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.

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.

Metallic vs. 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.

Getting 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.