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Exception: Steel plates, sleeves, or the equivalent shall not
be required to protect rigid metal conduit, intermediate
metal conduit, rigid nonmetallic conduit, or electrical
metallic tubing.
(F) Insulated Fittings. Where raceways containing
ungrounded conductors 4 AWG or larger enter a cabinet,
box enclosure, or raceway, the conductors shall be
protected by a substantial fitting providing a smoothly
rounded insulating surface, unless the conductors are
separated from the fitting or raceway by substantial
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 provide
a smoothly rounded or flared entry for conductors.
Conduit bushings constructed wholly of insulating
material shall not be used to secure a fitting or raceway.
The insulating fitting or insulating material shall have
a temperature rating not less than the insulation
temperature rating of the installed conductors.
300.5 Underground Installations.
(G) Raceway Seals. Conduits or raceways through
which moisture may contact energized live parts shall
be sealed or plugged at either or both ends.
FPN: Presence of hazardous gasses or vapors may also
necessitate sealing of underground conduits or
raceways entering buildings.
300.7 Raceways Exposed to Different
Temperatures.
(A) Sealing. Where portions of a cable, raceway, or sleeve
are known to be subjected to different temperatures
and where condensation is known to be a problem, as
in cold storage areas of buildings or where passing from
the interior to the exterior of a building, the raceway or
sleeve shall be filled with an approved material to
prevent the circulation of warm air to a colder section
of the raceway or sleeve. An explosionproof seal shall
not be required for this purpose.
300.18 Raceway Installations.
(A) Complete Runs. Raceways, other than busways or
exposed raceways having hinged or removable covers,