Electrical enclosures used in North America are often described using NEMA types. NEMA is the acronym for National Electrical Manufacturers Association which publishes many standards for electrical equipment. The major types are numbered 1 through 13 and they differ in the sorts of contaminants they are designed to exclude or the explosive materials they can survive. Various sorts of cabinet coolers may be needed depending on the heat generated within the cabinet, the ambient temperature, the sensitivity of the equipment in the cabinet to elevated temperatures and the type of cabinet.
All NEMA cabinet types are meant to keep people from touching hazardous parts when the cabinet is closed. Any outdoor-rated cabinet can be used indoors.
NEMA 1 is designed for indoor use with some protection for falling dirt.
NEMA 2 is same as NEMA 1 plus protection from some dripping or splashing water.
NEMA 3 all are designed for outdoor use. There are several variants:
NEMA 3 is designed for some protection from falling and windblown dust, preventing rain, sleet and snow from interfering with electrical equipment and to be undamaged by external ice.
NEMA 3R is same as 3 except not for excluding windblown dust.
NEMA 3S is same as 3 with external handles operable when icing occurs.
NEMA 3X, 3RX and 3SX are same as 3, 3R and 3S with additional corrosion resistance.
NEMA 4 is same as NEMA 3 with additional resistance to splashing water and being hosed down with water.
NEMA 4X is same as NEMA 4 with additional corrosion resistance.
NEMA 5 is same as NEMA 2 plus protection from settling dust, lint, fibers and flyings materials.
NEMA 6 is same as NEMA 4 plus allow temporary submersion at limited depths.
NEMA 6P is same as NEMA 4 plus allow prolonged submersion.
NEMA 7 is designed for indoor use and to contain explosions within the enclosure in areas with flammable gases.
NEMA 8 is same as NEMA 7 and is designed for outdoor use.
NEMA 9 is designed for indoor use and to contain explosions within the enclosure in areas with electrically conductive or combustible dusts.
NEMA 10 is designed to meet the requirements of the US Mine Safety and Health Administration.
NEMA 11 is same as NEMA 12 plus provide oil immersion for the electrical equipment.
NEMA 12 is same as NEMA 2 plus protection from settling circulating dust, lint, fibers and flyings materials and without factory-supplied knockouts (holes are field drilled or punched).
NEMA 12K is same as NEMA 12 with factory-provided knockouts.
NEMA 13 is same as NEMA 12 with additional resistance to spraying, splashing and seeping oil and other non-corrosive coolants (cutting oils).