Outdoor Plastic Junction Boxes: Pros and Cons

Choosing the right material for an outdoor junction box enclosure is a key decision in electrical design. Junction boxes protect some of the most sensitive equipment and connectors in electrical systems — from electrical wiring splices to terminal blocks. That’s why it’s so important for junction boxes to be well-designed and have the right performance specs.

Electrical junction boxes made from durable, high-grade plastics are increasingly popular. What are the common pros and cons that electrical designers and contractors should be aware of when choosing whether to use plastic junction boxes? And what can Polycase’s lineup of plastic junction boxes offer for today’s electrical applications? We’ll take a look in this article.

The Pros of Plastic Junction Boxes

Electrical plastic junction boxes are popular for a reason — they offer many unique advantages and capabilities. Some of their most notable upsides include:

1. Plastic junction boxes can often offer a more cost-effective option than steel or aluminum junction boxes.
2. For many applications, even including many outdoor ones, heavy-duty plastic such as polycarbonate offers comparable or even superior performance to metal. For example, polycarbonate is highly resistant to denting and deformation from impacts that can harm some metallic enclosures, as well as to corrosion from many common industrial chemicals.
3. Polycarbonate junction boxes from Polycase feature a wide variety of NEMA ratings, up to and including the ultra-tough NEMA 6P standard.
4. Polycase offers a line of plastic enclosures with built-in knockouts that can be easily removed with a standard screwdriver. This can make the junction box and conduit installation process considerably easier and faster.
5. Plastic enclosures are easier and more cost effective to machine, and Polycase offers custom CNC cutout machining on all of our plastic enclosure models.
6. Plastic junction boxes weigh significantly less than most metal options and can be easier to mount on poles or walls.
7. Plastic junction boxes are nonconductive, which means that the enclosure itself generally doesn’t require grounding. (However, under some circumstances, this isn’t what you want. See the next section.)

As you can see, the advantages of plastic junction boxes are numerous. However, there’s no one-size-fits-all solution, so make sure you’re also aware of their potential drawbacks.

The Cons of Plastic Electrical Junction Boxes

Plastic junction boxes aren’t right for every application. They have some important caveats that you should be aware of when making your choice, including:

1. Although Polycase offers many plastic enclosure models with great durability, in some circumstances, they won’t provide the same level of resilience that you’ll get from a stainless steel enclosure. Other enclosure manufacturers also offer less durable options such as PVC junction boxes, which can be acceptable for use as indoor outlet boxes but may not cut it for outdoor applications.  
2. Plastic junction boxes can’t be used with metal conduit, which is required for some types of electrical installation. If you’re running metal conduit through a surface-mount installation (often found in garages and other utility areas), a metal enclosure is the standard choice.
3. Plastic junction boxes are nonconductive, and the enclosures themselves do not require grounding. However, if the electrical system requires grounding through metal boxes and metal conduit, you’ll need to go with a metal enclosure for your junction box. (This is common in older electrical systems, so be careful about replacing metal junction boxes with plastic ones.)

It’s also worth noting that although some of our customers do use our boxes in residential projects, Polycase’s enclosure boxes generally aren’t intended for DIY or home improvement applications, such as the new work and old work boxes used to house light switches and outlets. Instead, we offer tough and cost-effective commercial-grade junction boxes for both indoor and outdoor use, with extensive customization options that allow our customers to create the plastic electrical boxes that fulfill their needs.

Now that we’ve covered some of the pros and cons of outdoor plastic enclosure junction boxes, let’s take a look at a few of the models available from Polycase.

Outdoor Plastic Junction Boxes from Polycase

Polycase’s electrical plastic junction box models are a great mix of price and performance. Some of the most popular models in our lineup include:

• The Polycase SK Series: NEMA 4X-rated waterproof boxes with convenient built-in knockouts for quick and simple installation. The SK Series also takes advantage of polycarbonate’s superior impact resistance by offering an IK08 impact rating, plus central bosses for easy DIN rail mounting and fiberglass reinforced construction for exceptional durability.
• The Polycase WH Series: Available in both indoor (ABS plastic) and outdoor (polycarbonate plastic) with rugged hinges for easy access to internal components and a waterproof gasket. These enclosures come standard with stainless steel mounting hardware and also offer a transparent cover option on the outdoor version.
• The Polycase ZQ Series: An ultra-tough line of weatherproof boxes that’s rated all the way up to the NEMA 6P standard to survive prolonged submersion. These models include a screw-down cover rather than a hinge and feature tamper-resistant security screws for enhanced access protection.

Polycase SK-16 model with knockouts

It’s important to weigh the pros and cons of non-metallic enclosures and to do diligent research on whether they suit your needs for an electrical junction box. But plastic junction boxes are a great option for many applications that need durability, a wide range of options and cost-effective performance. If you’ve got more questions about whether or not a plastic junction box is the right choice for you, Polycase’s enclosure experts will be glad to assist! Just give us a call at 1-800-248-1233 or contact us online for more information or a free, no-obligation quote.