Industry Definitions

NEMA Standards

An enclosure is a surrounding case constructed to provide a degree of protection to personnel against incidental contact with the enclosed equipment and to provide a degree of protection to the enclosed equipment against specified environmental conditions. NEMA 250-2003.

General Definitions Pertaining To Enclosures

Cover: An unhinged portion of an enclosure that covers an opening.

Degree of Protection: The extent of protection provided by an enclosure against access to hazardous parts, against ingress of foreign solid objects and/or against ingress of water and verified by standardized test methods.

Design Tests: Tests to demonstrate performance of a product designed to applicable standards. (Note: Design tests are not intended to be production tests.) NEMA 250-2003.

Door: A hinged portion of an enclosure that covers an opening. NEMA 250-2003.

Hazardous (Classified) Locations are those areas, which may contain hazardous (classified) materials in sufficient quantity to create an explosion. See Article 500 of the National Electrical Code. NEMA 250-2003.

Hazardous (Classified) Materials are those gases, vapors, combustible dusts, fibers, or flyings, which are explosive under certain conditions. NEMA 250-2003.

Hazardous Parts are parts that are hazardous to approach or touch.

Indoor Locations are those areas, which are protected from exposure to the weather. NEMA 250-2003.

Knockout is a portion of the wall of an enclosure so fashioned that it may be removed readily by a hammer, screwdriver, and pliers at the time of installation in order to provide a hole for the attachment of an auxiliary device or raceway, cable, or fitting. NEMA 250-2003.

Non-Hazardous Locations: Areas, which do not contain hazardous (classified) materials in sufficient quantity to create an explosion. NEMA 250-2003.

Non-Ventilated means constructed so as to provide no intentional circulation of external air through the enclosure. NEMA 250-2003.

Oil-Resistant Gaskets are those made of material, which is resistant to oil, or oil fumes. NEMA 250-2003.

Outdoor Locations are those areas, which are exposed to the weather. NEMA 250-2003.

Ventilated means constructed so as to provide for the circulation of external air through the enclosure to remove excess heat, fumes, or vapors. NEMA 250-2003.

Definitions Pertaining to Non-Hazardous Locations

Type 1 Enclosures are constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts and to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt)

Type 2 Enclosures are constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirty, and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing).

Type 3 Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt) and windblown dusty, to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow), and that will be undamaged by the external formation of ice on the enclosure.

Type 3R Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt) to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow), and that will be undamaged by the external formation of ice on the enclosure.

Type 3S Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust) to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow), red for which the external mechanisms) remain operable when ice laden.

Type 3X Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt) and windblown dusty, to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow), that provides an additional level of protection against corrosion and that will be undamaged by the external formation of ice on the enclosure.

Type 3XR Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt), to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow), that will be undamaged by the external formation of ice on the enclosure that provides an additional level of protection against corrosion, and that will be undamaged by the external formation of ice on the enclosure.

Type 3SX Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dusty, to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snowy, that provides an additional level of protection against corrosion, and for which the external mechanisms) remain operable when ice laden.

Type 4 Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dusty, to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water), and that will be undamaged by the external formation of ice on the enclosure.

Type 4X Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (windblown dusty, to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water), that provides an additional level of protection against corrosion, and that will be undamaged by the external formation of ice on the enclosure.

Type 5 Enclosures are constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and settling airborne dust, lint, fibers, and flyings), and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing).

Type 6 Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt), to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (hose directed water and the entry of water during occasional temporary submersion at a limited depths), and that will be undamaged by the external formation of ice on the enclosure.

Type 6P Enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt), to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (hose directed water and the entry of water during prolonged submersion at a limited depths), that provides an additional level of protection against corrosion and that will be undamaged by the external formation of ice on the enclosure.

Type 12 Enclosures are constructed (without knockouts) for indoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and circulating dust, lint, fibers, and flyings), and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing).

Type 12K Enclosures are constructed (with knockouts) for indoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (failing dirt and circulating dust, lint, fibers, and flyings), and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing).

Type 13 Enclosures are constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and circulating dust, lint, fibers, and flyings), to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing), and to provide a degree of protection against the spraying, splashing, and seepage of oil and non-corrosive coolants.

