(a) Each cable is fastened within 300 mm (12 in.), measured along the sheath, of the outer end of the raceway.
(b) The raceway extends directly above the enclosure and does not penetrate a structural ceiling.
(c) A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.
(d) The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.
(e) The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm (1/4 in.).
(f) The raceway is fastened at its outer end and at other points in accordance with the applicable article.
(g) Where installed as conduit or tubing, the allowable cable fill does not exceed that permitted for complete conduit or tubing systems by Table 1 of Chapter 9 of this Code and all applicable notes thereto.

Thank you, Greg.

I imagine a search would bring back the conversation we had 5 years ago when this showed up in the 2002

thank you, that was what I was looking for.

One gross violation of 312.5 (C) that is shown in electrical publications, as if it is not a violation, involves the advetising by a cable company that introduced NM in different colors.
They show a panel with a all the NMs entering through a single 2 inch knock out.
Even the IAEI in their advertising show a white wiskered old man with his white hard hat looking at a panel with all the NMs entering a single knock out.
I have had contractors try to get by with six inch stubs and inside walls thinking this complied with the Code.
It does not !

(d) The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.

What are approved means for sealing/plugging the end of a pipe with multiple cables entering it?

steve

Check out 'Approved in Article 100.

Approved is not the same as listed, approved only means its OK with the AHJ.

I would bet duct seal would be acceptable to most.

What about derating???

Dave

If the conduit is under 24", it doesn't need to be derated, right?

If the section of pipe is less than 24" no derating needed.

If the pipe is longer then 24" the derating must be done but will not change anything until you get past 9 current carrying conductors with 15, 20 and 30 amp circuits.

I do find it interesting that if you stuff some insulation in the hole in a top plate you need to derate RX but you can stuff a stack like this with duct seal or some other inspecified material without derating.
Things that make you go "huh?".