The National Electricals Manufacturer Association (NEMA) can be termed as the largest and most prominent association of the manufacturers of electrical equipment in North America. NEMA also has certain guidelines for the enclosures and panels that are to be used in industrial applications. The ratings of the electrical enclosures give a clue about the extent to which personal access may be restricted to the hazardous components. The ratings also provide information about the environmental conditions where the enclosure should be used and what capability they have to offer protection in the different operational, weather and environmental scenarios. For instance, an enclosure with NEMA rating 2, may depict the weather conditions the enclosure may provide protection against including, temperature and humidity among others. The rating may also throw light on the corrosive agents (for instance gasoline or acetylene) that the enclosure can resist.
The NEMA ratings for different enclosures
The NEMA ratings can be used to know more about the characteristics of an enclosure, but not its size and other aspects. After evaluating the rating, one can decide the best and proper way of using the enclosure. One can place the right kinds of equipment inside the enclosure and also choose the best one for given weather and operational conditions when he or she is aware of the rating.
NEMA 1
These electrical enclosures can be used indoors only. They offer protection against dirt and do not allow the solid particles to infiltrate and reach to the insides of the enclosure. These enclosures may offer limited resistance to light and water, and to indirect splashes as well. But the primary aim of their installation is to prevent contact with the live components. They can be used in normal weather conditions.
NEMA 2
These enclosures are also used indoors and offer limited protection against the dirt, light, and water (such as splashing or dripping). They are drip-tight and therefore can be used in laundries and the cooling rooms where condensation rates are high.
NEMA 3
These enclosures can we use outdoors and offer protection against sleets, rain, dust, and other weather elements. Ice formation does not damage them. They are used in tunnels, subways, construction work, and on ship docks, among other outdoor areas.
NEMA 3R
The enclosures resemble the NEMA 3 enclosures except that they do not offer protection against windblown dust. They are devoid of gasketing.
NEMA 3S
The resistance of these enclosures to the external agents and weather conditions does not deteriorate even when they are laden with ice. They offer advantages resembling those offered by the NEMA 3 enclosures only and may be used in the coolest and most freezing of conditions.
NEMA 3X/3RX/3SX
These enclosures offer better protection against the corrosive agents while also having all other properties and benefits of the NEMA 3 series electrical enclosures.
They may be used near the saltwater conditions.
NEMA 4
The electrical enclosures can be used outdoors. They offer protection against rain, sleet, snow, windblown dust, and other elements. Apart from resisting splashing of water, they also keep the equipment safe from hose-directed water. They are not disturbed by ice formation on their exteriors. These are essentially watertight and may be used in areas including water treatment, dairies, and ship docks.
NEMA 4X
Apart from having all other properties and qualities of the NEMA 4 electrical enclosures, the 4X variety may offer greater resistance to corrosive agents.
NEMA 5
The dust-tight electrical enclosures are used indoors. They offer protection against the non-corrosive liquids, dirt, and airborne dust.
NEMA 6 and 6P
These enclosures can be used both indoors and outdoors. They can withstand the temporary submersible conditions and therefore may be used in mines and other areas.
NEMA 8
These enclosures are used both indoors and outdoors and are suitable for hazardous conditions.
NEMA 9
Can be used in specific hazardous conditions. The NEMA 8 and 9 enclosures are used for the specific NFPA (National Fire Protection Association) hazardous material classes and groups.
NEMA 10
The enclosures/panels are intended for their use in accordance with the MSHA (Mine Safety and Health Administration) guidelines.
NEMA 11
The general purpose enclosures have good resistance to a wide range of corrosive agents.
NEMA 12
The enclosures are used indoors and offer a basic level of protection against dust, and the dripping and non-corrosive liquids.
NEMA 13
General purpose enclosures that offer resistance against the non-corrosive coolants, dust, and water.
Always choose the right rating for your enclosure after careful evaluation the weather, hazardous, environment and other conditions.