Understanding NEMA Ratings: Definition, NEMA Chart, And FAQS
NEMA ratings are commonly printed on electrical enclosures and equipment or supplied in supporting documentation. You will find them on nearly all electrical systems and electrical pieces of equipment.
In this article, we will take a look at what NEMA ratings are, who created them, what each rating means, and some more FAQs. So let’s get into it, what are NEMA ratings?
NEMA ratings are numeric standards that have been created by the National Electrical Manufacturer Association. NEMA ratings give a recommendation of where electrical panels and systems can be safely used and what environments may suit them. NEMA ratings range from NEMA level 1 up to NEMA level 13.
Their website is www.nema.org, more information can be found on their site.
NEMA ratings are firstly graded by a number that can be followed by a letter in some cases. The NEMA rating scale starts from NEMA level 1 all the way up to NEMA level 13. NEMA ratings do not however work on a scale from top to bottom, each NEMA rating should be read individually and checked if it is ideal for the intended environment.
Electrical enclosures or equipment are given a NEMA rating depending on the level of protection that they can offer. By using NEMA ratings it makes it extremely easy for the end-user to decide whether an enclosure or piece of electrical equipment is suitable for use in their intended environment.
The term NEMA actually refers to the National Electrical Manufacturers Association which is one of the largest trade associations for electrical equipment manufacturers in the United States.
NEMA ratings are kind of like IP ratings which are found in the United Kingdom and across Europe.
The NEMA Rating Chart Or System
NEMA ratings start at level 1 all the way up to NEMA level 13. Each NEMA rating means a different level of protection, some will protect against dust ingress, some water ingress, and some both.
The NEMA rating required for a specific application tends to differ and depends on a number of environmental factors.
| NEMA Rating | Description | Environmental Requirements | Mechanical Requirements |
| NEMA 1 | Indoor use | Dust-tight | Basic protection |
| NEMA 2 | Indoor use | Drip-tight | Basic protection |
| NEMA 3 | Outdoor use | Rain-tight | Basic protection |
| NEMA 3R | Outdoor use | Rain-tight | Protection from falling ice and sleet |
| NEMA 4 | Outdoor use | Water-tight | Protection from falling ice and sleet |
| NEMA 4X | Outdoor use | Water-tight | Protection from corrosion |
| NEMA 6 | Submersible | Water-tight | Protection from corrosion |
| NEMA 7 | Explosion-proof | Protection from ignitable dust, and fibers | Protection from mechanical damage and corrosion |
| NEMA 8 | Explosion-proof | Protection from ignitable gases and vapors | Protection from mechanical damage and corrosion |
| NEMA 9 | Explosion-proof | Protection from ignitable gases, vapors, and dusts | Protection from mechanical damage and corrosion |
| NEMA 10 | Explosion-proof | Protection from ignitable dusts | Protection from mechanical damage and corrosion |
| NEMA 11 | Explosion-proof | Protection from ignitable fibers | Protection from mechanical damage and corrosion |
| NEMA 12 | Indoor use | Dust-tight | Protection from dripping water and non-corrosive liquids |
| NEMA 13 | Indoor use | Dust-tight | Protection from dripping water and oil |
This table is just a small sample of the many NEMA ratings that are available. Depending on your specific application and environment, there may be other NEMA ratings that are more suitable for your needs.
We will now take a look at the NEMA rating system and also what each NEMA rating means.
NEMA 1
A NEMA rating of 1 is a general-purpose rating. It protects against light, indirect splashing, and dust (not dust-tight). Typically used to prevent contact with live parts and used indoors under normal atmospheric conditions.
NEMA 2
A NEMA rating of 2 can be known as a ‘drip tight’ enclosure or piece of electrical equipment. It is similar to NEMA 1 but has additional properties such as drip shields. This type of NEMA rating is typically used in locations where condensation may be present.
NEMA 3
A NEMA rating of 3 is weather-resistant. Protection against falling dirt or dirt that is windblown, against weather hazards that include rain, sleet, and snow. Also protection against the formation of ice. Typically used outdoors on site, in shipyards, tunnels, and on subways.
NEMA 3R
Just like NEMA 3 but also omits protection against dust that may be windblown.
NEMA 3S
Just as NEMA 3 but also operable when the equipment or enclosure may be laden with ice.
NEMA 3X, 3RX, 3SX
Just like NEMA 3 but the X indicates that it has additional protection against corrosion. Typically used on applications near salt water.
