NEMA Ratings: What They Mean, and Why They Matter

You may have some new equipment or wiring to install outdoors or in an industrial facility. Experts tell you that not just any enclosure will do — it must be NEMA-rated. "NEMA rated" is an easy term to throw around. But if you're new to the game, it may leave you wondering what NEMA is, what its ratings mean and why on earth they matter so much. Come with us on a quick tour of NEMA and its ratings system — things are about to make a lot more sense.

WHAT IS NEMA?

NEMA is the National Electrical Manufacturers Association. It was formed in 1926 when the Associated Manufacturers of Electrical Supplies joined forces with the Electric Power Club. Both groups sought to create an organization that would set standards for the manufacture of safe and effective electrical products. At the time, the use of and demand for electrical devices was growing at an explosive rate. The need arose for manufacturing regulations that would not only result in safer electrical products but would also simplify the process and ensure compatibility between devices. NEMA met that need and has since continued to develop and promote standards for the constantly evolving electrical industry.

WHAT DO NEMA RATINGS HAVE TO DO WITH CABINETS AND ENCLOSURES?

While NEMA originally set out to ensure the quality of electrical devices themselves, technology and industry developed to the point where electrical components and wiring began to need protection from each environment where they were used. A simple way to provide that needed protection was to enclose vulnerable devices, controls and wires in cabinets. While NEMA isn't responsible for telecom and electrical enclosures per se, they did develop a rating system to grade and regulate them. Since then, NEMA ratings have become the go-to standards for selecting enclosures with the right features and characteristics for a particular application.

NEMA-rated enclosures are all about controlling ingress and egress, a substance's ability to either enter or exit from a given structure or space — in this case, a cabinet. While the majority of NEMA ratings are either mostly or entirely focused on blocking ingress — or the entry of a material into an enclosure — there are also several that deal with preventing egress (or the escape of a substance from the interior of an enclosure).

NEMA RATINGS AND WHAT THEY MEAN

Here's our quick, in-a-nutshell rundown of the most commonly called-for NEMA ratings — and what each one means:

• • NEMA 1: These are indoor-use enclosures that protect internal components from solid foreign objects and contaminants (like falling dirt). The NEMA 1 General Purpose Indoor enclosure also provides limited protection to personnel by restricting their access to potentially hazardous components.


• • NEMA 2: The NEMA 2 type features indoor-use enclosures that restrict worker access to hazardous components. This cabinet protects the equipment stored inside against the ingress of solid foreign contaminants and dripping or lightly splashing water.


• • NEMA 3: NEMA 3 indoor or outdoor-use cabinets limit personnel access to hazardous parts. These protect enclosed equipment from the ingress of contaminants like wind-carried dust and falling dirt, as well as moisture in the form of rain, sleet or snow. In addition, Type 3 enclosures are designed to remain undamaged even if ice forms on their outer surfaces.


• • NEMA 3R: NEMA 3R enclosures are used indoors or outdoors. These cabinets not only provide workers with a degree of protection against making contact with hazardous parts, but also defend interior components from solid contaminants, including water ingress in the form of rain, sleet or snow. The NEMA 3R weatherproof enclosures safeguard electrical equipment against ice that forms on the cabinet’s exterior.


• • NEMA 3S: 3S enclosures are used indoors or outdoors. These cabinets help to protect personnel by limiting their access to potentially harmful components. They safeguard enclosed equipment against the ingress of windborne and falling solid foreign contaminants, like dirt and dust. It keeps electrical components safe as well from water, whether in the form of rain, sleet or snow. In addition, the external mechanisms on NEMA 3S cabinets remain operable even when ice-laden.


• • NEMA 3X: Used either indoors or outdoors, these enclosures prevent the ingress of water in the form of rain, sleet or snow. NEMA 3X cabinets rebuff solid particulates like dirt and windborne dust from attaching to electrical equipment. A NEMA 3X cabinet reduces risk to personnel by limiting access to hazardous components, provides internal elements with an extra degree of protection against corrosion and isn’t damaged by the formation of ice on its exterior surfaces. This type is built with corrosion protection that provides a resistance to salt water.


