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Jump to Subject:- U.S.
Electrical Enclosure Standards | Electrical
and Instrumentation Enclosure
Standards for Electrical and Instrumentation Enclosures | Electrical
and Instrumentation Enclosure Design Tips | Basic
Conditions for Various Electrical and Instrumentation Enclosure Types | Type
/ Degree of Protection for Electrical and Instrument Enclosures | Electrical
/ Instrument Enclosures - Cross Reference of NEMA Type Numbers to IP
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Be "environmentally friendly" to your
equipment's electrical components - specify the correct enclosure type.
All electrical equipment enclosures are designed to provide protection against accidental contact with the enclosed equipment and emission of sparks or flame from failure of internal components. In addition, enclosures provide varying degrees of protection against the external environment. Approval of electrical equipment enclosures for the environment is a requirement of the National Electrical Code and critical to the long-term performance of hvacr equipment.
Electrical Enclosure Standards
These standards establish basic construction requirements
as well as test methods. They define the degree of environmental protection
according to a type number common to all
Electrical and Instrumentation Enclosure Types
Although the detailed definitions of protection afforded
by a particular enclosure type may differ slightly between the NEMA and UL
Not all enclosure types are available from any given
manufacturer, so review the options offered and choose the type that meets or
exceeds the requirements of the application. A higher degree of performance
generally means higher cost, so avoid the temptation to over-specify. See http://www.iceweb.com.au/Technical/IPNEMA.htm
for details of NEMA protection definitions.
Type 2, Type 6 and Type 13 enclosures are limited to
Enclosures manufactured in
The number of different enclosure classifications possible
(48) under the IEC standard is much greater than the number under the NEMA and
UL standards. IEC standards tend to allow more application-specific designs,
while U.S. standards cover a broad range of applications with a fewer number of
ratings. One manufacturer offers a cross-reference of NEMA Type numbers to IP
classifications (Table 2).
Coordinate the enclosure types you specify for equipment
with the electrical designer. Chances are, they are placing electrical equipment
in the same spaces as other equipment and have addressed the enclosure
requirements. Many electrical construction specifications include a general
section defining area classifications and enclosure types that you can reference
in your specifications.
None of the above information applies to locations where
flammable or explosive liquids, gases, fibers, or dusts are present. Enclosures
for these areas must comply with more stringent requirements and be approved for
the type and ignition characteristics of the hazardous substance. Seek direction
from an electrical engineer qualified in hazardous location design for equipment
1 Accidental contact only - No environmental protection
2 Falling water or dirt
3 Dust, rain, sleet, ice
3R Rain, sleet, ice
4 Dust, dripping, falling and hose-directed water
4X Dust, dripping, falling and hose-directed water, corrosion
6 Submersible (occasional and temporary, limited depth)
12 Dust, dripping and falling non-corrosive liquids
13 Dust, dripping, falling and spraying non-corrosive liquids
1 IP 23
2 IP 30
3 IP 64
3R IP 32
4 IP 66
4X IP 66
6 IP 67
12 IP 55
13 IP 65