nema 12 enclosure
- Thread starter Shaun B
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- Wisconsin
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- PE (Retired) - Power Systems
No.
A NEMA 12 enclosure is not tested for having liquid 'pool' against the gasket. There is no requirement for NEMA 12 paint to be UV resistant.
Most manufacturers do make a drip hood for their NEMA 12 enclosures, but they are still probably only listed for indoor use.
Most manufacturers do offer a NEMA 3/12 dual rated enclosure family, that many people generically still call NEMA 12.
A NEMA 12 enclosure is not tested for having liquid 'pool' against the gasket. There is no requirement for NEMA 12 paint to be UV resistant.
Most manufacturers do make a drip hood for their NEMA 12 enclosures, but they are still probably only listed for indoor use.
Most manufacturers do offer a NEMA 3/12 dual rated enclosure family, that many people generically still call NEMA 12.
stew
Senior Member
- Location
- federal way,washington
Nema 12 enclosures are not listed for oudoor use regardless of what is speced. The spec is incorrect as it pertains to code . Nema 12 encolsures are indoor and protect against entry of solid substances dirt, dust etc. They are also rated to withstand some incidental splashing but are not to be used in outdoor wet location. Indoor use only.
renosteinke
Senior Member
- Location
- NE Arkansas
I see that there is some confusion as to what 'NEMA 12' means.
NEMA 12 is defined as 'oil tight.' That's why they have gaskets - to keep oil from seeping into the enclosure. I defy anyone to make a gasket that will keep oil oit, but will let dirt and dust pass through.
It's no accident that very many NEMA-12 enclosures are also rated for NEMA-4. In practical terms, the only difference between the two tests is that for NEMA 12, the oil is not directed at the enclosure as a pressurised stream, and that many NEMA 4 gaskets are dissolved by contact with oil. These are fine points; with readily availably materials, it's pretty hard to make a NEMA-12 enclosure that's not also NEMA-4 rated, and vise-versa. Again, in practical terms, the difference (if there is one) will be that a NEMA-12 will have a door with a handle, while a NEMA-4 will have little clamps.
Keep in mind that simply being outside does not mandate a NEMA-4 enclosure. Adding a little top shield -indeed, the very design of the flange around the door - might be more than enough to provide a NEMA-3R rating.
As for the sunlight resistance of the paint ... huh? All enclosures these days - even NEMA-1 - are required to have more than just paint for corrosion protection. The difference in 'weathering' tests between NEMA-1 and NEMA-3 (or 4) is pretty minor; I can't recall ever seeing a testing failure that had anything to do with the base material. With regards to pre-punches, NEMA-12 and NEMA-4 standards are alike.
NEMA-4X is something completely different.
"Outside" isn't the only criteria. If oil is a concern, then NEMA-12 is a requirement - in addition to whatever other requirements are imposed by the environment.
NEMA 12 is defined as 'oil tight.' That's why they have gaskets - to keep oil from seeping into the enclosure. I defy anyone to make a gasket that will keep oil oit, but will let dirt and dust pass through.
It's no accident that very many NEMA-12 enclosures are also rated for NEMA-4. In practical terms, the only difference between the two tests is that for NEMA 12, the oil is not directed at the enclosure as a pressurised stream, and that many NEMA 4 gaskets are dissolved by contact with oil. These are fine points; with readily availably materials, it's pretty hard to make a NEMA-12 enclosure that's not also NEMA-4 rated, and vise-versa. Again, in practical terms, the difference (if there is one) will be that a NEMA-12 will have a door with a handle, while a NEMA-4 will have little clamps.
Keep in mind that simply being outside does not mandate a NEMA-4 enclosure. Adding a little top shield -indeed, the very design of the flange around the door - might be more than enough to provide a NEMA-3R rating.
As for the sunlight resistance of the paint ... huh? All enclosures these days - even NEMA-1 - are required to have more than just paint for corrosion protection. The difference in 'weathering' tests between NEMA-1 and NEMA-3 (or 4) is pretty minor; I can't recall ever seeing a testing failure that had anything to do with the base material. With regards to pre-punches, NEMA-12 and NEMA-4 standards are alike.
NEMA-4X is something completely different.
"Outside" isn't the only criteria. If oil is a concern, then NEMA-12 is a requirement - in addition to whatever other requirements are imposed by the environment.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I did not mean to limit the UV protection only to paint, (i.e. gasketing material may also by subject to harm from UV).
stew
Senior Member
- Location
- federal way,washington
The Nema book says that Nema 12 enclosures are designed to be used indoors period. I dont know haw you get past that sentence in the Nema book regardless of what kind of dress you put on the pig. Its still an indoor pig. Definition of this enclosure come from NEMA 250-2003 Definitions.
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- Location
- Illinois
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- retired electrician
The NEMA 12 enclosures that I use all have the same clamps as the NEMA 4. The difference is that the NEMA 12 only has clamps on the side opposite the hinge and the NEMA 4 has clamps on the other two sides in addition to the one opposite the hinge. Also on the larger enclosures there will be more clamps along a side on a NEMA 4 as compared to a NEMA 12. I assume that the extra clamps are needed to meet the "pressurized stream" test.
