Published on: January 13, 2012 by Blair Haas
Perhaps one of the most confusing standards for an engineer to follow is NEMA ratings as it relates to enclosures. It would be natural to consider that the higher the NEMA rating, the greater the protection. This is definitely not the case. It is also typical that one might assume that having a NEMA rating of any sort implies a high level of protection. This is also not the case. NEMA ratings are set up in a way to address a variety of concerns: safety from moving parts, protection from dripping water, dripping oils, sprayed liquids, UV, corrosion, ice, and many more. NEMA 1 ratings, for example, simply suggest that the product protects against contact with moving internal parts. The ratings becomes confusing when you consider that NEMA 4 protects your product from sprayed water, ideal for wash-down or weather intensive locations. NEMA 12 only protects against dust, falling dirt and dripping liquids so would be more appropriate in an environment where there may be less significant environmental factors, such as a factory which may not be a clean room. NEMA 3 is weather resistant, with NEMA 3r protecting against icing as well. The point is that you want to be sure you are receiving the level of protection you need without overpaying for too much. For a complete listing of all of the relevant NEMA ratings for enclosures, Bud has a great tool, the Design Tips Handbook which you can download for free. Good luck with your design!