Understanding Environmental Rating Standards

 

National Electrical Manufacturers Association (NEMA)

NEMA 1
General purpose. For indoor protection where conditions are not unusually severe.
NEMA 2
Drip-tight. For indoor use. Designed to exclude falling moisture or dirt. Particularly applicable to cooling rooms, laundries, etc., where condensation is prevalent.
NEMA 3
Weatherproof. For outdoor use. Designed to withstand all normal exposure to natural elements. Controls mounted on pullout racks for easy access. With rain hood and weather seals.
NEMA 4
Watertight and dust-tight. Intended for use indoors or outdoors to protect equipment against splashing, falling, or hose-directed water, external condensation, and water seepage. Withstands water pressure from 1" hose nozzle, 65 gallons per minute, from distances of not less than 10 feet for a period of five minutes.
NEMA 4X
Watertight, dust-tight, and corrosion-resistant enclosures. Meets the same qualifications as NEMA 4 but with added corrosion resistance.
NEMA 5
Dust-tight. Equipped with dust-tight gaskets. Suitable for mills and other high-dust atmospheres.
NEMA 6
Submersible. For submerged operation under specified pressures and time.
NEMA 7
Enclosures for indoor Class I, Division 1 hazardous locations with gas or vapor atmospheres. National Electrical Code class 1 (circuit breaks in air).
NEMA 8
Hazardous locations. National Electrical Code class 1 (circuit breaks immersed in oil).
NEMA 9
For indoor Class II, Division I hazardous locations with combustible dust atmospheres. National Electrical Code class 2.
NEMA 10
Explosion-proof. Meets U.S. Bureau of Mines requirements for explosive atmospheres. Units that are designed to contain gas or vapor explosions within the enclosure and prevent ignition of the surrounding atmospheres.
NEMA 11
Acid- or fume-resistant. Provides for immersion of enclosed equipment in oil.
NEMA 12
Industrial use. Excludes oils, dust, moisture, to satisfy individual requirements.
NEMA 13
Oil-tight and dust-tight. Intended for indoor use.

International Electrotechnical Commission (IEC)

IEC standards use a designation of IP(ab) where (a) denotes the enclosure's degree of protection against contact and ingress of solid bodies and (b) denotes the enclosure's degree of protection against ingress of water.

(a) Solids Protection

0  No special protection.

1  Protection against ingress of solid objects with a diameter greater than 50mm.

2  Protection against penetration by solid objects with a diameter greater than 12mm.

3  Protection against ingress of solid objects with a diameter greater than 2.5mm.

4  Protection against ingress of solid objects with a diameter greater than 1mm.

5  Dust-protected.

6  Dust-tight.

(b) Water Protection

0  No special protection.

1  Protection against dripping water falling vertically.

2  Protection against dripping water falling at 75° to 90° angles.

3  Protection against water being sprayed.

4  Protection against water being splashed.

5  Protection against water jets.

6  Protection against heavy seas.

7  Protection against the effects of immersion.

8  Protection against indefinite immersion.

Comparing IEC to NEMA Ratings — Rough Equivalents

Enclosure IP21 IP30 IP32 IP64 IP65 IP66 IP67
NEMA 1 Check            
NEMA 2   Check          
NEMA 3R     Check        
NEMA 3, 3S       Check      
NEMA 4, 4X           Check  
NEMA 6             Check
NEMA 12, 13         Check