IP vs. NEMA / Weatherproof Enclosure Ratings

Understanding the necessary requirements for your product’s enclosure ratings is important, particularly when looking to gain the optimum life from your product while avoiding any safety concerns. Included below is a straight forward easy to understand overview of enclosure ratings, including IP ratings, NEMA types and the difference between the two.

We will be looking at these two common standards for industrial enclosures, what they equate to, some alternatives, and how to best choose the right one for your application.

The Europe-based International Electrotechnical Commission (IEC) has developed the IP rating standard, which stands for Ingress Protection. The National Electrical Manufacturers Association developed the NEMA rating system for classifying an enclosure’s level of protection from environmental elements.

IP standard

The International Electrotechnical Commission (IEC) is a non-profit, non-government entity that creates international standards for electrical and electronic related technologies. This organization is responsible for Publication 60526 or IEC Publication 60529 Classification of Degrees of Protection, which is also referred to as the IP code. The IP code or Ingress Protection ratings are defined in international standard EN 60529 and used to describe how well an enclosure protects against liquids and solids, such as dirt and moisture.

With the IP code, the first number is related to protection from solid intrusion while the second number is related to the level of protection from liquid intrusion. For example, an enclosure with an IP67 rating refers to a dust tight enclosure protected against immersion for up to 1m depths. Below is a table that provides an outline of the IP standards for enclosures.

IP number designations 

NEMA standard

NEMA stands for the National Electrical Manufacturers Association, one of the largest trade associations in the United States related to electrical equipment and medical imaging manufacturers. A NEMA rating is a standard created by NEMA concerning how well an enclosure protects against ingress in response to exposure to things such as liquids, dust and/or corrosive chemicals.

A NEMA rating incorporates a number, and possible letter combination, that dictates the degree of protection from hazardous parts and foreign objects, such as: dirt, water, dust, oil and/or coolant etc.

For example a NEMA Type 1, or NEMA 1, enclosure refers to a general purpose enclosure ideal for general indoor use with the lowest protection against the items listed above. NEMA type 9, or NEMA 9, is a Class II indoor hazardous location explosion-proof enclosure to be used for E, F or G environments.

NEMA Ratings

NEMA 1
Indoor use primarily to provide a degree of protection against limited amounts of falling dirt.
NEMA 2
Indoor use primarily to provide a degree of protection against limited amounts of falling water and dirt.
NEMA 3
Outdoor use primarily to provide a degree of protection against rain, sleet, windblown dust and damage from external ice formation.
NEMA 3R
Outdoor use primarily to provide a degree of protection against rain, sleet, and damage from external ice formation.
NEMA 3S
Outdoor use primarily to provide a degree of protection against rain, sleet, windblown dust and to provide for operation of external mechanisms when ice-laden.
NEMA 4
Indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, hose-directed water and damage from external ice formation.
NEMA 4X
Indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, hose-directed water, and damage from external ice formation.
NEMA 5
Indoor use primarily to provide a degree of protection against settling airborne dust, falling dirt, and dripping noncorrosive liquids.
NEMA 6
Indoor or outdoor use primarily to provide a degree of protection against hose-directed water, and the entry of water during occasional temporary submersion at a limited depth, and damage from external ice formation.
NEMA 6P
Indoor or outdoor use primarily to provide a degree of protection against hose-directed water, the entry of water during prolonged submersion at a limited depth, and damage from external ice formation.
NEMA 7
Indoor use in locations classified as Class I, Division 1, Groups A, B, C or D hazardous locations as defined in the National Electric Code (NFPA 70) (Commonly referred to as explosion-proof).
NEMA 8
Indoor or outdoor use in locations classified as Class I, Division 2, Groups A, B, C or D hazardous locations as defined in the National Electric Code (NFPA 70) (commonly referred to as oil-immersed). 
NEMA 9
Indoor use in locations classified as Class II, Division 1, Groups E, F and G hazardous locations as defined in the National Electric Code (NFPA 70) (commonly referred to as dust-ignition proof).
NEMA 10
Intended to meet the applicable requirements of the Mine Safety and Health Administration (MSHA).
NEMA 12
Indoor use primarily to provide a degree of protection against circulating dust, falling dirt and dripping non-corrosive liquids.
NEMA 12/K (enclosures with knockouts)
Indoor use primarily to provide a degree of protection against circulating dust, falling dirt, and dripping non-corrosive liquids.
NEMA 13
Indoor use primarily to provide a degree of protection against dust, spraying of water, oil, and non-corrosive coolant.

WEATHERPROOF

There are instances where manufacturers will list their products as weatherproof or explosion-proof without necessarily listing a NEMA or IEC “IP” rating.

These products may have been tested to alternative standards, such as Underwriters Laboratory (UL) standards, but do not necessarily conform to a specific NEMA type or IP rating.

This may also be applicable to an application that calls for a general confirmation that the unit can withstand basic outdoor environmental factors, such as rain or indoor wash-down applications.

For example, Dwyer Instruments, Inc. Flotect® Flow Switches feature weatherproof enclosures. Weatherproof is a term used to describe a unit that was tested by the Underwriters Laboratory and proven to withstand water exposure by performing a Hosedown Test according to SEC. 35 OF UL 5. In this test, samples of the enclosure are sprayed with hose water at a definite flow rate and a specified distance for a quantified duration at the joints.

If a product is listed as weatherproof or explosion-proof with no specific ratings, be sure to request the method for testing. You may find that the unit still fits your application needs without a specific IEC “IP” or NEMA rating. This can save both time and money.

IP vs. NEMA

IEC Enclosure Classification Designations or the IP code rating only focuses on protection against solids and liquids and does not specify protection capabilities against instances of explosions, condensation, or corrosive vapors as NEMA does. Consequently even though NEMA tends to be amore of a U.S. standard, in comparison to the IEC standard of IP, it cannot easily be converted from one enclosure type to the other.

As can be seen above, NEMA 1 (general indoor use) may equate to IP00 (no special protection from solids and liquids), but IP66 (dust tight and protection against power water jets) does not translate to NEMA 4X (dust tight with protection against hose directed water and corrosion resistant). Nonetheless, as NEMA does include additional degrees of capabilities, you can typically cross over NEMA to some level of IP, but not IP to NEMA. There is unique protection that NEMA tests for that IEC does not.

It is imperative to first understand the requirement of your unique application. General use indoor applications will call for vastly different requirements than units placed outdoors in hazardous environments. Understanding these requirements and the difference between enclosure ratings will save not only money, but will avoid premature product failure and prospective safety concerns.

IP vs. NEMA ratings table

There is not a direct correlation between IP ratings and NEMA ratings, as the two systems are based on a different set of variables. However, the table above shows an approximate cross reference that can be used to help determine the IP number that meets or exceeds a particular NEMA rating. 

One thing that’s confusing about this matchup is that, unlike IP ratings, NEMA rating protection does not always increase with higher numbers. For instance, NEMA 12 provides less protection than NEMA 4. Another confusing point is that some NEMA ratings include additional letters to signify special qualities. A good example is NEMA 4X: the X indicates corrosion resistance.