That is the reason I was given by a manufacturer's rep. In the case of water, the lack of a shield allows the water to "pool" as mentioned and if it then freezes the gasket and enclosure integrity are compromised.
zog
Senior Member
- Location
- Charlotte, NC
renosteinke
Senior Member
- Location
- NE Arkansas
"still an indoor pig."
You miss the point.
If you're making an academic argument that a NEMA 12 rating has no relation to indoor / outdoor use, you're correct. For that matter, an "explosion proof" (Nema 9) rating has absolutely nothing to do with the indoor / outdoor rating. Heck, you really get down to it, even NEMA-3R and NEMA-4 ratings have nothing to do with 'indoor' or 'outdoor' applicatiuons.
You have to look at the testing criteria, and choose the location that apply. NEMA-3R is tested against an artificial rain at a certain angle; we equate this to being outdoors in a wet location. NEMA-4 gets a stream of water applied at every angle possible. NEMA-12 gets oil dripped on it, and the oil isn't supposed to enter.
If you want to get technical aboput it, it's very possible for a location to require enclosures to be both NEMA 12 and NEMA 4.
But that's just armchair philosophy in so many instances. In practical terms, the same methods are used to meet each of the challenges. It's pretty hard to make an enclosure that meets only one, but not the other two as well. Chances are, those little drip shields are more a response to customer demand than a necessity for the enclosure to actually pass the test. Yet, when you look back at the test - "rain" at a slight angle - that little piece of sheet metal may be all that's needed to make a NEMA-1 enclosure pass the NEMA-3R test.
Look again at those NEMA-12 enclosures. Gaskets aside, you'll likely find a flange that forms a gutter around the door opening. Then go look at the door of your car. Do you see a similar gutter (though cars have the gutter on the door itself?) Do you think that gutter can tell the difference between water and oil?
I wouldn't worry too much over the fine print.
You miss the point.
If you're making an academic argument that a NEMA 12 rating has no relation to indoor / outdoor use, you're correct. For that matter, an "explosion proof" (Nema 9) rating has absolutely nothing to do with the indoor / outdoor rating. Heck, you really get down to it, even NEMA-3R and NEMA-4 ratings have nothing to do with 'indoor' or 'outdoor' applicatiuons.
You have to look at the testing criteria, and choose the location that apply. NEMA-3R is tested against an artificial rain at a certain angle; we equate this to being outdoors in a wet location. NEMA-4 gets a stream of water applied at every angle possible. NEMA-12 gets oil dripped on it, and the oil isn't supposed to enter.
If you want to get technical aboput it, it's very possible for a location to require enclosures to be both NEMA 12 and NEMA 4.
But that's just armchair philosophy in so many instances. In practical terms, the same methods are used to meet each of the challenges. It's pretty hard to make an enclosure that meets only one, but not the other two as well. Chances are, those little drip shields are more a response to customer demand than a necessity for the enclosure to actually pass the test. Yet, when you look back at the test - "rain" at a slight angle - that little piece of sheet metal may be all that's needed to make a NEMA-1 enclosure pass the NEMA-3R test.
Look again at those NEMA-12 enclosures. Gaskets aside, you'll likely find a flange that forms a gutter around the door opening. Then go look at the door of your car. Do you see a similar gutter (though cars have the gutter on the door itself?) Do you think that gutter can tell the difference between water and oil?
I wouldn't worry too much over the fine print.
stew
Senior Member
- Location
- federal way,washington
The problem is the inspectors in my area look under the skirt of the pig and find the words "indoor use" and they write cute little correction notice
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- Windsor, CO NEC: 2017
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- Service Manager
John: re-read 110.3 please. We can't override a listing in the field, regardless of how smart we are.
stew
Senior Member
- Location
- federal way,washington
Thats what I was getting at. It is interesting and all that how the testing is done and how ell these enclosures work. Just the verbage by the manufacturer as given by NEMA is what we need to go by in the field.
I just wanted to comment on part of reinosteinke's quotes pertaining to testing of enclosures. We only specify UL Type rated enclosures as they are fully tested for their Type rating and a majority of our customers require the UL rating. The fact that an enclosure is NEMA rated does not mean that it has been fully tested for the rating. It means that the manufacturer is stating that it will meet the enclosure Type rating requirements, whatever they may be. This is my understanding and I could be wrong.
petersonra
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- Location
- Northern illinois
- Occupation
- engineer
These days there are enclosures that are dual rated 12 and 4, and that is usually what I use.
UL lists enclosures according to UL type, not NEMA type. The types roughly correspond to each other, i.e.- a NEMA type 1 and a UL type 1 enclosure are basically the same beast, but it is not a NEMA 1 enclosure just because it is UL listed as a type 1 enclosure and not a UL type 1 enclosure just because the manufacturer says it is a NEMA 1 enclosure, but usually that is the case these days.
UL lists enclosures according to UL type, not NEMA type. The types roughly correspond to each other, i.e.- a NEMA type 1 and a UL type 1 enclosure are basically the same beast, but it is not a NEMA 1 enclosure just because it is UL listed as a type 1 enclosure and not a UL type 1 enclosure just because the manufacturer says it is a NEMA 1 enclosure, but usually that is the case these days.
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