Enclosure Ratings

When it comes to an enclosure rating a good standard rating system needs to be utilized to define the types of environments in which certain kinds of enclosures cane be used (such as electrical). A rating system also identifies whether a fixed enclosure can stand up to certain environmental conditions. Users as well as manufacturers benefit when quality standards are in place. Overall communication, economics, and safety are improved between the seller and the buyer. Below we will be looking at the National Electrical Manufacturers Association’s (NEMA) rating scale for enclosures.

NEMA defines the standards used in North America of electrical enclosures. These enclosures are typically used in an industrial setting. Each is rated on its ability to protect against personal access to dangerous parts, and against additional areas that may be considered dangerous for an individual to physically approach. Typically a NEMA enclosure has ratings that span a wide variety of categories. These include environmental hazards such coolant, water, dust, oil, gasoline, or acetylene.

Ratings

NEMA 1

  • For general purpose reasons. Will protect against light, dust, and indirect splashing but will not completely shut out dust. This level is primarily used to prevent individuals from coming into contact with dangerous parts. It’s primarily used indoors and under normal conditions.

NEMA 2

  • This level is considered to be drip-tight. Very similar to the Type 1 but has the added benefit of drip shields. These are used when condensation may be sever (in an environment with frequent cooling or in a laundry room).

NEMA 3

  • At this level the enclosure is resistant against the weather. It provides protection against falling dirt and windblown dust. It also provides protection against the weather such as snow, sleet, rain, and does not take damage when ice forms. It can be used outdoors in multiple environments: subways, ship docks, tunnels, construction work, etc.

NEMA 3R

  • The same as 3 but it does not add protection against windblown dust.

NEMA 3S

  • The same as 3, but can operate when it’s heavily laden with ice.

NEMA 3X, 3RX, 3SX

  • The “X” indicates that the enclosure will provide additional corrosion protection. This type of enclosure is typically used near salt water.

NEMA 4 and 4X

  • This level of enclosure is considered to be water tight. It must exclude at least 65 GPM of water from a 1 in nozzle from a distance of at least 10 feet for at least 5 minutes. This type of enclosure is typically used outdoors on ship docks, wastewater treatment plants, breweries, and dairies. The “X” provides additional resistance against corrosion.

NEMA 5

  • This level of enclosure is considered to be dust tight. It comes with gaskets (or an equivalent) to keep out dust. This type of enclosure is typically used in cement plants and steel mills.

NEMA 6 and 6P

  • This level of enclosure can be submerged underwater. The design depends on the specified conditions of time and pressure. It can be submersed in water or oil. It’s primarily used in manholes, mines, and quarries. 6 can only be submersed for a short amount of time, 6P can withstand submersion for a longer period of time although neither one of them were intended to be continuously submerged.

NEMA 7

  • This level of enclosure is certified and labeled for use in areas specified for hazardous conditions. It’s designated for indoor use in Class I, groups A, B, C, and D as outlined in NFPA standard such as the NEC.

NEMA 8

  • This level of enclosure is certified and labeled for use in areas with hazardous conditions. It’s designated for indoor and outdoor use in Class I, Groups A, B, C, and D as outlined in NFPA standards such as the NFPA 70.

NEMA 9

  • This level of enclosure is certified and labeled for use in areas with hazardous conditions. It’s designated for both indoor and outdoor use in areas that are identified as Class II, Groups E, F, or G as defined in NFPA standards such as the NEC.

NEMA 10

  • This level of enclosure meets the standards of the Mine Safety and Health Administration

NEMA 11

  • This level of enclosure is considered to be general-purpose. It provides protection against the ill effects of liquids and gasses. This enclosure meets the standards of rorrosion-resistance and drip tests.

NEMA 12 and 12K

  • This level of enclosure is considered to be general-purpose. It’s intended for indoor use only, and provides protection against dropping non-corrosive liquids, falling dirt, and dust. This enclosure meets rust resistance, dust, and drip tests.

NEMA 13

  • This level of enclosure is considered to be general-purpose. It’s primarily used to protect against spraying water, dust, and non-corrosive coolants. It meets rust resistance and oil exclusion design tests.