For Aircraft Hangars in NEC 2011, Section 513.8 (A), the code states that All wiring installed in or under the hangar floor shall comply with the requirements for Class I, Division 1 locations.
I have a situation where I'm running 4-inch PVC conduit with 400HZ cables under the slab to a utility pit in the hangar floor. Since I can not use steel conduit for 400HZ system. Is this a code vilation to run PVC under the slab for hangar bay area?
Thanks,
This one has had me buffaloed. I know what
should be OK, but can't quite justify it with the current text. Basically, Section 513.8(A) preempts 513.8(B) since it requires Division 1 wiring in any case no matter what the classification is above the floor. The original purpose for Section 513.8(B) was to eliminate the need for some "boundary seals".
I believe a case of unintended consequences has developed but I'm not sure how or when. Much of Article 513 has been extracted from NFPA 409,
Standard on Aircraft Hangars. I have no trouble finding the basis for Section 513.3 but can't find where Section 513.8 was extracted.
That said, it isn't a violation to run PVC under the slab. Section 513.8(A) essentially defaults to Section 501.10(A)(1)(
a) Exception. You will need to encase the PVC and use RMC for the last 2'. There are a few non-magnetic forms of RMC although not all are suitable for underground. See Section 344.2.
What
should be acceptable but I can't quite justify with the current Section 513.8 text is Section 501.10(B)(1)(6).