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.
(B) Expansion Fittings. Raceways shall be provided with
expansion fittings where necessary to compensate for thermal
expansion and contraction.