August 24, 2022
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The correct type of enclosure or junction box must be specified when selecting components for a project. Building and fire codes demand that each item in the design meets or exceeds specific performance requirements.
The NEMA 3R and 4X have rating codes assigned for their performance attributes, but what is the difference between them, and how to choose? Understanding the NEMA coding system is the first step that will enable you to make an informed decision when selecting the best components. Here are the things you need to know:
What Does NEMA Stand For?
The National Electrical Manufacturers Association (NEMA), founded in 1962, is the largest electrical manufacturer trade organization in the United States. The organization represents over 300 companies and maintains manufacturing standards for electrical components for economic and safety purposes. In simpler terms, NEMA works with safety and code enforcement agencies to establish industry safety and performance standards.
NEMA produces application guides, research documents, and technical reports and maintains over 700 safety standards. Although NEMA is an American organization, its system is used in several other countries and has offices in Mexico.
An Introduction to NEMA Ratings
NEMA has established ratings for thousands of electrical components. Several factors are considered when creating a rating:
- Voltage range
- Current
- Application
- Location
- Exposure
- Environmental concerns
Components are grouped into divisions and sections. The divisions identify the application area, while the sections refer to the component type.
There are seven divisions within the code, including between two and 15 sections.
These seven divisions are:
- Building Infrastructure
- Building Systems
- Industrial Products and Systems
- Lighting Systems
- Medical Imaging and Technology Alliance (MITA)
- Transportation Systems
- Utility Products and Systems
Whereas sections include types such as:
- Wiring Devices
- Cable Trays
- Enclosures
- Low Voltage Equipment
- Motors and Generators
In the case of metallic or non-metallic electrical enclosures, the general division and section are "BI-EN":
- BI: Building Infrastructure
- EN: Enclosure
Several subsections further define specific applications.
Within the Enclosures Section of the code are the Types with which electrical professionals deal. There are currently 13 types of metallic or non-metallic building infrastructure enclosures for non-hazardous locations:
- Types 1, 2, 3, 3R, 3S, 4, 4X, 5, 6, 6P, 12, 12K and 13
And four types of enclosures for hazardous locations are:
- Types 7, 8, 9, and 10
Each enclosure type has specific characteristics that enable it to protect users from a particular set of hazards. Code numbers do not signify any distinctive feature or service level. However, higher-numbered types represent new performance requirements that have been identified.
What Does NEMA 3R Mean?
When a parts list calls for a NEMA 3R junction box, an installer may be tempted to substitute a Type 3RX enclosure. In a one-off situation, this may be fine. Over time, it would be financially prohibitive as the Type 3RX is considerably more expensive.
Polycase HD-22F NEMA 3rPolycarbonate Enclosure
The Type 3R is for indoor or outdoor applications. Like any enclosures, Type 3R protects individuals from accidental contact with energized components. It provides protection from falling objects and dirt and indirect rain and snow. The formation of ice on the exterior will not impact the unit's effectiveness. Type 3R enclosure has a drain or weep hole for any water that does accumulate to find its way out. It also includes ventilation to allow moisture to escape.
What Does NEMA 4X Mean?
NEMA 4X enclosure may be specified when collecting components for a project. Manufacturers build Type 4X enclosures with characteristics that enable them to protect the components within from damage from the surrounding environment. An electrician should be careful not to disregard the call for a Type 4X enclosure and use a Type 4 enclosure. While the difference is subtle, it is significant.
The Type 4X enclosure is suitable for indoor and outdoor applications. Aside from the primary purpose of all enclosures to protect individuals from accidental contact with electrical components, the Type 4X enclosure also protects the electrical components from damage caused by foreign objects like falling dirt and airborne dirt or dust. While the enclosure may not be waterproof, it includes gaskets that resist splashing, spraying, and falling water from rain and snow. The formation of ice on the enclosure will not impair its performance. The Type 4X enclosure offers extra protection against corrosion and corrosive materials.
