B.3 Enclosure Ratings
NEMA and IEC
Recognition
The NEMA (National Electrical Manufacturer’s Association) enclosure
classifications are recognized in the US. The IEC Publication 529
Classifications are recognized throughout Europe and those parts of the
world that use the IEC standards as a basis for product certifications.
The following paragraphs provide a discussion of the Comparison
Between NEMA Enclosure Type Numbers and IEC Enclosure
Classification Designations.
IEC Classifications
IEC Publication 529, Classification of Degrees of Protection Provided
by Enclosures, provides a system for specifying the enclosures of
electrical equipment on the basis of the degree of protection provided by
the enclosure. IEC 529 does not specify degrees of protection against
mechanical damage of equipment, risk of explosion, or conditions such
as moisture (produced for example by condensation), corrosive vapors,
fungus, or vermin.
IEC Designations
Basically, the IEC designation consists of the letters IP followed by two
numerals. The first characteristic numeral indicates the degree of
protection provided by the enclosure with respect to persons and solid
foreign objects entering the enclosure. The second characteristic
numeral indicates the degree of protection provided by the enclosure
with respect to the harmful ingress of water.
NEMA Standards
NEMA Standards Publication 250, Enclosures for Electrical Equipment
(1000 Volts Maximum), does test for environmental conditions such as
corrosion, rust, icing, oil, and coolants. For this reason, and because the
tests and evaluations for other characteristics are not identical, the IEC
enclosure classification designations cannot be exactly equated with
NEMA enclosure type numbers.
Continued on next page
2/05 ST 3000 Release 300 Installation Guide
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