300.4(G) Insulated Fittings. Where raceways contain 4 AWG
or larger insulated circuit conductors, and these conductors
enter a cabinet, a box, an enclosure, or a raceway, the con-
ductors shall be protected by an identified fitting providing
a smoothly rounded insulating surface, unless the conduc-
tors are separated from the fitting or raceway by identified
insulating material that is securely fastened in place.
Exception: Where threaded hubs or bosses that are an
integral part of a cabinet, box, enclosure, or raceway pro-
vide a smoothly rounded or flared entry for conductors.
Conduit bushings constructed wholly of insulating ma-
terial shall not be used to secure a fitting or raceway. The
insulating fitting or insulating material shall have a tem-
perature rating not less than the insulation temperature rat-
ing of the installed conductors.