NEMA 3R vs. NEMA 4X
The performance characteristics of the NEMA 3R vs. NEMA 4x enclosures make them far from interchangeable. The two units are the same in a generic sense since both provide the same level of protection to individuals that may come into contact with them. However, their NEMA ratings indicate specific features that make them suitable for different applications. The main difference is that the Type 4X provides superior protection for the component inside.
ML-34F Outdoor NEMA 4X Enclosure
A Type 3R enclosure provides general protection for the electrical devices it contains. This enclosure will protect against falling objects and dirt but does not protect against fine windblown particles like dust or other airborne contaminants. Similarly, the Type 3R only protects from falling water, like rain, sleet, and snow. It does not protect from the ingress of sprayed or splashed water. It does not provide corrosion resistance.
The Type 4X enclosure provides all the protective qualities of the Type 3R but to a higher degree. The 4X includes a seal to repel windblown dust and water. The seal will also protect the interior components from sprayed and splashed water. Finally, the Type 4X provides a level of corrosion resistance that the Type 3R does not. The Type 4X is suited to deal with more environmental factors than the Type 3R. This increased level of performance comes at a considerable cost.
Applications of NEMA 3R
It is important to understand that enclosures are ideal for general applications. When used in outdoor locations, the Type 3R enclosure provides some protection from the elements. Implementing a drain hole allows the enclosure to eliminate any condensation or incidental moisture that finds its way to the interior.
Type 3R enclosures are also excellent choices for many interior applications. The rugged construction protects individuals or objects moving around the work area from contact with energized components.
Best suited for low-dust, low-moisture environments, the enclosures have many applications for general purpose devices, such as:
- Mechanical switch box
- Junction boxes
- Lighting controls
- Equipment controls
- Communication devices
- Power monitoring devices
The NEMA 3R Enclosure is ideal for areas with low airborne dust or windblown dirt levels. Avoid areas with extreme weather exposure, pressurized water spray, or a corrosive atmosphere.
Applications for NEMA 4X
The NEMA Type 4X enclosure provides an elevated level of protection from airborne contaminants. These enclosures are fully enclosed and include rubber seals. A Type 4X is intended for outdoor exposure and is suitable for extreme indoor applications. It also provides a level of corrosion resistance.
NEMA 4X enclosures protect individuals from making contact with energized components within. The sealed enclosure resists windblown dust and dirt. They also protect against incidental water exposure, splashed, and even directly sprayed water. These features make them suited for direct exposure to rain and snow. The Type 4X is also appropriate for indoor locations subject to high dust levels or pressurized water spray. Corrosive-resistant construction materials enable the 4X enclosure to withstand corrosive atmospheres and materials.
NEMA 4X Enclosures are an excellent choice for devices such as:
- Telecommunication devices
- Common switching devices in marine environments
- Electronic control devices
- Switches and controls exposed to splashed or sprayed water
- Computer components
NEMA 3R vs. 4X: What Is Best for Your Application?
Consider environmental and corrosive exposures when selecting component enclosures for a project. Knowing the performance specification and price will lead to the right choice when assessing the difference between a NEMA 3R and NEMA 4X enclosure or junction box. The NEMA 3R enclosure will be the appropriate choice in most general-purpose applications. Consider every potential type of exposure the enclosure may encounter. If the enclosure may experience any exposure factors not covered by the Type 3R code, you must select the Type 4X enclosure.
Exposure factors to consider are:
- Exposure to direct weather
- Exposure to significant levels of dust
- Exposure to blown dust or dirt
- Exposure to sprayed or splashed water
- Exposure to corrosive atmosphere or materials
In applications that will never require a higher level of protection, the 3R is the economically sound choice. Specifying a 4X enclosure when not needed is an unnecessary financial expenditure.
Find the Right NEMA Rating for Your Enclosure
Conclusion
Specifying the appropriate components when designing any electrical system and selecting enclosures are important for safety and performance. Knowing the difference between NEMA 3R and NEMA 4X enclosures will enable designers and installers to choose a unit with the correct performance characteristics while only paying for the required features.
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