501.10(B)(7) Use of PVC

[rowlandct]

Section 501.10(B)(7) allows the use of Schedule 80 PVC conduit, elbows, and associated fittings in Class I, Div 2 locations in industrial establishments with restricted public access where the conditions of maintenance and supervision ensure that only qualified persons service the installation and where metallic conduit does not provide sufficient corrosion resistance.

Excluding boundaries, this seems straightforward for wiring methods in Class I, Div 2 areas. What happens at the boundaries? Can PVC conduit be routed through the boundaries if adequately sealed? Section 501.15(B)(2) addresses Class I, Div 2 boundaries and there are no exceptions for PVC.

Section 501.15(B)(2) states ?Rigid metal conduit or threaded steel intermediate metal conduit shall be used between the sealing fitting and the point at which the conduit leaves the Division 2 location, and a threaded connection shall be used at the sealing fitting?.there shall be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Division 2 location.

I have a situation where PVC conduit has been routed from below a floor (unclassified below the floor) into a Class 1, Div 2 location. To add a standard seal-off, a PVC/RMC coupling would need to be added between the seal and the boundary. I believe this would violate the 501.15(B)(2) ?no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Division 2 location? requirement.

If you go by 501.10(B)(7), can the 501.15(B)(2) requirements to use RMC at the boundary be ignored?

Any insights or answers to the above questions would be greatly appreciated.

Thanks in advance!

Craig

 

[rbalex]

Section 501.10(B)(7) allows the use of Schedule 80 PVC conduit, elbows, and associated fittings in Class I, Div 2 locations in industrial establishments with restricted public access where the conditions of maintenance and supervision ensure that only qualified persons service the installation and where metallic conduit does not provide sufficient corrosion resistance.

Excluding boundaries, this seems straightforward for wiring methods in Class I, Div 2 areas. What happens at the boundaries? Can PVC conduit be routed through the boundaries if adequately sealed? Section 501.15(B)(2) addresses Class I, Div 2 boundaries and there are no exceptions for PVC.

Section 501.15(B)(2) states “Rigid metal conduit or threaded steel intermediate metal conduit shall be used between the sealing fitting and the point at which the conduit leaves the Division 2 location, and a threaded connection shall be used at the sealing fitting….there shall be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Division 2 location.

I have a situation where PVC conduit has been routed from below a floor (unclassified below the floor) into a Class 1, Div 2 location. To add a standard seal-off, a PVC/RMC coupling would need to be added between the seal and the boundary. I believe this would violate the 501.15(B)(2) “no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Division 2 location” requirement.

If you go by 501.10(B)(7), can the 501.15(B)(2) requirements to use RMC at the boundary be ignored?

Any insights or answers to the above questions would be greatly appreciated.

Thanks in advance!

Craig

I have avoided answering this question because the legal answers are cheats, although it may just be a matter of interpretation, and the correct answer doesn’t currently meet Code.

You are correct that there are no Exceptions for PVC in Section 501.15(B); however, there are several Exceptions for the seal itself.

The OP wasn’t entirely clear what the “unclassified” terminus of the below floor conduit was. Is it a room below or an under-slab conduit run to some unclassified location? In any case these are two options:

• If the raceway comes from a room below, then 501.15(B)(2), Exception 2 may apply. The open item is that the room“… is unclassified as a result of pressurization into a Class I, Division 2 location…;”i.e., would the room below have been otherwise classified Division 2 had it not been pressurized. Most folks wouldn't recognize the significance of the current wording, but it is something to consider.
• If the raceway is an under-slab run or 501.15(B)(2), Exception 2 doesn’t apply, you must judiciously select the boundary. The simplest way is to install the PVC/RMC coupling and then pour a concrete pad flush with the top of the coupling. It should be a minimum of 2” around the coupling. If necessary draw an area classification detail showing the boundary is the top of the pad.