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Tuesday, July 15, 2003
Question:
I've been reading and learning from the daily code question for almost 2-years now and couldn't get by without it and a cup of coffee in the
morning. I work for an electrical wire and cable manufacturer and we frequently get application questions. Our typical response is to try to
help point to the relevant section of the code and always recommend that they consult with a qualified electrical system designer and their local jurisdiction having authority.
One common question has to do with wet locations for 600V building wires like RHW, XHHW, THWN --- are they suitable to be installed underground (typically in conduit) where the system is always underwater? The Code defines dry, damp, and wet, but wet location doesn't seem to extend to "submersed."
We received this question yesterday from an amusement park: "the standard listing for type RHW conductor is suitable for wet location but can
it be installed in conduit that could be filled with water and/or chlorinated water all the time?"
Can "Code Question of the Day" take a stab at answering?
Regards,
Tom Lewnard
Product Manager
A
Answer:
Hey Tom, thanks for your nice comment. A cable that has a “Type W” designation cannot be used in a system where the design intends that the conduit be filled with water. The NEC definition of a “wet location” does not include being submerged in water. A cable designed for use submerged in water requires, I believe, an outer covering such as PVC.
There is a cable listed for use with submersible pumps and marked “submersible pump cable” which is part of an assembly used for well pumps. There is also a new requirement in 680.56(B) that requires that “flexible cord immersed in or exposed to water shall be of a type for extra-hard usage, as designated in Table 400.4 and shall be a listed type with a “W” suffix
The NEC covers the situation with requirements that say “310.8(C)(3) “Of a type listed for use in wet locations” or 310.9 “of a type suitable for the application.” “Listed” and “Labeled” are defined in Article 100.,