Electrical equipment performs several important functions in modern built environments. The enclosures that house this equipment must provide adequate protection, considering the local conditions. Enclosures built to National Electrical Manufacturers Association standards are NEMA rated, while those built to IEC standards are IP (International Protection) rated.
As increased protection comes at a higher cost, very complicated enclosures are not recommended. For example, there is no reason to use watertight and corrosion-proof enclosures in commercial offices, but they become necessary in marine environments.
This article describes the main types of enclosures in both the NEMA and IP rating systems. Please note that this is an informational guide, not intended to be used in place of NEMA and IEC standards in real-world applications.
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NEMA Enclosures Overview
NEMA enclosure types are specified using numbers, alone or in combination with letters. Each type has different protection features and a higher number does not always mean more protection. NEMA enclosures range from types 1 through 13, where types 7 through 10 indicate enclosures suitable for hazardous locations (designed to prevent ignition of flammable solids, liquids, and vapors).
NEMA Enclosures for Non-Hazardous Locations
|
NEMA CLASSIFICATION |
DESCRIPTION |
|
Type 1 |
Designed for indoor use only. |
|
Type 2 |
Designed for indoor use only |
|
Type 3 |
Designed for indoor and outdoor use. |
|
Type 3R |
Similar to Type 3, but solid protection is against falling dirt only. |
|
Type 3S |
Same as Type 3, with an additional feature: the opening mechanism works when covered in ice. |
|
Types 3X, 3RX and 3SX |
Same protection as types 3, 3R and 3S, in addition to corrosion resistance. |
|
Type 4 |
Designed for indoor and outdoor use. |
|
Type 4X |
Same protection as Type 4, more corrosion resistance. |
|
Type 5 |
Designed for indoor use only. |
|
Type 6 |
Designed for indoor and outdoor use. |
|
Type 6P |
Same protection as Type 6, more resistance to corrosion and prolonged immersion (even at low depths). |
|
Type 11 |
Designed for indoor use only. |
|
Type 12 |
Designed for indoor use only. |
|
Enter 12K |
Same protection as Type 12K, but includes pre-drilled holes. |
|
Type 13 |
Designed for indoor use only. |
NEMA Enclosures for Hazardous Locations
Hazardous location enclosures are designed to prevent explosions. This is achieved by isolating ignition sources from flammable substances or by designing enclosures to withstand an internal explosion without breaking.
|
NEMA CLASSIFICATION |
DESCRIPTION |
|
Type 7 |
Designed for indoor use only. |
|
Type 8 |
Designed for indoor and outdoor use. |
|
Type 9 |
Designed for indoor use only. |
|
Type 10 |
Built in accordance with Mine Safety and Health Administration requirements. |
IP Enclosures Overview
IP enclosures also indicate their protection rating with numbers, but the logic is simpler than with NEMA enclosures:
- The first digit indicates solid protection, while the second indicates liquid protection.
- In each of the digits, a higher number indicates greater protection, a principle that does not always apply to NEMA enclosures.
The first digit goes from 0 to 6, while the second goes from 0 to 8 (plus a special classification indicated as 9k). This means that IP00 is the lowest protection rating, while IP69k is the highest. IP ratings are summarized in the tables below.
Solid Protection
|
1ST DIGIT |
DESCRIPTION |
|
0 |
No protection. |
|
1 |
Particles larger than 50 mm. |
|
two |
Particles larger than 12.5 mm. |
|
3 |
Particles larger than 2.5 mm. |
|
4 |
Particles larger than 1.0 mm. |
|
5 |
Limited dust ingress. |
|
6 |
Completely dustproof. |
Liquid Protection
|
2ND DIGIT |
DESCRIPTION |
|
0 |
No protection. |
|
1 |
Vertical water dripping. |
|
two |
Vertical water drip, cabinet tilted 15°. |
|
3 |
Water spraying up to 60° from the vertical axis. |
|
4 |
Spraying water from any direction. |
|
5 |
6.3mm nozzle water jet. |
|
6 |
Powerful water jet with 12.5 mm nozzle. |
|
7 |
Temporary immersion up to 1 m. |
|
8 |
Prolonged immersion at depths greater than 1 m. |
|
9k |
Short-range, high-temperature, high-pressure water jets. |
Conclusion
Cabinet selection is a very important aspect of electrical design. If the enclosure does not provide adequate protection for the application at hand, the electrical components will likely fail soon. On the other hand, overspecified cabinets represent wasted capital that could be dedicated to other design features or energy efficiency measures.
When dealing with the NEMA and IP rating systems, consider that neither is better than the other; they simply differ in the standards followed and the way protection is specified. However, consider that NEMA standards are dominant in North America.
