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| Definition of NEMA Ratings |
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| What does NEMA 4 rated mean?
In non-hazardous locations, there are several
different NEMA ratings for specific enclosure "types",
their applications, and the environmental conditions
they are designed to protect against, when completely
and properly installed. The following provides an
overview of the NEMA Types. For complete definitions,
descriptions, and test criteria, see the National
Electrical Manufacturers Association (NEMA) Standards
Publication No. 250.
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NEMA 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.
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NEMA 2
Same as NEMA 1 including protection
against dripping and light splashing of liquids.
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NEMA 3
Enclosures constructed for either
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 the external
formation of ice on the enclosure.
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NEMA 3R
Same as NEMA 3 excluding protection
against windblown dust.
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NEMA 3S
Enclosures constructed for either
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 in which the external mechanism (s) remain
operable when ice laden.
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NEMA 4
Enclosures constructed for either
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 the external formation of ice on the
enclosure.
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NEMA 4X
Same as NEMA 4 including protection
against corrosion.
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NEMA 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 to
provide a degree of protection against dripping and
light splashing of liquids.
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NEMA 6
Enclosures constructed for either
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 the external formation of ice on the
enclosure.
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NEMA 6P
Same as NEMA 6 including protection
against the entry of water during prolonged submersion
at a limited depth.
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NEMA 7
Enclosures are for indoor use in
locations classified as Class I, Groups A, B, C, or D
and shall be capable of withstanding the pressures
resulting from an internal explosion of specified gases,
and contain such an explosion sufficiently that an
explosive gas-air mixture existing in the atmosphere
surrounding the enclosure will not be ignited. Enclosed
heat generating devices shall not cause external
surfaces to reach temperatures capable of igniting
explosive gas-air mixtures in the surrounding
atmosphere. Enclosures shall meet explosion,
hydro-static, and temperature design tests.
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NEMA 9
Enclosures are intended for indoor
use in locations classified as Class II, Groups E, F, or
G, and shall be capable of preventing the entrance of
dust. Enclosed heat generating devices shall not cause
external surfaces to reach temperatures capable of
igniting or discoloring dust on the enclosure or
igniting dust-air mixtures in the surrounding
atmosphere. Enclosures shall meet dust penetration and
temperature design tests, and aging of gaskets (if
used).
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NEMA 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 against dripping and light
splashing of liquids.
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NEMA 12K
Same as NEMA 12 including
enclosures constructed with knockouts.
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NEMA 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 against the
spraying, splashing, and seepage of water, oil, and
non-corrosive coolants. |
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