NEMA 250 2014 Edition, January 1, 2014
Enclosures for Electrical Equipment (1000 Volts Maximum)
Published By:National Electrical Manufacturers Association (NEMA)
This standard covers enclosures for electrical equipment rated not more than 1000 Volts and intended to be installed and used as follows:
a. Non-hazardous (unclassified) locations:
1) Enclosures for indoor locations, Types 1, 2, 5, 12, 12K, and 13; and,
2) enclosures for indoor or outdoor locations, Types 3, 3X, 3R, 3RX, 3S, 3SX, 4, 4X, 6, and 6P.
b. Hazardous (classified) locations:
1) Enclosures for indoor locations, Types 7 and 9;
2) Enclosures for indoor or outdoor locations, Type 8; and,
3) Enclosures for mining applications, Type 10. Requirements for enclosures for non-hazardous (unclassified) locations are contained in the body of the standard.
Requirements for enclosures for hazardous (classified) locations are contained in Annex A of the standard.
This standard covers the requirements to provide protection to the enclosed equipment against specific environmental conditions.
This standard supplements requirements for enclosures that are contained in the individual product standards. This standard does not cover the requirements for protection of the enclosed equipment against conditions such as condensation, icing, corrosion, or contamination, which may occur within the enclosure or which may enter via conduit or unsealed openings.
A product that contains features, characteristics, components, materials, or systems new or different from those in use when the standard was developed, and that involves a risk of fire, electric shock, or injury to persons shall be evaluated using the appropriate additional component and end-product requirements as determined necessary to maintain the level of safety for the user of the product as originally anticipated by the intent of this standard.