Comparing The Two Systems
NEMA and IP ratings both measure the same thing: an enclosure’s ability to withstand the ingress of dust or water. This matters because watertightness is not a binary concept: housings are not simply waterproof/not waterproof.
Varying degrees of pressure play a huge part in how well your enclosures will cope with exposure to water or dust. A splashproof enclosure will not resist prolonged immersion. And a fully submersible enclosure may not cope with high-pressure water jets.
So it’s crucial to specify the correct NEMA or IP rating for your industrial electronic enclosures. But this can be confusing because the two systems use different variables. And the numerical ratings do not correlate in the way you’d expect!
Here are some examples:
- NEMA 4 and 4X are similar to IP 66 – but NEMA 5 is similar to IP 52
- NEMA 6 and 6P are like IP 67 – but NEMA 12 and 12 K are closer to IP 52.
Yes, it is possible to compare and cross-reference ratings – but it’s crucial to specify your ingress protection requirements as accurately as possible. And for this you’ll need to examine the two rating systems in detail…
What Is The NEMA System? How Does It Work?
NEMA is the US system for measuring ingress protection. It was developed by the National Electrical Manufacturers Association, which represents around 325 electrical equipment and imaging manufacturers.
Ingress protection is judged according to 13 NEMA types, some of which include multiple classifications. This gives 21 different ratings. Importantly – a high number does not necessarily indicate a high level of watertightness: it shows the correct level of protection required for a particular application.
NEMA Ingress Protection Ratings
NEMA Types 1, 2, 5, 12 and 13 are for indoor applications. They are not recommended for outdoor use. Types 7, 8 and 9 are for hazardous environments in sectors such as mining, oil/gas and chemicals.
- 1. General-purpose. Protects against falling dust, light and indirect splashing but is not dust-tight. Used indoors and under normal atmospheric conditions. Prevents employees or objects from accidentally touching hazardous components.
- 2. Drip-tight. Similar to Type 1 but with the 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. 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 gallons of water per minute from a 1” nozzle delivered from a distance not less than 10ft for five minutes. Used outdoors on ship docks, in dairies, in wastewater treatment plants and breweries. X 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. The design depends on specified conditions of pressure and time. The enclosures can be submersible in water or oil. Used in quarries, mines, and manholes. Type 6 is temporarily submersible; 6P withstands occasional prolonged submersion. Neither is intended for continuous immersion.
- 7. Certified and labelled for use in areas with specific hazardous conditions – for indoor use in Class I, Groups A, B, C, and D environments as defined in National Fire Protection Association (NFPA) standards such as the National Electrical Code (NEC) NFPA 70.
- 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 NFPA 70.
- 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 NFPA 70.
- 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 non-corrosive liquids. These enclosures offer some protection against access to hazardous parts. They meet drip, dust and rust-resistance tests. 12K enclosures are manufactured with knockouts.
- 13. General purpose. Primarily used to provide protection against dust, spraying of water and non-corrosive coolants. Meets oil-exclusion and rust-resistance tests.
How Do IP Ratings Work?
IP ratings are the international standard for ingress protection. They are defined in IEC standard 60529 and published by the International Electrotechnical Commission. The equivalent European standard is EN 60529.