Under Ground Conduit Below Hangar Floor

[faresos]

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,

 

[rbalex]

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).

 

[faresos]

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).

Thank you Bob for your response. Digging more into it, I found out the NEC allows the use of rigid aluminum conduit in concrete or directburied ?where provided with approved supplementary corrosion protection.?
That means that additional corrosion protection must be applied and it must meet the approval of the AHJ.

Uses Permitted
344.10 (A)(3)
Aluminum RMC. Aluminum RMC shall be permitted
to be installed where judged suitable for the environment.
Rigid aluminum conduit encased in concrete or in direct
contact with the earth shall be provided with approved supplementary
corrosion protection.