NEMA 7/9 Enclosure in Group B Area

[Hankj]

Hi, long time lurker, first time poster here.

We have an area that we have classified as Class I, Div. 2, Group B. This system is outdoors. We had a 3rd party do a review of the system and he called out an explosion proof enclosure because the UL name plate only specified Group C & D. The gentlemen tasked with remedying this issue believes no change is necessary because the manufacturer calls this enclosure NEMA 7/9, in their datasheet (no NEMA stamp on the enclosure). He has NEMA documentation stating NEMA 7/9 is rated for Group B and the nameplate says it is "RAINTIGHT".

In my opinion, it should be replaced simply for the indoor rating, no questions asked. Also, from my knowledge of the code and reading this forum regarding similar questions, the NEMA 7/9 rating does us no good if UL or another NRLT did not test and label this particular product for Group B. One question still remains in my mind, how can the manufacturer call this enclosure NEMA 7/9 if it does not meet the specifications that NEMA claims?

I would appreciate any comments or feedback regarding my assessment and additional talking points to help the folks not as familiar with the code. Thanks

 

[don_resqcapt19]

The enclosure requires a nameplate with the marking that includes the Class, Division and Group that the enclosure is rated for. Just NEMA 7/9 does not tell me anything I need to know. 500.8(B)(1) requires the equipment to be listed for the group.
Most explosionproof enclosures you find are only marked for Groups C & D. You have to be careful when you have a Group A or B area to get the equipment suitable for the area. A Group C and D enclosure may not contain the explosion of a Group B product within the enclosure.

If you have some specific products, the exceptions to 500.6(A)(2) may permit the use of the enclosure marked for Groups C and D.

 

[Hankj]

The enclosure requires a nameplate with the marking that includes the Class, Division and Group that the enclosure is rated for. Just NEMA 7/9 does not tell me anything I need to know. 500.8(B)(1) requires the equipment to be listed for the group.
Most explosionproof enclosures you find are only marked for Groups C & D. You have to be careful when you have a Group A or B area to get the equipment suitable for the area. A Group C and D enclosure may not contain the explosion of a Group B product within the enclosure.

If you have some specific products, the exceptions to 500.6(A)(2) may permit the use of the enclosure marked for Groups C and D.

Good, sounds like I'm on the right track then. Thanks for pointing out the exceptions. In our case, it doesn't apply, but still good to know.

 

[petersonra]

Take a very careful look at 501.10(B)(4), especially where it references some other parts of the code.

Also take a close look at what the definition of "approved" and "identified" means.

I would also point out that NEMA standards are not the same thing as being listed. A manufacturer can claim they meet NEMA enclosure standards without it being listed by any NRTL.