Published on: May 25, 2016 by Blair Haas
There is often confusion about the various rating systems for the protection of equipment within an enclosure. We are often asked which system is best and how are they different? If the customer is in the US, are they better off buying NEMA boxes or one with an IP rating, or does it even matter? While there are no hard and fast answers to the question of which is best, we thought it might be helpful to provide a few details to help the customer navigate these systems.
NEMA Box in the Bud PIP series
IP, or ingress protection marking, is the International standard, typically used throughout the world and only recently gaining adherents in the US. It is based on the IEC (International Electrotechnical Commission) standard 60529. NEMA ratings were established by the National Electrical Manufacturers Association and take a somewhat different approach to designating protection levels than does the IP system. While there can be self-testing (and these are typically noted by phrases such as “designed to meet IPXX”), there are regulatory agencies such as UL for NEMA and TUV for IP that will perform and certify the tests for the various levels of protection. While there are charts that purport to show the relationship between and IP rating and a NEMA rating, the differences can be subtle yet important.
An IP ratings typically is a two digit number. The first digit stands for the level of solid particle protection while the second digit represents the level of liquid ingress protection. The levels for the solid particles range from 0 for no protection to 6 which is dust tight. The second digit ranges from 0 (no protection) to 9.
The NEMA system uses one number to represent the level of protection although confusingly the higher the number does not necessarily represent increased security but rather different types of water resistance.
The other difference is that the tests performed to certify the ratings might be quite different although they produce a similar level of protection. For example, the spray test on a NEMA 4 box is 65 GPM of water from a 1 inch nozzle delivered from at least 10 feet away for 5 minutes. Some may suggest that NEMA 4 is the same as IP66, but the IP66 test is for 3 minutes instead of 5, 3 meters instead of 10 feet and with a slightly different sized nozzle. Although close, they are not the identical.
Below are the charts with a brief explanation of the protection levels and testing process. used to rate IP Boxes and NEMA Boxes. As always, if you have any questions, never hesitate to contact the enclosure manufacturer for exact details and certifications.
| First Number | ||
| Solids Protection | ||
| Level | Object size protected against | Effective against |
| 0 | — | No protection against contact and ingress of objects |
| 1 | >50 mm | Any large surface of the body, such as the back of a hand, but no protection against deliberate contact with a body part |
| 2 | >12.5 mm | Fingers or similar objects |
| 3 | >2.5 mm | Tools, thick wires, etc. |
| 4 | >1 mm | Most wires, slender screws, ants etc. |
| 5 | Dust protected | Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment. |
| 6 | Dust tight | No ingress of dust; complete protection against contact (dust tight). A vacuum must be applied. Test duration of up to 8 hours based on air flow |
| Second Number | |||
| Liquid Protection | |||
| Level | Protected against | Effective against | Details |
| 0 | Not protected | — | — |
| 1 | Dripping water | Dripping water (vertically falling drops) shall have no harmful effect. | Test duration: 10 minutes |
| Water equivalent to 1 mm rainfall per minute | |||
| 2 | Dripping water when tilted up to 15° | Vertically dripping water shall have no harmful effect when the enclosure is tilted at an angle up to 15° from its normal position. | Test duration: 10 minutes |
| Water equivalent to 3 mm rainfall per minute | |||
| 3 | Spraying water | Water falling as a spray at any angle up to 60° from the vertical shall have no harmful effect. | Test duration: 5 minutes |
| Water volume: 0.7 litres per minute | |||
| Pressure: 50–150 kPa | |||
| 4 | Splashing of water | Water splashing against the enclosure from any direction shall have no harmful effect. | Test duration: 5 minutes |
| Water volume: 10 litres per minute | |||
| Pressure: 50–150 kPa | |||
| 5 | Water jets | Water projected by a nozzle (6.3 mm) against enclosure from any direction shall have no harmful effects. | Test duration: at least 3 minutes |
| Water volume: 12.5 litres per minute | |||
| Pressure: 30 kPa at distance of 3 m | |||
