What Is a Junction Box Used For? Evaluating Commercial Uses

Almost every modern electrical system requires junction boxes. Commercial electrical systems, however, are frequently exposed to more demanding conditions than residential systems. For commercial applications, it’s important to specify junction box models that are built to a tougher standard and equipped with commercial-grade features.

What is a junction box used for in commercial applications today? How can you find a junction box that aligns with the needs of your application? Ahead, we’ll talk about some of the most common commercial use cases for junction boxes. We’ll also show you some highlights from Polycase’s selection of enclosures that offer ideal solutions for protecting your wiring!

What Is a Junction Box Used For in Commercial Applications?

A junction box is an electrical enclosure that houses one or more wiring connections. The box protects the connections, which usually contain vulnerable points such as wire splices, from environmental conditions and accidental contact. As you’ll read in our junction box guide, any point at which two wires join should be protected by a junction box.

That makes junction boxes equally important in commercial applications as they are in residential contexts. However, commercial junction boxes often need to fulfill a much wider range of specifications than residential boxes. Fortunately, Polycase offers a full range of enclosures designed for great performance in commercial junction box applications.

To get the right level of protection when choosing an enclosure, businesses need to look at the specific requirements of their use cases. In the next sections, we’ll examine some of the must-know factors, starting with the major decision of which material you need to use.

Should You Choose Metallic or Plastic Junction Boxes?

Junction box enclosures can be made either of metal (usually aluminum or stainless steel) or plastic (usually polycarbonate or ABS). Choosing between plastic and metallic junction boxes is one of the first big decision points when specifying an enclosure type for a commercial application.

The choice depends on which cable and conduit materials you’re using. Metal-sheathed cable and metal conduit usually require a stainless steel junction box to provide grounding. Plastic junction boxes are the standard choices for non-metallic cable. Polycase offers both metallic and plastic junction box options, and we’ll look at some top options for both later on.

How Do You Get the Right Size Junction Box?

The size of the junction box itself is also a relevant factor in making your choice. We cover this topic in depth in our guide to junction box size, including the National Electrical Code’s standard sizes for junction boxes. Commercial junction boxes are typically larger than residential junction boxes, since they’ll often contain more connectors at once.

To sum it up, you’ll need to consider the following:

• Box volume: The total space enclosed by the box.
• Box fill: The total size of the components inside the box.

What Are the Essential Features for Commercial Junction Boxes?

Material and size aren’t the only two factors to think about when choosing a commercial junction box. The enclosure features that we’ll discuss below are also relevant in many different commercial applications.

What is a NEMA Rating or IP Rating?

These two rating systems measure the protective qualities of electrical enclosures, including junction boxes. (Read our NEMA vs. IP guide to understand the differences!) Basically, these enclosure ratings allow you to choose an enclosure that offers the level of protection your wiring connections require.

Check local commercial electrical codes to learn if you need to use junction boxes with a specific NEMA or IP rating. In most cases, the commercial electricians and engineers who are working on your electrical system will be able to point you to the right NEMA or IP rating as required by local codes.

Why Use Custom Cutouts/Knockouts?

By definition, junction boxes almost always require cutouts and/or knockouts in order to fulfill their function. Most junction boxes will need cutouts for cables and conduits to enter and leave the enclosure. However, this also means making sure that the enclosure maintains its NEMA or IP rating where the cables enter or exit.

Polycase’s custom CNC machining options make it easy to get the exact cutouts that you need on your commercial junction boxes. What’s more, we offer several different models of cable glands for protecting cable entries into enclosures. For truly instant customization, we offer the SK Series, with built-in knockouts designed to fit standard cable sizes.

How Can Digital Printing Help?

Junction boxes in commercial systems often need to be marked with identifiers or instructions. Technicians might need to know which specific connections a junction box houses or which boxes require extra safety precautions. For this reason, businesses may hire specialty printing companies to customize their junction boxes, or they may print labels and attach them in-house.

Polycase offers an easier and faster way to get custom HD printing on your junction boxes. We offer brilliant full-color digital printing on many different enclosure models. In addition, we print with scratch- and fade-resistant inks to ensure that all designs remain sharp and legible for as long as possible.

What are the Benefits of Hinged Covers?

Some connection points need to be easily accessible to technicians for troubleshooting, especially junctions that supply power to critical system components. Enclosures with hinged covers make excellent junction boxes for these applications.

Fortunately, Polycase’s hinged enclosures give you these benefits without sacrificing security and protection. An enclosure with a hinged cover can still be waterproof and/or dustproof with the addition of a gasket seal on the door. For security, we include built-in lock hasps on our hinged enclosures to allow easy attachment of a padlock.

Which Surface Mounting Hardware Is Available?

Commercial junction boxes are usually mounted on walls or other flat surfaces, and you’ll need mounting hardware to attach the junction box securely. Mounting feet and flanges are some of the most common and practical ways to add mounting hardware to an electrical junction box.

Some Polycase enclosure models come with mounting feet, flanges or other hardware already attached. In other cases, the buyer can equip the enclosure with a set of screw-on enclosure feet. If you choose an enclosure model that uses surface mounting accessories, make sure to purchase accessories that are designed to work with the model you’re using.

What Is a UL 94 Flame Rating?

