Air Craft Hangar Underground

[manush 562]

We are installing six sub panels in seperate hangers (200 amps each) we installed the underground 24" below finished floor with PVC, we finished the run with gal conduit into the sub panel, the gal conduit is min. 24" deep under the slab. As I interpet the code we need no seal offs as we enter the sub panel, because we have no couplings, connectors as we pass thru the 18" on floor level are we correct?

 

[rbalex]

You need to review Section 513.8.

 

[dennis schaffert]

aircraft hanger

aircraft hanger

I believe you should review article 501 specifically areas concerning boundaries
considering that you have no fittings before your panel does not eliminate the need to seal of as a boundary I personally would rather feel safe than sorry for the cost of a 2" seal off

 

[dennis schaffert]

aircraft hanger

aircraft hanger

I thought maybe I should expand on this, as I interpet it ,your conduit is entering a classified area, thus requiring a seal off , as I see it you saved a bundle with the PVC under ground rather than over head just remember that the percentage of fill for a seal of is 25 % if you have limited the size of your conduit and up sized your feeder for voltage drop you may have to increase the size of your seal off to the next trade size of conduit and connect with reducer bushings

 

[rbalex]

This is a PM I received from manush52 and my response

.

Originally Posted by manush 562
yes 513.8 will refer you to class 1 division 1 Boundary 501.15 which states in exception no.1 you may pass thru the class 1 division 2 18 " area above the slab with out any seal offs. would you agree or disagree.
Thanks

Actually 513.8(A) says the underground portion must use a wiring method suitable for Division 1. That sends you back to 501.10(A)(1). You are probably using 501.10.(A)(1)(a) Exception. But it requires concrete encasement which you didn't mention in the OP.

In addition, 513.8(B) considers the entire underground run to be in the classified location, which means that ?? raceways embedded in the hangar floor or buried below the floor are considered to be in a hazardous (classified) location above the floor. Raceways that rise out of the floor in unclassified locations must be provided with boundary seals in accordance with 501.15.? (Taken from the 2005 NEC handbook)

What I didn't say, and probably should have, is that the OP installation would probably have been acceptable in almost any other application - and it probably SHOULD be acceptable in this case too, in my opinion, but isn't.

Article 514 is largely extracted from and/or reflects the position of the Technical Committee (TC) for NFPA 409-2004, Standard on Aircraft Hangars. There are certain ?political? considerations that must be observed when multiple TCs have detailed overlapping scopes.

Most TCs (both inside and outside of NFPA) consider ?filled? below grade locations to be to be unclassified; however some consider it to be Division 1 if it is directly below a classified location. Sound arguments may be made for either case; however the one thing it cannot be is Division 2. I personally lean toward the unclassified position simply from its historic success.

 

[dennis schaffert]

hanger

hanger

I recently encountered a similar situation in a classified area and I believe that the interpretation of( passing through) is some times misunderstood for instance take a square room that is classified, as i interpreted it, I could pass a conduit feeding some other apparatus on the outside, of an opposite wall directly through the classified area if I had no box's or terminations landing in that area and not be required to seal off. but in this instance we have a termination with in the area requiring seal offs Passing through would require nothing more than couplings, rigid , with at least five full threads engaged no possibility of migration of dangerous gas or fumes exist in this instance. it is when you place an enclosure, device, or termination that opens up the possibility of migration

 

[chris kennedy]

just remember that the percentage of fill for a seal of is 25 %

New to this. As per NEC?

 

[rbalex]

"Run through" means just that - couplings aren't permitted either - See Section 501.15(A)(1)(4) Exception 1.

UL permits RMC and IMC to be manufactured in any length. 10' is standard but I've seen 24' sticks.

 

[rbalex]

See 501.15(C)(6). Most manufacturers now make "specifically identifed" units.

 

[dennis schaffert]

passing through

passing through

Bob
You are correct I read the section and not even a coupling can be used when passing through. You are very sharp and have my respect
Dennis