Wednesday, January 22, 2014

NEMA (National Electrical Manufacturers Association) Classifications for Limit Switches

limit switch enclosure
Choose the right Limit Switch enclosure
Limit switch enclosures carry classifications for tightness and protection from external environments. The National Electrical Manufacturers Association (NEMA) maintains these classifications.

Here is a listing of the most typical NEMA classifications for limit switches. The definition below are from the NEMA site and the entire document can be seen here.


Type 4 Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); and that will be undamaged by the external formation of ice on the enclosure.

Type 4X Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); that provides an additional level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.

Type 7 Enclosures constructed for indoor use in hazardous (classified) locations classified as Class I, Division 1, Groups A, B, C, or D as defined in NFPA 70.

Type 9 Enclosures constructed for indoor use in hazardous (classified) locations classified as Class II, Division 1, Groups E, F, or G as defined in NFPA 70.

In Hazardous Locations, when completely and properly installed and maintained, Type 7 enclosures are designed to contain an internal explosion without causing an external hazard. Type 9 enclosures are designed to prevent the ignition of combustible dust. 

You should always consult with an application engineer before choosing the limit switch enclosure for your application.

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