Standards For Enclosures
Enclosures do not normally protect devices against conditions such as condensation, icing, corrosion, or contamination which may occur within the enclosure or enter via the conduit or unsealed openings. Users must make adequate provisions to safeguard against such conditions, and satisfy themselves that the equipment is properly protected. The National Electrical Manufacturers Association has developed the following standards:
NEMA Type 1
Type 1 enclosures are intended for indoor use primarily to provide a degree of protection against contact with the enclosed equipment in locations where unusual service conditions do not exist.
NEMA Type 3R
Type 3R enclosures are intended for outdoor use primarily to provide a degree of protection against falling rain, sleet, and external ice formation. They are designed to meet rod entry, rain, external icing, and rust-resistance design tests.
NEMA Type 3R, 7 & 9 Unilock Enclosure for Hazardous Locations
This enclosure is of cast aluminum alloy with a baked paint coating on the outside for extra corrosion resistance. The V-Band permits easy removal of the cover for inspection and for making field modifications. This enclosure is for similar applications and is designed to meet the same test as NEMA Types 3R, 7 and 9. For NEMA Type 3R applications, it is necessary that a drain be added.
NEMA Type 4
Type 4 enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, and hose-directed water and external ice formation.
NEMA Type 4X Non-Metallic, Corrosion-Resistant
Type 4X enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, and hose-directed water. Enclosure is manufactured with a synthetic rubber gasket between cover and base. Ideal for such industries as chemical plants and paper mills.
NEMA Type 7 for Hazardous Gas Locations
Type 7 enclosures are for indoor use in locations classified as Class 1, Groups C or D, as defined in the National Electrical Code. Type 7 enclosures are designed to be capable of withstanding the pressures resulting from an internal explosion of specified gases, and contain such an explosion sufficiently that an explosive gas-air mixture existing in the atmosphere surrounding the enclosure will not be ignited.
NEMA Type 9
Type 9 enclosures are intended for indoor use in locations classified as Class II, Groups E or G as defined in the National Electrical Code. Type 9 enclosures are designed to prevent the entrance of dust. Enclosed heat generating devices are designed not to cause external surfaces to reach temperatures capable of igniting or discoloring dust on the enclosure or igniting dust-air mixtures in the surrounding atmosphere.