Outdoor Cabinets

NEMA Ratings: What They Mean, and Why They Matter

So, you have some new equipment or wiring to install outdoors or in an industrial facility, and they tell you that not just any enclosure will do: it has to 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 actually the National Electrical Manufacturers Association, which was formed in 1926 when the Associated Manufacturers of Electrical Supplies joined forces with the Electric Power Club 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, and the need arose for manufacturing regulations that would not only result in safer electrical products, but also simplify the process and ensure compatibility between devices. NEMA met that need, and has continued to develop and promote standards for the constantly-evolving electrical industry ever since.

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 the environments that they were used in. 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 by which to grade and regulate them, and 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: Indoor-use enclosures that protect internal components from solid foreign objects and contaminants (like falling dirt), and also provide limited protection to personnel by restricting their access to potentially hazardous components.


• NEMA 2: Indoor-use enclosures that restrict worker access to hazardous components, and protect the equipment stored inside against the ingress of solid foreign contaminants and dripping or lightly splashing water.


• NEMA 3: Indoor- or outdoor-use cabinets that limit personnel access to hazardous parts, and 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, and not only provide workers with a degree of protection against making contact with hazardous parts, but also protect interior components from solid contaminants, water ingress in the form of rain, sleet or snow, and the formation of ice on the cabinet’s exterior.


• NEMA 3S: 3S enclosures are used indoors or outdoors, and help to protect personnel by limiting their access to potentially harmful components. They guard enclosed equipment against the ingress of windborne and falling solid foreign contaminants, like dirt and dust, as well as water in the form of rain, sleet or snow. In addition, the external mechanisms on NEMA 3S cabinets are required to 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, as well as solid particulate like dirt and windborne dust. A NEMA 3X cabinet reduces risk to personnel by limiting access to hazardous components, provides internal components with an extra degree of protection against corrosion, and isn’t damaged by the formation of ice on its exterior surfaces.


• NEMA 4: Made for indoor or outdoor use, these cabinets and enclosures help prevent worker access to hazardous components, and guard against the ingress of water in the form of rain, sleet or snow, as well as water that is splashed or sprayed by hose. NEMA 4 enclosures prevent the entry of solid contaminants like dust and dirt, and are required to remain undamaged by the formation of ice on their outer surfaces.


• NEMA 5: Indoor-use enclosures that prevent personnel from accessing potentially dangerous components, and protect enclosed equipment from the ingress of solid foreign contaminants and objects like airborne dust, dropping dirt, lint, fibers, and fly-off particulate, as well as dripping or lightly splashing water.


• 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, whether exposed to hosing or temporary, limited-depth submersion. NEMA 6 cabinets must remain undamaged in the event that ice forms on the external surface of the enclosure.


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


• NEMA 12: Knockout-free NEMA 12 enclosures are used indoors to help restrict personnel access to hazardous components, and protect enclosed equipment by preventing 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: Indoor-use enclosures that are manufactured with knockouts and used to prevent personnel contact with hazardous components, as well as protect 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: These indoor-use enclosures prevent workers from coming into contact with potentially hazardous components, and also protect enclosed equipment against the ingress of solid contaminants like dirt, dust, circulating fibers, lint, fly-off shavings, dripping or lightly splashing water, and oil and non-corrosive coolants that seep, spray, or are splashed.

For the complete specs and details on all of the NEMA enclosure ratings, check out their NEMA Enclosure Types report.