In manufacturing, there are two standards used to measure the different grades of electrical enclosures and how resistant they are to the ingress of certain materials. NEMA ratings and IP ratings both define degrees of protection against substances such as water and dust, but use different test methods and parameters to define their enclosure types (NEMA 250 and IEC standard 60529).
NEMA, refers to the National Electrical Manufacturers Association, a trade association whose membership is comprised of electrical equipment manufacturers in the United States, and is responsible for publishing a wide range of standards, including not only enclosure integrity but also electrical connections.
For example, a device with a NEMA 4 rated enclosure must provide a degree of protection against the following:
IP ratings are a part of the International Electrotechnical Commission (IEC). “IP” stands for “international protection” but is commonly referred to as “ingress protection.” There are dozens of IP standards, but some of the most common ones are:
The first digit represents the degree of protection against solid objects, while the second digit covers protection against water.
NEMA is geared towards industrial applications and is primarily used in North America, whereas IP ratings cover a broad set of applications worldwide. IP ratings cover protection only against the ingress of water and solid objects while NEMA includes supplementary protection standards against corrosion resistance and icing. NEMA ratings also include distinctions between hazardous and non-hazardous environments.
While there is no direct conversion between NEMA and IP they can be compared as shown in the table below.
Ingress protection requirements for enclosures are defined in the codes and standards for various explosion protection options as follows:
Purge & pressurization (Ex p): BS/EN 60079-2: Minimum IP40; NFPA496 (2021) NEMA 3, 3S, 4, 4X, 6, 6P, 12, 13 (X-purge only)
Increased safety (EX e): BS/EN 60079-7: Minimum IP54
Type n protection (Ex nR): BS/EN0079-15 Minimum IP66 (plus breathing test).