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...
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.
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.
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 !