The commonly used enclosure specification is IEC 60529, “Degrees of protection provided by enclosures (IP code),” which is referenced by a number of IEC/EN safety standards.
IEC/EN 60529 utilizes the letters "IP" ("Ingress Protection") followed by up to three digits. These three digits represent three different forms of environmental influence:
The first digit represents protection against ingress of solid objects
The second digit represents protection against ingress of liquids
The third digit represents protection against mechanical impact damage
Often, the third digit is omitted, resulting in a 2-digit IP Rating covering ingress against solid objects and liquids only. An X in place of either digit means that either the enclosure has not been tested or that the test is not applicable.
| Value | 1 - Dust Protection | 2 - Water Protection | 3 - Impact Protection |
|---|---|---|---|
| 0 | No special protection | No special protection | No special protection |
| 1 | Protected against solids upto 50mm | Protected against vertically falling drops of water | Protection against impact of 0.225 joule (e.g. 150g weight falling from 15cm height) |
| 2 | Protected against solids upto 12mm | Protected against direct sprays of water up to 15o from vertical. | Protection against impact of 0.375 joule (e.g. 250g weight falling from 15cm height) |
| 3 | Protected against solids over 2.5mm | Protected against direct sprays up to 60o from vertical | Protection against impact of 0.5 joule (e.g. 250g weight falling from 20cm height) |
| 4 | Protected against solids over 1mm | Protected against direct sprays from all directions. (limited ingress permitted) | |
| 5 | Protected against dust - limited ingress permitted (No harmful deposit) | Protected against low pressure jets from all directions (limited ingress permitted) | Protection against impact of 2.0 joule (e.g. 500g weight falling from 40cm height) |
| 6 | Dust tight | Protected against high pressure jets (limited ingress permitted) | |
| 7 | Protected against immersion between 15cm and 1m | Protection against impact of 6.0 joule (e.g. 1.5Kg weight falling from 40cm height) | |
| 8 | Protected against long periods of immersion under pressure | ||
| 9 | Protection against impact of 20.0 joule (e.g. 5Kg weight falling from 40cm height) |
In the United States, the core standard defining cabinet performance is the National Electrical Manufacturers’ Association NEMA 250, “Enclosures for Electrical Equipment (1000 Volts Maximum).” This standard is sometimes used by itself and sometimes incorporated by reference as a basis for the performance requirements of other standards (e. g., ANSI/UL 50, “Enclosures for Electrical Equipment”, or NFPA 79, “Electrical Standard for Industrial Machinery”).
The table below is courtesy of NEMA (it is part of the NEMA 250 standard). NEMA claims that the NEMA ratings in the left column are at least equivalent to the corresponding IP entries on the right, although the reverse may not be true.
| NEMA Enclosure Type Number | IP IEC Enclosure Classification Designation |
|
1 2 3 3R 3S 4 AND 4X 5 6 AND 6P 12 AND 12K 13 |
IP10 IP11 IP54 IP14 IP54 IP56 IP52 IP67 IP52 IP54 |