The National Electrical Manufacturers Association (NEMA) maintains a number of standards for electrical components. Architects are often asked to select a component that has a NEMA enclosure type. Those enclosure types are listed below and are based on NEMA Standards Publication 250-2003.
This article is adapted from the official NEMA Enclosure Types PDF. Please refer to that PDF for more detail.
Non-Hazardous Locations
NEMA Type 1: For indoor use. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of falling dirt.
NEMA Type 2: For indoor use. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of falling dirt. Provides a degree of protection to internal components from the harmful effects of dripping or lightly slashing water.
NEMA Type 3: For indoor or outdoor use. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of falling dirt and blowing dust. Provides a degree of protection to internal components from the harmful effects of the ingress of rain, sleet, or snow. Will not be damaged by the formation of ice on the exterior of the enclosure.
NEMA Type 3R: Same as NEMA Type 3 except does not protect against wind blown dust.
NEMA Type 3S: Same as NEMA Type 3 except external mechanisms will remain operable when the enclosure is ice laden.
NEMA Type 3X: Same as NEMA Type 3 except it provides an additional level of protection from corrosion.
NEMA Type 3RX: Same as NEMA Type 3 except it provides an additional level of protection from corrosion but does not protect against wind blown dust.
NEMA Type 3SX: Same as NEMA Type 3 except it provides an additional level of protection from corrosion and external mechanisms will remain operable when the enclosure is ice laden.
NEMA Type 4: For indoor or outdoor use. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of falling dirt and blowing dust. Provides a degree of protection to internal components from the harmful effects of the ingress of rain, sleet, snow, splashing water, and hose directed water. Will not be damaged by the formation of ice on the exterior of the enclosure.
NEMA Type 4X: Same as NEMA Type 4 except it provides an additional level of protection from corrosion.
NEMA Type 5: For indoor use. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of solid objects including falling dirt, circulating dust, fibers, lint, or other small non-flammable objects. Provides a degree of protection to internal components from the harmful effects of dripping or lightly slashing water.
NEMA Type 6: For indoor or outdoor use. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of falling dirt. Provides a degree of protection against the negative effects of ingress of hose directed water or occasional, temporary, shallow submersion in water. Will not be damaged by the formation of ice on the exterior of the enclosure.
NEMA Type 6P: Same as NEMA Type 6 except provides a degree of protection during prolonged, shallow submersion in water.
NEMA Type 12: For indoor use. Provided without knockouts. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of falling dirt, circulating dust, fibers, lint, or other small non-flammable objects. Provides a degree of protection to internal components from the harmful effects of dripping or lightly slashing water.
NEMA Type 12K: Same as NEMA Type 12 except it is provided with knockouts.
NEMA Type 13: For indoor use. Provides a degree of protection to personnel against hazardous internal parts. Provides a degree of protection to internal components from the ingress of falling dirt, circulating dust, fibers, lint, or other small non-flammable objects. Provides a degree of protection to internal components from the harmful effects of dripping or lightly slashing water. Provides a degree of protection against the spraying, splashing, and seepage of oil and non-corrosive coolants.
Hazardous Locations
NEMA Type 7: Enclosures constructed for indoor use in hazardous locations classified as Class I, Division 1, Groups A, B, C, or D as defined in NFPA 70.
NEMA Type 8: Enclosures constructed for either indoor or outdoor use in hazardous locations classified as Class I, Division 1, Groups A, B, C, and D as defined in NFPA 70.
NEMA Type 9: Enclosures constructed for indoor use in hazardous locations classified as Class II, Division 1, Groups E, F, or G as defined in NFPA 70.
NEMA Type 10: Enclosures constructed to meet the requirements of the Mine Safety and Health Administration, 30 CFR, Part 18.
