A Complete Guide to Outdoor Electrical Closures

Outdoor electrical enclosures protect vital electrical components that are essential for keeping telecommunications systems, IT systems, and other critical technology operating safely and reliably. These enclosures are what keep complex configurations of connectors, switches, and conductors safe from everyday environmental threats like humidity, rain, snow, and chemical exposure. So, it would be an understatement to say that the type of outdoor electrical enclosure you choose is important. 

This guide covers the most common types of electrical enclosures and their industry ratings. Learn more about the differences between NEMA vs. IP ratings, why UL standards matter, and which material will best protect your electrical equipment from serious and costly damage.

Before selecting the right outdoor electrical enclosure, it’s important to understand the different ratings and certifications that may apply:

• NEMA: Considered the gold standard of electrical enclosure ratings, NEMA is a rating system for enclosures that may be exposed to rain, ice, dust, corrosion, and liquids. Each NEMA type indicates the level of protection offered, from general protection for indoor use to heavy-duty corrosion-resistant, weatherproof enclosures designed for rigorous outdoor applications. 
• IP-Rated: Much like NEMA ratings, IP (Ingress Protection) ratings indicate an enclosure’s resistance to environmental hazards. The biggest difference is that while NEMA ratings cover a wide range of criteria, IP ratings specifically identify a level of protection against dust, dirt, and moisture. 
• UL-Listed: UL-listed enclosures and cabinets have met the stringent safety and quality standards set by Underwriter Laboratories, which requires rigorous testing. 
• ATEX & IECEx-Certified: For enclosures that need to offer reliable protection against explosions in highly hazardous locations, ATEX and IECEx certifications attest to just that: electrical enclosures that are explosion-proof in high-risk environments where explosive gases or dusts may be present. 

For most outdoor applications, NEMA ratings are the most important factor to consider when choosing an electrical enclosure. NEMA enclosures are designed for hazardous conditions in industrial, utility, telecom, and infrastructure environments. 

The wrong NEMA type can mean safety risks, costly interruptions, and even total system failure. Whereas standard enclosures can promise minimal protection that may or may not hold up when tested, NEMA-rated enclosures are designed to endure environmental challenges. 

Key Considerations When Choosing an Enclosure Type for Outside Settings

Engineers have to consider every possible factor and variable when choosing the right equipment. From the likelihood of heavy rainfall to the inevitable exposure to combustible dust, every environmental consideration is critical for achieving the highest possible level of protection against dangerous safety risks and equipment failure. 

Navigating the various rating types and certifications of outdoor electrical enclosures can be significantly streamlined once you consider a few key considerations. 

Environment & Location

Most, but not all, IP- and NEMA-rated enclosures are suitable for outdoor use. There are different levels of outdoor protection, however, and it’s crucial for engineers to consider the exact location and potential environmental hazards when choosing an enclosure. For example, NEMA 4 and NEMA 4X both offer some degree of protection against solid objects and water ingress, but NEMA 4X is particularly well-suited to marine and coastal environments due to its higher level of corrosion resistance. 

Weatherproofing

Some IP-rated enclosures, like IP56 and IP57, offer protection against humidity, moisture, windblown dust, and rain. However, when it comes to harsh environmental exposure, NEMA-rated enclosures offer the broadest range of weather protection. Critical differences come down to specialized demands; for example, many NEMA enclosures perform in icy conditions where frost, snow, ice, and hail are common. IP ratings do not consider this as part of their criteria. 

Watertight Seals

Some electrical enclosures, like NEMA 4 and NEMA 12 enclosures, offer an additional degree of protection beyond weatherproofing. Gaskets on these enclosures ensure a watertight seal that prevents water ingress in outdoor environments.

Explosion Protection

ATEX and IECEX-certified enclosures, as well as NEMA 7 enclosures, cover electrical equipment that may be exposed to explosive environments where flammable gases, mists, vapors, or dusts may be present. These enclosures are ideal for industrial applications like oil refineries, rigs, and processing plants, as well as gas pipelines and distribution centers.

Stainless Steel

Stainless steel offers a number of advantages, including corrosion resistance and heat tolerance, as well as easy machining that lends itself to custom-fabricated designs. Our 304 and 316 stainless steel electrical enclosures can be manufactured to a variety of NEMA ratings, with a range of sizes and mount options. We also offer 304 and 316 ATEX and IECEx-certified enclosures that offer explosion protection and international compliance. 

Carbon Steel

Mild carbon steel is suitable for use indoors and outdoors, though carbon steel enclosures do not offer the same level of corrosion resistance as aluminum or stainless steel. We fabricate our carbon steel enclosures using hot-rolled, cold-rolled, and galvanized steel. For outdoor enclosures, we can apply a powder-coated paint finish that offers a significantly higher degree of chemical and corrosion resistance. 

Powder-Coated

Powder coating is a highly durable and attractive finishing option that can be applied to most of our metal outdoor enclosures to increase protection against abrasion, corrosion, and chemical exposure. Our powder coating process is thorough, starting with proper material preparation and resulting in an effectively cured finish coat. 

Choosing Mounting Options

Material choice and enclosure design aren’t the only considerations to keep in mind when designing your outdoor electrical enclosure installation. How your enclosure is mounted or erected plays a role in providing secure, reliable protection. Bison ProFab manufactures outdoor enclosures that can be mounted or completely freestanding. Options vary by type and material, but generally, our mount options include: 

• Wall Mount
• Pole/Tower Mount
• Pad Mount
• Walk-In
• Free Standing

Frequently Asked Questions

Are NEMA and IP ratings similar?

The key difference between NEMA and IP ratings is the criteria they cover. IP ratings focus on water ingress and solid object intrusion. An IP-rated enclosure will offer protection against dust, dirt, moisture, and debris. NEMA, on the other hand, covers a much wider range of criteria, as well as construction requirements. NEMA-rated enclosures protect against the elements, but they also offer corrosion resistance. 

What accessories are available for electrical enclosures?

Accessories vary by enclosure type, but generally include: thermostats, heaters, viewing windows, casters, fuse blocks, leveling feet, lights, power panels, and switches. 

Are outdoor electrical enclosures graffiti-proof?

Graffiti is a common concern for outdoor enclosures, especially in easily accessible locations. We offer finishes for our enclosures that provide graffiti protection. Anti-graffiti coatings are available for stainless steel, aluminum, and carbon steel outdoor enclosures.