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How to reconcile multi-rated conductor and NEC 70, Section 338

Question asked by jeffwaa on Mar 11, 2018
Latest reply on Mar 11, 2018 by chiefns830

Section 338 of the 2017 NEC 70 code explicitly forbids the use of USE or USE-2 conductor for above-ground and/or indoor installation. That should be the end of the discussion, but I see conductor that claims to be multi-rated, such as this spec sheet from Southwire:

Southwire Type RHH or RHW-2 or USE-2 conductors are used with conduit as specified in the National Electrical Code. When used as Type USE-2, conductors are suitable for use as underground service entrance conductors for direct burial at conductor temperatures not to exceed 90°C. When used as RHW-2 or USE-2, conductor temperatures shall not exceed 90°C in wet or dry locations. Voltage rating for RHW-2 or RHH or USE-2 conductors is 600 volts.

That statement leads me to believe that the conductors are rated for use as RHW-2 and USE-2 and that it can be used for either application. Can conductor be rated both as RHW-2 and USE-2? If so, how does Section 338 apply?

 

I am fairly new to reading the NEC 70 code book, so I am surprised when it differs from my expectations. I would have expected that Section 338 would identify a property required for indoor use, such as being fire retardant, that USE cable lacks. Perhaps there is an inherent problem, such as temperature differential, with running the same conduit indoors, through a wall to outdoors and underground that I am not familiar with. Please note that those are hypothetical examples that do not need to be explicitly addressed.

 

I would appreciate any information that would clarify my understanding of these issues.

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