Industry standards for computer enclosures exist to promote safety, encourage design efficiency, and define minimum levels of product performance.
If industry standards were not set in place, there would be wide variations in enclosure performance and price. More times than not, end users and system integrators do not clearly understand the difference between the standards, which leads to suppliers unable to provide products that meet necessary and vital requirements. When customers tend to focus solely on the lowest price for a product, the decision could ultimately lead to high maintenance expenses, component failures, replacement costs, and safety issues. All of this will just end up costing more money in the long run. Finding a computer enclosure that will withstand various harsh situations will actually save money, because the enclosure will last for many, many years.
NEMA (National Electrical Manufacturer’s Association) and UL (Underwriters Laboratory) are two of the most commonly and globally recognized standards organizations. NEMA develops standards and specifications detailing minimum enclosure construction, performance and test criteria and corrosion resistance. On the other hand, UL is an independent product safety certification organization that actually tests individual products to assure that they will last. As the UL Standards website states, “UL Standards are used to assess products; test components, materials, systems and performance; and evaluate environmentally sustainable products, renewable energies, food and water products, recycling systems and other innovative technologies.”
So, what is the difference?
NEMA vs. UL
NEMA simply indicates the computer enclosure design intent and does not mandate compliance via a third party testing or on-site compliance visit. The American National Standards Institute describes NEMA as the following: “the National Electrical Manufacturers Association, is a nonprofit organization that develops and publishes over 500 standards regarding the production and manufacturing processes for technologies involving the generation, transmission and use of electricity.” A computer enclosure can be built to meet NEMA standards, but actual performance compliance is at the discretion of the enclosure manufacturer. UL certification is a formal confirmation that the required enclosure construction and performance are met after a series of testing has been completed.
Defining NEMA Ratings (defined by UL 50, 50E and NEMA250)
When discussing enclosure standard types, two main categories exist: indoor and indoor/outdoor. The indoor NEMA ratings are Type 1, Type 2, Type 5, Type 12, and Type 13. For example, Type 1 will protect against hazardous pieces that might fall or hit the enclosure and falling dirt, but has no protection against any liquids. Type 13 will protect against dirt, dust, lint, fibers, flying objects, plus dripping or splashing fluids and oil and non-corrosive coolants. On the other hand, indoor and outdoor enclosure types are Type 3, Type 3R, Type 4, Type 4X, Type 6 and Type 6P. The indoor/outdoor types can protect against a variety of natural or man-made occurrences, such as snow, rain, sleet, hose-directed fluids, and Type 6P will even protect against submersion. Most of the indoor/outdoor types will also protect against dirt, dust and solid foreign objects. Not sure what is protected? Review the chart below.
Before deciding on which enclosure will work for the job, it is best to review the entire NEMA chart and make sure that the enclosure type will withstand whatever is thrown or splashed at it.
NEMA RATING CHART
NEMA Rating (indoor)
Definition
1
Enclosures constructed for indoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment and to provide a degree of protection against falling dirt
2
Enclosures constructed for indoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, and to provide a degree of protection against dripping and light splashing of liquids
5
Enclosures constructed for indoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against settling airborne dust, lint, fibers and flyings: and to provide a degree of protection against dripping and light splashing of liquids
12
Enclosures constructed (without knockouts) for indoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against circulating dust, lint, fibers and flyings: and to provide a degree of protection to against dripping and light splashing of liquids
13
Enclosures constructed for indoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against circulating dust, lint, fibers and flyings: and against the spraying, splashing and seepage of water, oil and non-corrosive coolants.
NEMA Rating (indoor/outdoor)
Definition
3
Enclosures constructed for indoor or outdoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow and windblown dust; and that will be undamaged by external formation of ice on the enclosure
3R
Enclosures constructed for indoor or outdoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet and snow; and that will be undamaged by external formation of ice on the enclosure
4
Enclosures constructed for indoor or outdoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water and hose-directed water; and that will be undamaged by external formation of ice on the enclosure
4X
Enclosures constructed for indoor or outdoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water and hose-directed water, and corrosion; and that will be undamaged by external formation of ice on the enclosure
6
Enclosures constructed for indoor or outdoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against hose-directed water and the entry of water during occasional temporary submersion at a limited depth; and that will be undamaged by external formation of ice on the enclosure
6P
Enclosures constructed for indoor or outdoor use; to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against hose-directed water and the entry of water during occasional prolonged submersion at a limited depth; and that will be undamaged by external formation of ice on the enclosure
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