| 6 | Powerful water jets | Water projected in powerful jets (12.5 mm nozzle) against the enclosure from any direction shall have no harmful effects. | Test duration: at least 3 minutes |
| Water volume: 100 litres per minute | |||
| Pressure: 100 kPa at distance of 3 m | |||
| 6K | Powerful water jets with increased pressure | Water projected in powerful jets (6.3 mm nozzle) against the enclosure from any direction, under elevated pressure, shall have no harmful effects. | Test duration: at least 3 minutes |
| Water volume: 75 litres per minute | |||
| Pressure: 1000 kPa at distance of 3 m | |||
| 7 | Immersion up to 1 m | Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 m of submersion). | Test duration: 30 minutes |
| Tested with the lowest point of the enclosure 1000 mm below the surface of the water, or the highest point 150 mm below the surface, whichever is deeper. | |||
| 8 | Immersion 1 m or more | The equipment is suitable for continuous immersion in water under conditions which shall be specified by the manufacturer. However, with certain types of equipment, it can mean that water can enter but only in such a manner that it produces no harmful effects. The test depth and/or duration is expected to be greater than the requirements for IPx7. | Test duration: continuous immersion in water |
| Depth specified by manufacturer, generally up to 3 m | |||
| 9K | Powerful high temperature water jets | Protected against close-range high pressure, high temperature spray downs. | Test duration: 30 seconds in each of 4 angles (2 minutes total) |
| Smaller specimens rotate slowly on a turntable, larger specimens are tested freehand for a longer time. Smaller specimens are tested from 4 specific angles. | Water volume: 14–16 litres per minute | ||
| There are specific requirements for the nozzle used for the testing. | Water temperature: 80 °C | ||
| NEMA Type | Definition |
| 1 | General-purpose. Protects against dust, light, and indirect splashing but is not dust-tight; primarily prevents contact with live parts; used indoors and under normal atmospheric conditions. |
| 2 | Drip-tight. Similar to Type 1 but with addition of drip shields; used where condensation may be severe (as in cooling and laundry rooms). |
| 3 | Weather-resistant. Protects against falling dirt and windblown dust, against weather hazards such as rain, sleet and snow, and is undamaged by the formation of ice. Used outdoors on ship docks, in construction work, and in tunnels and subways. |
| 3R | As 3, but omits protection against windblown dust. |
| 3S | As 3, but also operable when laden with ice. |
| 3X, 3RX, 3SX | X indicates additional corrosion protection; commonly used near salt water. |
| 4 and 4X | Watertight. Must exclude at least 65 GPM of water from 1-in. nozzle delivered from a distance not less than 10 ft for 5 min. Used outdoors on ship docks, in dairies, and in breweries. X (as 4X) indicates additional corrosion resistance. |
| 5 | Dust-tight. Provided with gaskets or equivalent to exclude dust; used in steel mills and cement plants. |
| 6 and 6P | Submersible. Design depends on specified conditions of pressure and time; submersible in water or oil; used in quarries, mines, and manholes. 6 is temporarily submersible, 6P withstands occasional prolonged submersion. Neither are intended for continuous submersion. |
| 7 | Certified and labeled for use in areas with specific hazardous conditions: for indoor use in Class I, Groups A, B, C, and D environments as defined in NFPA standards such as the NEC. |
| 8 | Certified and labeled for use in areas with specific hazardous conditions: for indoor and outdoor use in locations classified as Class I, Groups A, B, C, and D as defined in NFPA standards such as the NEC. |
| 9 | Certified and labeled for use in areas with specific hazardous conditions: for indoor and outdoor use in locations classified as Class II, Groups E, F, or G as defined in NFPA standards such as the NEC. |
| 10 | MSHA. Meets the requirements of the Mine Safety and Health Administration, 30 CFR Part 18 (1978). |
| 11 | General-purpose. Protects against the corrosive effects of liquids and gases. Meets drip and corrosion-resistance tests. |
| 12 and 12K | General-purpose. Intended for indoor use, provides some protection against dust, falling dirt, and dripping noncorrosive liquids. Meets drip, dust, and rust resistance tests. |
| 13 | General-purpose. Primarily used to provide protection against dust, spraying of water and noncorrosive coolants. Meets oil exclusion and rust resistance design tests. |