A UL 94 flame rating measures a material’s ability to self-extinguish when exposed to an open flame. This can be a key characteristic for commercial junction boxes since it helps prevent electrical fires from spreading. The highest UL flame rating (UL 5VA) denotes a completely non-flammable box, while the lowest (UL H-B) slows the burn rate but does not self-extinguish completely. See our guide to UL 94 flame ratings for a full explanation.

What Are Common Commercial Applications for Junction Boxes?

Most commercial electrical systems have multiple junction boxes, and large systems may have hundreds or thousands of them. But how do institutions integrate and deploy these boxes within their electrical systems?

The answer to that question depends on the specific conditions of the application. Let’s look at some common applications for commercial junction boxes and how the specific hazards of each environment determine the type of box you’ll need.

1. Office and Retail

Commercial office and retail buildings are typically the least demanding applications for junction boxes. However, these applications still need basic protection against unauthorized access and accidental contact, and they also usually need junction boxes with more space than you’ll find in standard residential boxes.

Sometimes, these applications don’t require NEMA or IP enclosures. Other times, an indoor rated model like a NEMA 1 enclosure or NEMA 12 enclosure will be an appropriate choice. However, outdoor junction boxes might still be required in areas that will be exposed to adverse conditions. Specifying a junction box that slightly exceeds requirements can be a smart strategy for building resilience into a system.

2. Warehouses and Distribution Centers

Most warehouses and distribution centers aren’t subject to harsh environmental conditions, but they’re demanding applications nonetheless. These facilities often use a lot of electricity to power lighting systems, climate control and other essentials.

Commercial enclosures for warehouses and DCs need:

• An impact-resistant build.
• Enough space to accommodate large numbers of connections.
• Often a UL 94 flame rating.

3. Marine Environments

Marine applications such as cargo ports, marinas or seafaring vessels are among the most demanding for any type of electrical component. Electrical connections in these areas have to withstand waves, wind, corrosive salt water and possibly even submersion.

It’s thus not surprising that these environments call for enclosures rated at the highest level of the NEMA and/or IP scales. NEMA 4X junction boxes are particularly common thanks to their corrosion resistance, and NEMA 6P enclosures are also popular for their extreme water ingress protection.

4. Manufacturing Facilities

The manufacturing industry requires extremely reliable and well-protected electrical systems. High voltage loads are often distributed through extremely complex systems across numerous branch circuits. Many manufacturing facilities also present hazards like flying debris and splashing water.

All of these factors can add up to an extremely demanding set of conditions. NEMA 12 enclosures are a good choice for less strenuous manufacturing environments. More hazardous environments, on the other hand, may need outdoor rated boxes like NEMA 3R enclosures or NEMA 4X enclosures. Finally, manufacturing is another sector in which a UL 94 flame rating is often required.

5. Medical Facilities

Medical facilities also have large and complex electrical systems that require tough junction boxes. Reliability and ease of access are particularly important in medical applications, since an electrical failure can put lives in danger.

Indoor junction boxes, such as NEMA 12 enclosures, are common choices for medical facilities. However, many medical facilities are also part of large medical campuses with multi-building electrical systems. In such cases, outdoor rated enclosures (often buried underground) are an essential part of a safe and functional local power grid.

What Are The 5 Best Commercial Junction Boxes from Polycase?

Polycase is a leading supplier of commercial electrical enclosures, including indoor and outdoor junction boxes. In this section, we’ll highlight some of our most popular electrical junction box models.

1. What are the features of the Polycase ZQ Series?

For all-around outdoor-grade junction box performance, the ZQ Series provides unbeatable value. These models are molded from impact-resistant polycarbonate, which is easily modified with any custom cutouts you need. A full range of ZQ Series accessories like cable glands make it simple to equip your junction boxes for almost any conditions, and the NEMA 6P ingress protection protects it against even the roughest conditions.

2. Why choose the Polycase ZH Series?

Our ZH Series models are hinged polycarbonate NEMA 6P enclosures built to offer versatility in commercial applications. With stainless steel latches and a built-in lock hasp, the ZH Series is as secure as it is sturdy. It’s also incredibly easy to customize to your specifications, thanks to our robust in-house customization options.

3. How does the Polycase SK Series offer versatility?

The SK Series comes with pre-cut knockouts that offer quick and versatile customization for almost any junction box configuration. These knockouts are simple to remove with a standard screwdriver, and SK Series accessories such as cable glands make it simple to maintain the protective rating required.

4. When should you use the Polycase AN Series?

Need a metal junction box that’s built to stand up to the rigors of commercial applications? Polycase’s AN Series aluminum enclosures could be the ideal choice. These durable die cast aluminum boxes offer all the reliability that commercial grade junction boxes require, and they’re rated up to NEMA 6P for performance under even the most strenuous conditions.

5. What makes the Polycase SA Series stand out?

SA Series stainless steel enclosures are among our toughest and most elegant junction box options. They’re constructed from high-quality 304 stainless steel, and their NEMA 4X rating means they’ve been tested for superior corrosion resistance. The SA Series are also among our most secure enclosure models, thanks to the inclusion of a built-in keyed latch.

Polycase SK-12 Polycarbonate Enclosure with Knockouts

Polycase takes pride in offering the friendliest and most knowledgeable customer service of any enclosure manufacturer. We’ll be happy to assist you with designing and selecting a junction box for your commercial application! Just call us at 1-800-248-1233 or contact us online for a free quote on your customized junction boxes.

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