Definitions Pertaining to Hazardous (Classified) Locations

Type 7 Enclosures constructed for indoor use in hazardous locations classified as Class I, Division 1, Groups A, B, C, or D, as defined in NFPA70. NEMA 250-2003.

Type 8 Enclosures constructed for either indoor or outdoor use in hazardous locations classified as Class I, Division 1, Groups A, B, C, or D, as defined in NFPA70. NEMA 250-2003.

Type 9 Enclosures constructed for indoor use in hazardous locations classified as Class II, Division 1,Groups E, F, or G, as defined in NFPA70. NEMA 250-2003.

Type 10 Enclosures constructed to meet the requirements of the Mine Safety and Health Administration, 30 CFR, Part 18. NEMA 250-2003. NEMA 250-2003.

Application for Enclosure Types

Type 1 general-purpose enclosures are suitable for general-purpose application indoors, where atmospheric conditions are normal. These enclosures serve as protection against falling dirt but are not dust tight.

Type 2 drip-tight (indoor) enclosures are similar to Type 1 enclosures, suitable for application where condensation may be severe, such as that encountered in cooling rooms or laundries.

Type 3 enclosures provide proper protection against windblown dust and weather hazards such as dirt, rain, sleet, or snow. They are suitable for application outdoors on ship docks, canal locks, construction work, and for application in subways and tunnels, use indoors where dripping water is a problem.

Type 3R enclosures provide proper protection falling dirt, rain, sleet, snow, undamaged by external formation of ice. They are suitable for application outdoors, they will not withstand wind blown dust.

Type 4 watertight enclosures are suitable for dairies, breweries, etc., where the enclosure may be subjected to large amounts of water from any angle. (They are not submersible).

Type 4X corrosion resistant enclosures satisfy the same requirements of Type 4, in addition, they are suitable for food processing plants, dairies, refineries, and other industries where corrosion is prominent.

Type 6 submersible enclosures are suitable for application where the equipment may be subject to occasional temporary submersion, such as quarries, mines, and manholes. The enclosure design will depend upon the specified conditions of pressure and time.

Type 9 hazardous location enclosures—Class II, Group E, F, or G. These enclosures are designed to meet the requirements of the “Canadian Electrical Code” Part I for Class II hazardous locations, and CSA codes section 18, Class II, Group E, F, and G.

  • Class II, Group E - atmospheres containing metal dust
  • Class II, Group F - atmospheres containing carbon black, coal, or coke dust
  • Class II, Group G - atmospheres containing flour, starch, or grain dust

Type 12 industrial use enclosures protect against dripping and light splashing of liquids. Hammond Type 12 enclosures meet JIC standard and also satisfy requirements of NEMA.

Type 12K industrial use enclosure same as type 12 but includes knockouts in the top and bottom end walls only.

Type 13 industrial use enclosures, protection against dust, spraying of water, oil, and non-corrosive coolant. These enclosures are suitable for application to machine tools and other industrial processing machines.

Comparison of Specific Applications of Enclosures for Indoor Non Hazardous Locations

Provides a Degree of Protection Against Enclosure Type
The Following Environment Conditions 4 4X 12 13
Incidental contact with enclosed equipment
Falling dirt
Falling liquids and lightly splashing  
Circulating dust, lint and fiber flyings²  
Settling airborne dust, lint and fiber flyings²  
Hosedown and splashing water      
Oil and coolant seepage      
Oil and coolant spraying and splashing        
Corrosive agents        

¹ These enclosures may be ventilated
² These fibers and flyings are nonhazardous materials and are not considered Class III type ignitable fibers or combustible flyings. For Class III type ignitable fibers or combustible flyings see the National Electrical Code, article 500.

Comparison of Specific Applications of Enclosures for Outdoor Non Hazardous Locations

Provides a Degree of Protection Against  Enclosure Type
The Following Environment Conditions 3R¹ 4 4X
Incidental contact with enclosed equipment
Rain, snow, and sleet ²
Windblown dust, lint and fiber flyings  
Hosedown  
Corrosive agents    

¹ These enclosures may be ventilated
² External operating mechanisms are not required to be operable when the enclosure is ice covered.