The National Electrical Manufacturers Association (NEMA) published NEMA 250-2014 Enclosures for Electrical Equipment (1,000V Maximum).
This standard covers enclosures for electrical equipment rated not more than 1,000V and intended to be installed and used as follows:
Non-hazardous (unclassified) locations: enclosures for indoor locations, Types 1, 2, 5, 12, 12K, and 13; and enclosures for indoor or outdoor locations, Types 3, 3X, 3R, 3RX, 3S, 3SX, 4, 4X, 6, and 6P.
Hazardous (classified) locations: enclosures for indoor locations, Types 7 and 9; enclosures for indoor or outdoor locations, Type 8; and enclosures for mining applications, Type 10.
NEMA 250 covers the requirements to provide protection to enclosed equipment against specific environmental conditions. It supplements requirements for enclosures that are contained in individual product standards.
The 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.
Related NEMA Publishes NEMA MG 1-2014 'Motors and Generators' NEMA Publishes NEMA VE 2-2013 Cable Tray Installation Guidelines This edition includes the previous version’s errata and clarification of requirements of drainage and ventilation of enclosures. An amendment for NEMA 250-2014 will be published in late 2015.
NEMA 250-2014 may be purchased in electronic or hardcopy format on the NEMA website for $106.