Electrical enclosures are rated based on their ability to withstand a varying degree of environmental elements, including dust, water, and ice. In the United States, the National Electrical Manufacturers Association developed the NEMA rating for classifying an enclosure’s level of protection from those environmental elements.
The International Electrotechnical Commission (IEC) http://www.iec.ch/index.htm has developed an alternative rating system, the IP standard, which stands for Ingress Protection.
The standard format is “IP’ followed by two numbers which designate the level of protection. The first digit, which ranges from 1-6, specifies the level of protection from solids, and the second digit, which ranges from 1-8, specifies the level of protection from water.
The higher the number is, the greater the level of protection. For instance, an enclosure with a rating of IP10 would offer less protection than an enclosure that is rated at IP54.
The following table summarizes the various IP number designations
NEMA vs IP Ratings Table
There is not a direct correlation between NEMA ratings and IP ratings, as the two systems are based on a different set of variables. However, the table below shows an approximate cross reference that can be used to help determine the IP number that meets or exceeds a particular NEMA rating.