• • NEMA 3SX: The NEMA 3SX cabinet is the choice in marine and industrial applications. It has all the same NEMA 3 ratings to stay guarded in the outdoors against solid objects, water ingress, airborne hazards like dust, ice formation, corrosion resistance and freezing temperatures.


• • NEMA 4: Made for indoor or outdoor use, these cabinets and enclosures help prevent worker access to hazardous components. They guard against the ingress of water in the form of rain, sleet or snow. This cabinet type is designed with gasketed doors that can clamp shut to withstand cutting coolants, pressurized liquids and water splashed or sprayed by hose. NEMA 4 enclosures prevent the entry of solid contaminants like dust and dirt. Manufacturers are required to adhere to standards that keep them undamaged, even if ice forms on their outer surfaces.


• • NEMA 4X: This type of cabinet is like its NEMA 4 counterpart, but NEMA 4X provides additional corrosion resistance. This type also guards against dust, rain, hose-directed water and ice.


• • NEMA 5: Indoor-use enclosures like NEMA 5 prevent personnel from accessing potentially dangerous components. They protect enclosed equipment from the ingress of solid foreign contaminants and objects like airborne dust, dropping dirt, lint, fibers, and fly-off particulate. These cabinets deflect dripping or lightly splashing water. NEMA 5 cabinets are often found in cement plants and steel mills, because they are designed to be extra tight to avert dust.


• • NEMA 6: These indoor or outdoor-use enclosures help prevent personnel from accessing hazardous parts, while protecting enclosed equipment against the ingress of solid foreign objects and water. These cabinets are submersible, whether exposed to hosing or temporary, limited-depth submersion. NEMA 6 cabinets are built to remain undamaged, even if ice forms on the external surface.


• • NEMA 6P: Made for indoor or outdoor use, these cabinets prevent workers from making contact with hazardous components. They help to block the entry of solid foreign matter, such as falling dirt. NEMA 6P cabinets also bar the ingress of water, whether exposed to hosing or prolonged, limited-depth submersion. NEMA 6P enclosures provide an extra measure of protection against corrosion. Manufacturers are required to build them to standards that they remain undamaged, even in the event of exterior ice formation.


• • NEMA 7: This type of indoor cabinet is constructed to be explosion-proof, even when exposed to gases and heat generating devices that are contained within NEMA 7 enclosures.


• • NEMA 8: The NEMA 8 cabinet is built with the same explosion-proof properties as NEMA 7 but can additionally resist oil immersion. It is suitable for Class II and Groups E, F or G indoor and outdoor locations.


• • NEMA 9: NEMA 9 enclosures have some of the same qualities as NEMA 8 but won’t ignite even when exposed to dust.


• • NEMA 10: The NEMA 10 cabinet is built to standards set by the Mine Safety and Health Administration, enabling it to be used to safeguard electrical components even in tunnels and where exposed to gases in mines.


• • NEMA 11: A NEMA 11 enclosure is an indoor cabinet that is corrosion-resistant versus gases and liquids. The cabinet is drip-proof, even when immersed in oil.


• • NEMA 12: Knockout-free NEMA 12 enclosures are used indoors within industrial environments. NEMA 12 cabinets have gasketed doors that keep non-pressurized water from electrical components. This type helps restrict personnel access to hazardous components, while protecting enclosed equipment from the ingress of solid foreign contaminants like airborne dust, dropping dirt, fibers, lint and fly-offs, as well as dripping and lightly splashing water.


• • NEMA 12K: The NEMA 12K indoor-use enclosures are manufactured with knockouts. This type prevents personnel contact with hazardous components. Like NEMA 12, they guard enclosed equipment from the ingress of solid foreign contaminants like dust, dirt, loose fibers, lint, fly-off particulate, and dripping or lightly-splashing water.


• • NEMA 13: NEMA 13 types are indoor-use enclosures that prevent workers from coming into contact with potentially hazardous components. This cabinet also protects enclosed equipment against the ingress of solid contaminants like dirt, dust, circulating fibers, lint, fly-off shavings and dripping or lightly splashing water. NEMA 13 enclosures additionally deflect oil and non-corrosive coolants that seep, spray, or are splashed.