Interpretations of NEMA Type 12 enclosures

[Ibsft]

I?ve already read many of the posts about NEMA 12 enclosures on this forum and have learned a lot of good info. Thank you! :thumbsup:

My old (and limited) understanding of a NEMA 12 enclosure was that it was for oily environments and that the enclosure was essentially liquid tight. With the popularity of VFDs and the need to deal with their heat output I have seen enclosures claiming to be NEMA 12 with open vents protected only by a coarse see through material. Others have had vents with paper filters similar to furnace filters. Neither seems ideal for an oily environment and by my old understanding would not be acceptable as a type 12 enclosure.

After reading the current ?degree of protection? language I do not know how one can decide when something meets the intent of the rating, specifically NEMA Type 12. A manufacturer or panel builder can claim the coarse foam will offer a ?degree of protection? against light splashing, but imo that is really pushing it.

What say the experts on this subject, how/where does one draw the line between what is true type 12 and what is not?

 

[petersonra]

NEMA types are somewhat obsolete. Those were self certified standards and did not mean all that much.

These days it is type 12 if UL says it is. It just has to pass the tests that are required to be listed by UL as a type 12 enclosure.

Course filters won't cut it but there are filters UL has tested that do meet the type 12 criteria.

 

[Jraef]

NEMA types are somewhat obsolete. Those were self certified standards and did not mean all that much.

These days it is type 12 if UL says it is. It just has to pass the tests that are required to be listed by UL as a type 12 enclosure.

Course filters won't cut it but there are filters UL has tested that do meet the type 12 criteria.

That pretty much sums it up. I'll just add that what you may have witnessed is sort of a marketing trick employed by people taking advantage of the confusion that exists because of the change in what "Type 12" means. If I don't care about my reputation, I can refer to my screen door as NEMA Type 12 and its up to you, the consumer to accept or reject that claim by buying it or not buying it. But if I send it to an unrelated third party testing agency, such as UL for a Type 12 listing under the standards of UL50 for electrical enclosures, it will fail. The standards are the same, the difference is that there is no required testing for making a NEMA 12 claim, it's an honor system. That's why UL stepped in. So when companies claim NEMA 12 on a vented VFD enclosure, but it's obvious that it's going to leak, it's not likely UL listed as Type 12. If you look at their UL file, you might see the drive UL listed as open type and type 1 only. Most people never take it that far, but AHJs who are savvy to this will.

That said, Type 12 is defined as indoor industrial use, dust tight, drip resistant. It's not required to stand up to anything more than water dripping on it from above, it's not that difficult to meet that criteria. The bigger problem with venting the box is the amount of dust that gets it. The filter has to actually work to the test standards, which within UL50 define the partcle size etc.