Class 1 Division 2 NEMA Ratings

[Bill Conner]

We are having a difference of opinion with an engineering firm concerning NEMA Ratings of equipment in Class 1 Division 2 areas.

In section 501.105 what NEMA ratings are permitted in a Class 1 Division 2 area?

We have assumed from past experience NEMA 3, 3R, 4, 4X, and 12 are permissible and have passed electrical inspections at various sites.

Please comment.

Thanks
Bill Conner

 

[rbalex]

It depends. The general rule is found in Section 501.10(B)(4). The "Types" you listed are consistent with the general rule; however, enclosures that contain arcing, sparking, or high-temperature components may require explosionproof enclosures in Class I, Division 2 as specified in Sections 501.105 (B)(1), 501.115(B)(1), and 501.150(B)(1). There are also other acceptable non-explosionproof protection techniques identified in Section 500.7.

 

[retirede]

It depends on what’s in the enclosure. If it contains non-hermetically sealed contacts that are not wired to intrinsically safe circuits, a NEMA 7 enclosure is likely required.

There are other options such as inert gas purge that can allow a lesser enclosure rating in these cases.

 

[Jraef]

Ah, those pesky little details...