Class 1 Underground Conduits

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501.10(A)(1)(a) Exception allows PVC underground in Class 1 Division 1 Location if encased in concrete and buried 2' deep
501.10(B)(1)(1) leaves the same rule in place for Class 1 Division 2
These two code sections would suggest that the boundary that declassifies these classified locations is not limited by depth of conduit

When can we use PVC without encasing in concrete under Class 1 locations?

511.3 for commercial garages says that the Class 1 location does not extend beyond solid partitions. It does not mention concrete floors, but are they implied?
Since 511 does not address underfloor conduits or wiring methods , I assume we refer back to 501. We have inspectors that go either way on commercial garages because the code is confusing ( not clear).
What is the intent? Can we use PVC under the floor in Commercial garages? Is there a depth limitation? Is there a concrete encasement requirement?

If the area under the floor is not classified ( which is not clarified by code?) , then we can penetrate the floor with a piece of GRC that extends without fittings to above the 18" (Classified level) without a requirement for seal offs. But if the area under the floor is classified, we need seal offs because we are entering the classified location? Are seal offs required for all floor penetrations in Commercial garages?

I believe the code needs some rewriting in 511?

I am clear that none of this is a question in 514 outside locations, but that code does not apply to 511 inside locations.
 

rbalex

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Mission Viejo, CA
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Professional Electrical Engineer
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When can we use PVC without encasing in concrete under Class 1 locations?
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For Division 1, there is an "exception" within the Exception:"...The concrete encasement shall be permitted to be omitted where subject to the provisions of 514.8 Exception No.2. and 515.8(A). ..." . See Section 501.10(B)(1)(6) for Division 2.

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511.3 for commercial garages says that the Class 1 location does not extend beyond solid partitions. It does not mention concrete floors, but are they implied?
Since 511 does not address underfloor conduits or wiring methods , I assume we refer back to 501. We have inspectors that go either way on commercial garages because the code is confusing ( not clear).
What is the intent? Can we use PVC under the floor in Commercial garages? Is there a depth limitation? Is there a concrete encasement requirement?
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The Code is clear enough; if it doesn't say it is classified, it isn't. Unless dispensing is included, the underground is not classified for commercial garages.

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If the area under the floor is not classified ( which is not clarified by code?) , then we can penetrate the floor with a piece of GRC that extends without fittings to above the 18" (Classified level) without a requirement for seal offs
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Yes

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But if the area under the floor is classified, we need seal offs because we are entering the classified location? Are seal offs required for all floor penetrations in Commercial garages?
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Only where Article also 514 applies.

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I believe the code needs some rewriting in 511?
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You will need to convince the NFPA 30A Technical Committee first.
 
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