The purpose of this section is to provide general information on the definitions of NEMA Enclosure Types to architects, engineers, installers, and other interested parties.[For more detail and complete information, NEMA Standard Publication 250-2003, “Enclosure for Electric Equipment (1000 Volts Maximum)” should be consulted.
Non-Hazardous Locations
In Non-Hazardous Location, the specific Types, their applications, and the environmental condition they are designed to protect against, when completely and properly installed, are as follows:
Table 1: Comparison of Specific Application of Enclosures
for Indoor Nonhazardous Locations [From NEMA 250-2003]
| Provides a Degree of Protection Against the Following Conditions | Type of Enclosure | |||||||||
| 1* | 2* | 4 | 4X | 5 | 6 | 6P | 12 | 12K | 13 | |
| Access to hazardous parts | X | X | X | X | X | X | X | X | X | X |
| Ingress of solid foreign objects (falling dirt) | X | X | X | X | X | X | X | X | X | X |
| Ingress of water (Dripping and light splashing) | … | X | X | X | X | X | X | X | X | X |
| Ingress of solid foreign objects (Circulating dust, lint, fibers, and flyings**) | … | … | X | X | … | X | X | X | X | X |
| Ingress of solid foreign objects (Settling airborne, dust,lint, fibers, and flyings**) | … | … | X | X | X | X | X | X | X | X |
| Ingress of water (Hosedown and splashing water) | … | … | X | X | … | X | X | … | … | … |
| Oil and coolant | … | … | … | … | … | … | … | X | X | X |
| Oil or coolant spraying and splashing | … | … | … | … | … | … | … | … | … | X |
| Corrosive agents | … | … | … | X | … | … | X | … | … | .. |
| Ingress of water (Occasional temporary submersion) | … | … | … | … | … | X | X | … | … | … |
| Ingress of water (Occasional prolonged submersion) | … | … | … | … | … | … | X | … | … | … |
* These enclosure may be ventilated.
** These fibers and flying are nonhazardous materials and are not considered Class III type ignitable fibers or combustible flyings.
For Class III type ignitable fibers or combustible flying see the National Electrical Code, Article 500.
Table 2: Comparison of Specific Application of Enclosures
for Outdoor Nonhazardous Locations [From NEMA 250-2003]
| Provides a Degree of Protection Against the Following Conditions | Type of Enclosure | |||||||||
| 3 | 3X* | 3R | 3RX | 3S | 3SX | 4 | 4X | 6 | 6P | |
| Access to hazardous parts | X | X | X | X | X | X | X | X | X | X |
| Ingress of water (Rain, snow, and sleet **) | X | X | X | X | X | X | X | X | X | X |
| Sleet *** | … | … | … | … | X | X | … | … | … | .. |
| Ingress of solid foreign objects (Windblown dust, lint, fibers, and flyings) | X | X | … | … | … | X | X | X | X | X |
| Ingress of water (Hosedown) | … | … | … | … | … | … | X | X | X | X |
| Corrosive agents | … | X | .. | X | … | X | … | X | … | X |
| Ingress of water (Occasional temporary submersion) | … | … | … | … | … | … | … | … | X | X |
| Ingress of water (Occasional prolonged submersion) | … | … | … | … | … | … | … | … | … | X |
* These enclosure may be ventilated.
** External operating mechanisms are not required to be operable when the enclosure is ice covered.
*** External operating mechanisms are operable when the enclosure is ice covered.
Hazardous Locations
In Hazardous Location, when completely and properly installed and maintained, Type 7 and 10 enclosures are designed to contain an internal explosion without causing an external hazard. Type 8 enclosures are designed to prevent combustion through the use of oil-immersed equipment. Type 9 enclosures are designed to prevent the ignition of combustible dust.
| Type 7 | Enclosure constructed for indoor use in hazardous (classified) locations classified as Class I, Division 1, Group A, B, C, or D as defined in NFPA 70. |
| Type 8 | Enclosure constructed for either indoor or outdoor use in hazardous (classified) locations classified as Class I, Division 1, Groups A, B, C, and D as defined in NFPA 70. |
| Type 9 | Enclosures constructed for indoor use in hazardous (classified) locations classified as Class II, Division 1, Groups E, F, or G as defined in NFPA 70. |
| Type 10 | Enclosure constructed to meet the requirements of the Mine Safety and Health Administration, 30 CFR, Part 18. |
Table 3: Comparison of Specific Applications of Enclosures for Indoor Hazardous Locations
[From NEMA 250-2003]
If the installation is outdoors and/or additional protection is required by Table 1 and Table 2, a combination-type enclosure is required.
| Provides a Degree of Protection Against Atmospheres Typically Containing (See NFLPA 497M for Complete Listing) |
Enclosure Types 7 and 8, Class I Groups ** |
Enclosure Type 9,Class II Groups | |||||||
| Class | A | B | C | D | E | F | G | 10 | |
| Acetylene | I | X | … | … | … | … | … | … | … |
| Hydrogen, manufactured gas | I | … | X | … | … | … | … | … | … |
| Diethyl ether, ethylene, cyclopropane | I | … | … | X | … | … | … | … | … |
| Gasoline, hexane, butane, naphtha, propane, acetone, toluene, isoprene | I | … | … | … | X | … | … | … | … |
| Metal dust | II | … | … | … | … | X | … | … | … |
| Carbon black, coal dust, coke dust | II | … | … | … | … | … | X | … | … |
| Flour, starch, grain dust | II | … | … | … | … | … | … | X | … |
| Fibers, flyings * | III | … | … | … | … | … | … | X | … |
| Methane with or without coal dust | MSHA | … | … | … | … | … | … | … | X |
* For Class III type ignitable fibers or combustible flyings see the National Electrical Code, Article 500.
** Due to the characteristics of the gas, vapor, or dust, a product suitable for one Class or Group may not be suitable for another
Class or Group unless marked on the product.
Converting Common NEMA Enclosure Standard to IEC Enclosure Standards
IEC Publication 60529 Classification of Degrees of Protection Provided by Enclosures provides a system for specifying the enclosures of electrical equipment on the basis of the degree of protection provided by the enclosure. IEC 60529 does not specify degrees of protection against mechanical damage of equipment, risk of explosions, or conditions such as moisture (produced for example by condensation), corrosive vapors, fungus, or vermin. The NEMA Standard for Enclosures for Electrical Equipment does test for environmental conditions such as corrosion, rust , icing, oil, and coolants. For this reason, and because the test and evaluations for other characteristics are not identical, the IEC Enclosure Classification Designations cannot be exactly equated with the enclosure Type numbers in this Standard.
- NEMA and 4X is equivilent to IP66
- NEMA 12 is equivilent to IP52