As a way of standardizing enclosure
performance, organizations like NEMA (National Electrical Manufacturers
Association), UL (Underwriters Laboratories),
CSA (Canadian Standards
Association), IEC (International Electrotechnical Commission), VDE
(Institute of German Electronics Engineers), and TÜV Rheinland of North
America use rating systems to identify an enclosure’s ability to resist
external environmental influences. Resistance to everything from dripping
liquid, to hose-down, to total submersion is defined by the rating
systems. These ratings are intended to provide more informed choices and
ultimately a safer work area. However, there are differences among them.
|
Enclosure
Rating Descriptions
|
| NEMA,
UL, & CSA type rating |
Approximate
IEC/IP classification |
Abbreviated
protection description |
| 1 |
IP23 |
Indoor
protection from contact with contents. |
| 2 |
IP30 |
Indoor
with limited protection from dirt & water. |
| 3 |
IP64 |
Outdoor
with some protection from rain, sleet, windblown dust, and ice
damage. |
| 3R |
IP32 |
Outdoor
with some protection from rain, sleet, and ice damage. |
| 4 |
IP66 |
Indoor
and outdoor with some protection from windblown dust, rain,
splashing water, hose-directed water, and ice damage. |
| 4X |
IP66 |
Indoor
and outdoor with some protection from corrosion, windblown dust,
rain, splashing water, hose-directed water, and ice damage. |
| 6 |
IP67 |
Indoor
and outdoor with protection from hose-directed water, entry of
water during submersion at limited depth, ice damage. |
| 12 |
IP55 |
Indoor
with protection from dust, falling dirt, and dripping
non-corrosive liquids. |
| 13 |
IP65 |
Indoor
with protection against dust, spraying water, oil, and
non-corrosive liquids. |
Source:
Control Engineering
Click for a Complete listing of NEMA,
UL, CSA, and IEC
standards and ratings |
In North America NEMA,
UL, and CSA
are the commonly recognized organizations. Their ratings are based on
similar application descriptions and expected performance. UL and CSA both
require enclosure testing by qualified evaluator labs. They also send site
inspectors to ensure manufacturers adhere to prescribed methods and
material specifications. NEMA does not require independent testing and
leaves compliance up to the manufacturer.
North American enclosure rating
systems also include a 4X rating that indicates resistance to corrosion.
This rating is based on the enclosure’s ability to withstand prolonged
exposure to saltwater spray.
A 4X rating is a good indicator that
an enclosure can resist corrosion; it does not provide information on how
a specific corrosive agent will affect a given enclosure material. It is
best to analyze the specific application and environment to determine the
best enclosure choice.
European ratings In Europe, IEC
ratings are based on performance criteria similar to NEMA, with different
interpretations of enclosure performance. For example, UL and
CSA test
requirements specify failure of the watertight test if a single drop of
water enters the enclosure. IEC’s standards for each ingress protection
(IP) level specifies the amount of water allowed entering the enclosure.
IEC does not specify degrees of
protection against risk of explosions or conditions such as moisture or
corrosive vapors; NEMA does. Because of this reason and because tests and
evaluations for other characteristics are not identical, IEC enclosure
classification designations cannot be exactly equated with NEMA enclosure
type numbers.
IEC uses IP ratings to define the
degree of protection provided by an enclosure using a two-digit numerical
classification. The first number defines the degree of protection against
solid objects; and the second number defines the degree of protection
against water.
To promote free trade movement to
and from the European Union (EU), directives are being harmonized for
health, safety, environment, and consumer protection using the CE
(Conformité Européenne) Mark.
For industrial control systems, the
CE Mark appears only on enclosures containing all active control system
components. Responsibility of ensuring compliance to applicable EU
directives and harmonized standards belongs with the final equipment
manufacturer. |
