NEC requirements for underground wiring in Class I, Division 1 locations
When installing polyvinyl chloride conduit (PVC) or reinforced thermosetting resin conduit (RTRC) as a Class I, Division 1 wiring method for an underground installation in a tank farm area, which statement is not true?
A. The conduit(s) must be installed with 24 in. of cover over the top of the concrete, which encases the conduit.
B. The conduit(s) must be covered by at least 2 in. of concrete.
C. The conduit(s) must be encased in a concrete envelope by at least 2 in. of concrete.
D. Where entering or emerging from the ground, the wiring method must change to another type, such as rigid metal conduit (RMC) or intermediate metal conduit (IMC).
A concrete cover of at least 2 in. is not sufficient in this particular situation. The 2011 NEC requirement is to encase the conduit(s) in a concrete envelope at least 2 in. thick, as well as providing 24 in. of cover, and where entering or emerging from the ground, the wiring method must change to another type, such as RMC or IMC. See the Exception in 501.10(A)(1)(a).
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