A guide to understanding the meaning of NEMA Ratings and what each one specifically means
North American enclosures operate with a standard of NEMA ratings for electrical enclosures, but what is NEMA? NEMA stands for The National Electrical Manufacturers Association, an organization developed to form the technical standards for the manufacturing of electrical equipment and medical imaging equipment. NEMA utilizes a standardized rating system that outlines the suitable environments for the operation of electrical enclosures and often indicates the capacity of a fixed enclosure to endure specific environmental conditions.
When trying to cool down electrical enclosures, the cooling solution will have to conform to the enclosure's NEMA rating. If the solution does not conform to the rating, the enclosure will not be rated to the standard and compromises the enclosure's protection.
Most thermal solutions for enclosures will have 4 different type ratings:
- NEMA Type 12: Indoor Rating
- NEMA Type 3R: Outdoor Rating
- NEMA Type 4: Outdoor Washdown Rating
- NEMA Type 4X: Washdown / Corrosion Proof Rating
A walkthrough of NEMA ratings, taken from this website here.
NEMA 12 Rating Requirements:
- Constructed (without knockouts) for indoor 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 circulating dust, lint, fibers)
- And to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing)
NEMA 3R Rating Requirements:
- 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)
- To provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow)
- And that will be undamaged by the external formation of ice on the enclosure
NEMA 4 Rating Requirements:
- 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)
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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
NEMA 4X Rating Requirements:
- 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