NEMA 4 And 4X
NEMA 4 rating is classified as watertight. The actual grading specifies that it must exclude at least 65 GPM of water from a 1-inch nozzle that is delivered from a distance not less than 10 feet for 5 minutes. This is typically used outdoors in shipyards, factories, water treatment plants, and on transportation. The X added to the NEMA rating shows that it has additional resistance to corrosion.
NEMA 5
A NEMA 5 rating means dust-tight. Equipment or enclosures normally are supplied with gaskets or seals which exclude dust. Typically used in cement plants, mills, or anywhere where high levels of dust are found.
NEMA 6 And 6P
A NEMA 6 rating means that an enclosure or piece of equipment is submersible. The design of these enclosures and equipment depends on factors such as pressure and the amount of time that it may be submerged.
A rating of 6 means it can be temporarily submerged whereas 6P can withstand occasional prolonged periods of being submerged. Neither of the NEMA 6 and 6P ratings is intended for continuous submersion. Typically found in quarries, mines, and manholes. Can be used with water and oil.
NEMA 7
A NEMA 7 rating means that it is certified and labeled for use in areas that can contain specific hazardous conditions. They can be used in locations indoor that are classified as Class I, Groups A, B, C, and D which are defined in NFPA standards.
NEMA 8
A NEMA 8 rating means that it is certified and labeled for use in areas that can contain specific hazardous conditions. They can be used in locations indoors and outdoors that are classified as Class I, Groups A, B, C, and D which are defined in NFPA standards such as the NFPA 70 standards.
NEMA 9
A NEMA 9 rating means that it is certified and labeled for use in areas that can contain specific hazardous conditions. They can be used in locations indoors and outdoors that are classified as Class II, Groups E, F, and G which are defined in NFPA standards.
NEMA 10
A NEMA 10 rating is suitable for the MSHA standards and meets the requirements outlined in the Mine Safety and Health Administration 1978 standard.
NEMA 11
A NEMA 11 rating is a general-purpose rating that offers protection against the corrosive effects of liquids and gases. They meet drip and corrosion resistance test standards.
NEMA 12 And 12K
A NEMA 12 and 12K rating is a general-purpose rating that is intended for indoor use. They provide some protection against dirt, falling dirt, and dripping liquids that are non-corrosive. They meet drip, dust, and rust resistance test standards.
NEMA 13
A NEMA 13 rating is a general-purpose rating that is used to protect against dust, spraying of water, and non-corrosive coolants. They meet oil exclusion and rust resistance design test standards.
FAQs
What NEMA Rating Is For Outdoor Use?
As you can see from the list of NEMA standards above there are many different ratings that are suitable for outdoor use.
NEMA rating 3, NEMA rating 3R, NEMA rating 4, NEMA rating 4X, NEMA rating 6, and 6P are typically the most ideal types for outdoor use. These are the most common NEMA ratings you will find for typical items to be used outdoors.
Whilst some other NEMA ratings can be used outside they can be more expensive as they are typically found on specialist equipment that has typically been designed for industrial or specialist use.
What NEMA Rating Is Waterproof?
NEMA rating 3, NEMA rating 3R, NEMA rating 4, NEMA rating 4X, NEMA rating 6, and 6P are all waterproof ratings and the most common types you will come across.
Whilst all of the above NEMA ratings are waterproof they all offer different levels of protection against water ingress. NEMA ratings 3 and 3R are ideal for outdoor use but only when they may come into frequent contact with rain, sleet or snow. NEMA 4 ratings are practically the same as NEMA 3 ratings however they protect against hose-directed water.
This makes them ideal for applications such as factories and car washes. NEMA 6 and 6P ratings are among one the most watertight and durable protection that a panel or piece of equipment can offer. They have everything a NEMA 4 rating can offer you but also offer protection against occasional temporary submersion.
What Is The Lowest NEMA Rating?
The lowest NEMA rating is NEMA level 1. NEMA level 1 is given to general-purpose electrical enclosures and pieces of equipment. They are generally splashproof to droplets and resistant to low levels of dust.
What Is The Highest NEMA Rating?
The highest NEMA rating is NEMA level 13. NEMA level 13 will be given to pieces of equipment or enclosures that are water-resistant, fully dust-proof, and resistant to non-corrosive coolants.
Why Were NEMA Ratings Created?
The NEMA rating chart (or system) has been created so you can easily find out what each level of NEMA rating means and where enclosures and equipment are suitable for use.
By Liam Cope
Founder, Engineer Fix