Please
note that the original author that this document is based on is unknown. It is
ICEweb's intent to fully acknowledge authors. If you are the author please
contact ICEweb.
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 equipment.
Industry standards for electrical enclosures in the
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
ENCLOSURE
TYPES
Although the detailed definitions of protection afforded
by a particular enclosure type may differ slightly between the NEMA and UL
standards
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 special applications.
IEC STANDARDS
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).
AS ALWAYS --
COORDINATE
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
requirements.
Coyle is an associate and electrical group leader with
Sebesta Blomberg (
Basic conditions for various electrical enclosure types.
Type Location
1 Indoor
2 Indoor
3 Outdoor
3R Outdoor
4 Indoor/Outdoor
4X Indoor/Outdoor
6 Outdoor
12 Indoor
13 Indoor
Type Degree of Protection
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
A cross-reference of NEMA type
numbers to IP classifications.