Q about NEMA Ratings

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Senior Member
So maybe the parts guy is only guilty of bad grammar. That should be no surprise to this forum.

It is correct to say that NEMA 12 and NEMA 3R are completely different ratings, each with its' own criteria. I suppose, in theory, that it might be possible to make an enclosure that would pass one and not the other.

In practical terms, I can't imagine how one would make such an enclosure. I suspect that a little research will show that the enclosure carries both ratings.

The NEMA tests have virtually no consideration of the aging of gaskets, etc. There as some rather mild corrosion tests. Indeed, were I to try to make something that really was 'indoor only,' this is where I would try to do it - though that has become more difficult since the standards were revised to require even indoor enclosures to be galvanized.

Rain hood? Probably not necessary with that gutter flange. I'd go with the manufacturers' recommendations. Likewise, it's possible that the manufacturer would suggest the addition of a small 'weep hole' in the bottom face.
I'm not sure of what you mean by "the NEMA tests". All of our control boxes are UL rated and they do require initial testing. However, to my understanding, NEMA rated boxes do not. I could be wrong, but I thought NEMA ratings basically means they "would" pass the testing for any particular rating. Like I said, I may be mistaken. :)


New User
Houston, Texas
So I needed an outdoor rated junction box, called supplier and he said sure I"ve got a NEMA 12 box right here.

Fine I said , send it out.

Got the box and then started thinking about the NEMA 12 rating and looked it up in my trusty Electrical Pal book and it says a 12 is rated for indoor use.

Hmmm, supplier says no its fine to use outdoor.:?

Here is a pic View attachment 5672

box has no knockouts, has a nice gasket and lip at door, there is no way any water is getting in this box.

Would you have a problem using this box??
Normally, NEMA 12 is constructed for mainly indoor used only, it gives protection against the ingress of dripping and light splashing water, therefore you not suppose to put it outside, it cannot protect your equipment from the rain too risky. Check this for nema 12 definition.

If you want to put it outdoor I recommend you go for NEMA 3R, 4, 4X

NEMA 3r is the cheapest one, it limits the water going inside the enclosure and will not damage the live part.
NEMA 4 is the middle one here, it will protect you from a heavy rain environment because, in order to pass type 4 criteria you have to test hose directed water, the testing method will be Fire Hose 65 gal. (246L)/min. - 5 min. Minimum and must result "no water get inside".
NEMA 4X is like type 4 but add corrosion resistance characteristic to it.
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