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In North America, NEMA, UL, and CSA are the organizations commonly recognized. Their ratings are based on similar application descriptions and expected performance. UL and CSA both require enclosure testing by qualified evaluators in their labs.They also send site inspectors to make sure a manufacturer adheres to prescribed manufacturing methods and material specifications. NEMA, on the other hand, does not require independent testing and leaves compliance completely up to the manufacturer.
North American enclosure rating systems also include a 4X rating that indicates resistance to corrosion.This rating is based on the enclosure’s ability to withstand prolonged exposure to salt water spray. While a 4X rating is a good indicator that an enclosure can resist corrosion, it does not provide information on how a specific corrosive agent will affect a given enclosure material. It is best to conduct a full analysis of the specific application and environment to determine the best enclosure choice.
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In Europe, IEC ratings are based on performance criteria similar to NEMA. Nevertheless, there are differences in how enclosure performance is interpreted. For example, UL and CSA test requirements specify that an enclosure fails the watertight test if even a single drop of water enters the enclosure. In the IEC standards for each protection level (IP) a certain amount of water is allowed to enter the enclosure.
IEC does not specify degrees of protection against risk of explosions or conditions such as moisture or corrosive vapors. NEMA, on the other hand, does specify for most environmental conditions. For this reason, and because the tests and evaluations for other characteristics are not identical, the IEC enclosure classification designations cannot be exactly equated with NEMA enclosure
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