Black Box Explains...NEMA Ratings for Enclosures

The  National Electrical Manufacturers’ Association (NEMA) issues guidelines  and ratings for an enclosure’s level of protection against contaminants  that might come in contact with its enclosed equipment.

There are many numerical NEMA designations; we’ll discuss NEMA  enclosures relevant to our on-line catalog: NEMA 3, NEMA 3R, NEMA 4,  NEMA 4X, and NEMA 12.

NEMA 3 enclosures, designed for both indoor and outdoor use, provide  protection against falling dirt, windblown dust, rain, sleet, and snow,  as well as ice formation.

The NEMA 3R rating is identical to NEMA 3 except that it doesn’t specify protection against windblown dust.

NEMA 4 and 4X enclosures, also designed for indoor and outdoor use,  protect against windblown dust and rain, splashing and hose-directed  water, and ice formation. NEMA 4X goes further than NEMA 4, specifying  that the enclosure will also protect against corrosion caused by the  elements.

NEMA 12 enclosures are constructed for indoor use only and are designed  to provide protection against falling dirt, circulating dust, lint,  fibers, and dripping or splashing noncorrosive liquids. Protection  against oil and coolant seepage is also a prerequisite for NEMA 12  designation.