Announcement

Collapse
No announcement yet.

Q about NEMA Ratings

Collapse
This topic is closed.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Q about NEMA Ratings

    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 Click image for larger version

Name:	box.jpg
Views:	1
Size:	86.9 KB
ID:	2381868

    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??

    #2
    Supplier does not have to pass inspection, you do.

    T110.20 says: no go.
    [COLOR="blue"]"Electricity is really just organized lightning." George Carlin


    Derek[/COLOR]

    Comment


      #3
      Originally posted by GlennH View Post
      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 [ATTACH=CONFIG]5672[/ATTACH]

      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??
      yes, it won't pass.

      http://www.nemacotech.com/nema-definitions-list.html
      Sometimes I don't know whether I'm the boxer or the bag.

      Comment


        #4
        Most Hoffman style boxes are rated NEMA 4/12.
        Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs.

        Comment


          #5
          The problem, as I understand it, is that the outdoor weather conditions will deteriorate the gasket especially when subject to water and freezing. Rain water/snow will settle around the gasket then freeze damaging the material and "breaking" the seal. The little added lip for NEMA 3R prevents that.
          It's not unusual for supply folks to sell 12 as 3R.
          At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

          Comment


            #6
            Originally posted by masterinbama View Post
            Most Hoffman style boxes are rated NEMA 4/12.
            What he said. Some type 12 boxes are also dual rated as 3R with the addition of a rain shield.
            Bob

            Comment


              #7
              Originally posted by masterinbama View Post
              Most Hoffman style boxes are rated NEMA 4/12.
              Not true.

              Hoffman makes design and Concept lines that are usually dual rated, these are normally 'tan' colored boxes.
              Their screw cover, lift off, and continuous hing versions are not regularly dual rated, these are normally 'grey' colored.
              Just because you can, doesn't mean you should.

              Comment


                #8
                Originally posted by jim dungar View Post
                Not true.

                Hoffman makes design and Concept lines that are usually dual rated, these are normally 'tan' colored boxes.
                Their screw cover, lift off, and continuous hing versions are not regularly dual rated, these are normally 'grey' colored.
                The Concept boxes I use are all gray. In fact, I have not seen any tan Hoffman box to my recollection. Certainly have never used one.
                Bob

                Comment


                  #9
                  Originally posted by petersonra View Post
                  The Concept boxes I use are all gray. In fact, I have not seen any tan Hoffman box to my recollection. Certainly have never used one.
                  My bad with the color. You are correct, I too cannot remember a Concept panel that was not grey.
                  Just because you can, doesn't mean you should.

                  Comment


                    #10
                    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.

                    Comment


                      #11
                      Originally posted by renosteinke View Post
                      In practical terms, I can't imagine how one would make such an enclosure.
                      All of the major manufactures list 'indoor only' enclosures.
                      Hoffman - Continuous Hinge - UL 508A Listed; Type 12, 13; File No. E61997,
                      Hubbell-Wiegmann - NEMA 12 single door wall mount - UL 508 Types 12 & 13
                      Rittal - Single Door Large Wallmount - UL Type 12
                      Saginaw - Clamp Fastened Single Door - UL Listed Type 12

                      I did not find one manufacturer that lists information that their 'drip hood' changes the basic enclosure rating. In fact Saginaw says this about their drip shield: "Industry Standards - (N/A)".
                      Just because you can, doesn't mean you should.

                      Comment


                        #12
                        Originally posted by jim dungar View Post
                        All of the major manufactures list 'indoor only' enclosures.
                        Hoffman - Continuous Hinge - UL 508A Listed; Type 12, 13; File No. E61997,
                        Hubbell-Wiegmann - NEMA 12 single door wall mount - UL 508 Types 12 & 13
                        Rittal - Single Door Large Wallmount - UL Type 12
                        Saginaw - Clamp Fastened Single Door - UL Listed Type 12

                        I did not find one manufacturer that lists information that their 'drip hood' changes the basic enclosure rating. In fact Saginaw says this about their drip shield: "Industry Standards - (N/A)".
                        Judging from Hoffman and the photo, I's guess that enclosure is a NEMA 12/ 13 only, and not a combination NEMA12/NEMA 4.

                        Hoffman NEMA 4 boxes with that style latch also have latches on the top and bottom of the door. Even the small boxes have 4 latches.

                        Comment


                          #13
                          Originally posted by renosteinke View Post
                          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.
                          Walk outside and take a look at your POCO meter. I'll almost guarantee it is a 3R enclosure. I'll with even more certainty say it won't pass 12.

                          Same with an outdoor breaker panel ... 3R, not 12.

                          Comment


                            #14
                            Let's forget the catalog listings, where they simply might not mention every possible enclosure type. Let's also forget what we have 'heard,' or what manufacturers have said in their catalog summaries of different enclosure types. Instead, let's look at what NEMA says:

                            NEMA defines NEMA-3R as: Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); and that will be undamaged by the external formation of ice on the enclosure.

                            NEMA defines NEMA-12 as: Enclosures constructed (without knockouts) for indoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and circulating dust, lint, fibers, and flyings); and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing).

                            Now ... what does this mean in terms of testing?

                            "Indoor use" used to infer a different level of corrosion protection. This is no longer the case; all enclosures now face exactly the same corrosion tests, unless they are specifically rated for some particular environment (such as "marine.") Indoor and outdoor enclosures have the same exposure test.

                            Please note that the NEMA-12 definition makes no mention of oil, or 'oil tight,' or 'oil seepage.' It does mention 'light splashing.' I can categorically state that the rain test for NEMA-3R, and the implied drainage requirement, are far more severe than any 'light splashing.' From that regard, NEMA-3R exceeds NEMA-12 requirements.

                            This leaves us with the issue of knockouts. Since NEMA-3R requirements place all knockouts below any live parts, and require the enclosure to not retain 'excessive' water after the rain test, I have to wonder if this difference in the specification is a cause for concern- especially if there are no factory KO's left unused after installation. Or, if the KO's are replaced with gasketed plugs.

                            Now, some have made reference to NEMA-4, whose enclosures often look very much like NEMA-12 enclosures. Note that NEMA-4 has a test where a pressurised stream of water is directed at the enclosure from every angle. It's safe to say that an enclosure that will keep hose directed water out from any angle will also keep out 'light splashing' or falling rain.


                            My point is that one cannot simply adopt the small-minded, petty attitude of 'if the sticker doesn't say just the right things, then it won't do.' One must think, as well. Nor is it the responsibility of the customer to address your ignorance.

                            The same can apply in the opposite direction; for example, one would be obligated to require additional protection in certain circumstances. For example, even a stainless steel enclosure will corrode away in a sewage pit, while a 'not corrosion resistant' cast iron one will do just fine. Go figure!

                            Comment


                              #15
                              Originally posted by renosteinke View Post
                              My point is that one cannot simply adopt the small-minded, petty attitude of 'if the sticker doesn't say just the right things, then it won't do.' One must think, as well.
                              Actually considering those boxes would be listed 110.3(B) requires us to go by the labeling on the box.

                              Comment

                              Working...
                              X