Class I Group Classifications

[msb10]

One of the mechanical engineers where I work is specifying a piece of equipment that is (apparently) available as either Class I Group C or as Class I Group D. I've seen devices with a rated Group C and D, but this one is either one or the other. I don't know many more details, since I wasn't there for the conversation, but the advice he got from one of our electrical engineers was that Group C is "more hazardous", so he should get the equipment rated Class I Group C, and he would be covered in both.

I can understand this opinion. Looking at the descriptions, Groups B through D allow progressively larger safe gaps, so I guess you could interpret that a group B device could be installed in a group C location, if you wanted to. I just can't find anywhere in Article 500 that lets you install a group C device in a group D environment.

My feeling is that only a device listed for group D should be installed in a group D location. Can anyone offer any guidance, either to support my opinion or to convice me that I'm wrong, and this is ok?

Thanks,

Matt

 

[rbalex]

The principal rule is 500.8(A)(1) with applicable secondary rules in 500.8(B); especially 500.8(B)(3).

I haven?t seen a product that is listed for Group C that isn?t also listed for Group D either and I can?t quite imagine why it wouldn?t be; nevertheless it isn?t necessary.

The key is the word identified in 500.8(A)(1). Identified is a defined term in Article 100:

Identified (as applied to equipment). Recognizable as suitable for the specific purpose, function, use, environment, application, and so forth, where described in a particular Code requirement.

FPN: Some examples of ways to determine suitability of equipment for a specific purpose, environment, or application include investigations by a qualified testing laboratory (listing and labeling), an inspection agency, or other organizations concerned with product evaluation.

Note it doesn?t say the equipment must be listed or labeled.

CMP14 went through a major effort during the 2002 cycle to carefully select those items of equipment that must specifically be listed or labeled for Classified locations versus equipment that needs only to be ?recognized as suitable??

The problem is the ?Marking? requirement in 500.8(B)(3). It is very specific.

So do you really need Group C equipment? If not get, the Group D equipment and don?t look back. If you had a location with both Group C and D then I would get the Group C equipment and make my case with the AHJ.

 

[msb10]

Thank you very much. That's a big help.

Regards,

Matt