How to Install a Junction Box: 8 Steps

Curious about how to install a junction box? A junction box is an IP box or plastic enclosure box used to cover the electrical wires. The box is typically mounted to walls, flat surfaces or similar structures.

An electrical junction box contains the connection, also known as a splice, of two or more cables. These cables must be secured to the box using cable clamps and, sometimes, conduit fittings. The junction box also includes a cover to safely enclose your wires.

Junction boxes must always remain easily accessible. Additionally, a junction box cannot be covered with drywall (or any other surface material). This box is vital because it ultimately protects your electrical connections and eliminates the risk of a fire hazard.

Here, we will provide a step-by-step guide on how to install an electrical junction box. But first, let's take a look at the dangers of an incorrect installation.

The Dangers of Incorrectly Installing a Junction Box

Many business owners may install junction boxes on their own, but there are some dangers of improperly installing them. All boxes must be installed according to the National Electrical Code. Following this code is essential to protecting you and your property. For instance, it's never a good idea to overfill your junction box with too many wires. Having too many wires inside the box can lead to overheating and issues with short-circuiting. But it can also lead to an electrical fire.

The box must also be fitted properly with the drywall. If not, materials like wood become exposed and can lead to sparks. Ultimately, if you don't install your junction box properly, you are leaving yourself, your business and your property vulnerable.

What to Know Before You Start

Installing an electrical junction box involves various essential steps. Before you get started, here are a few things to know:

• Junction box holes: Use the pre-existing holes of the junction box to mount the box and secure it to the wall.
• Wire strippers: You will need to use wire strippers to strip 3/4 inch of casing insulation at the end of every wire that you will be placing inside the junction box.
• Same-colored wires: You will need to twist the exposed ends of the same-colored wires together. Do this with the help of pliers. If you need to connect multiple wires, using a wire nut is the best option.
• Sealing the box: When sealing your junction box, push all the wires into the box. After you've done this, you can turn on the power and test your electrical system.

Step 1: Choosing the Correct Box for Your Needs

Before you do anything, it's essential to choose the right junction box for a successful installation. A junction box installed outdoors will require certain weatherproofing to be effective. NEMA 4x enclosures, designed for the outdoors, include gaskets that prevent moisture from seeping in and minimize the risk of sparks or fire.

Another factor to consider is the size of the box you need. Your junction box needs to be spacious enough for the number of wiring connections you need to make. A small box will likely be able to splice two cables but no more than this. A large box may be able to handle as many as four to six cables.

If you're undecided about which size to choose, it's best to go with a large one for a successful installation.

Choose a Standard Plastic Enclosure Box

Step 2: Prepare for Your Box Installation

Before you start any installation process, turn off the power to the circuit you are working on. Refer to your service panel, and switch off the correct circuit breaker. This will ensure that you are working safely. It's not always easy to tell whether all power has left the wires on your own. Using a non-contact voltage tester will help you determine if any voltage is left.

Step 3: Gather All Necessary Equipment

You will need specific equipment and materials to install your box. Let's take a look at everything you'll need to get started.

Equipment

• Non-contact voltage tester
• Hammer
• Screwdriver
• Pliers
• Drill-driver and screwdriver tip
• Wire strippers

Materials

• Code-approved electrical box/cover
• Wood screws
• Cable clamps
• Wire connectors

Step 4: Begin the Mounting Process

Now, it's time to start the installation process. Before mounting your junction box, you will need to separate the wires at their current splice. Be sure to loosen the cables if necessary. This allows you to make room for the junction box.

Next, you will need to secure the box to the structure. To do this, use screws and put them through the pre-existing holes. You should find these holes on either the back or side of the junction box.

What if I Have a Metal Box?

Do you have a junction box made of metal? If so, you will need to remove the metal disc on the box of each cable that needs to enter the hole. You can easily do this with the help of a screwdriver or hammer to push out each metal disc and then twist it off using pliers. You need to perform this step before separating the circuit wires.

Step 5: Prepare Clamps for Your Cables

Each cable will require a clamp. If you have a plastic junction box, you will not have metal discs. But they do contain internal cable clamps. Metal boxes typically use internal clamps. But you can install a locknut-type clamp for each cable if your metal box doesn't come with any clamps.

Insert the threaded end of the clamp through one of the holes, and secure the clamp inside the box using the ring-shaped nut. Lastly, tighten the nut with pliers.

Step 6: Secure Your Cables

The next thing you'll need to do is to secure your cables. Start by carefully pushing the cables through the clamps and into the box. Keep in mind that the cable sheathing should lengthen 1/4 to 1/2 inch into the box and beyond the clamp. The individual conducting wires typically extend about 6 inches into the box.

You might also need to trim the wires. Additionally, it's possible that you will need to strip 3/4 inches of insulation from the end of each wire with the help of your wire strippers.

To make your cables secure, tighten the screws on the clamps. Be sure not to tighten them too much, as this can cause damage. If you have a plastic junction box, you will not have to worry about tightening since these boxes usually have spring tabs.

Pay Attention to Your Wires

When securing your cables, pay attention to the condition of your wires. The end of each wire should be clean, straight, and free from damage. No more than 3/4 inch of the wire should be exposed beyond the insulation. If any wires are damaged, trim them or strip insulation with wire strippers as needed before continuing to the next step.

Step 7: Put the Wires Together

Once the wires are secure, it's time to join them together. To do this, you will need to use approved wire connectors that are mentioned in the manufacturer's instructions.

The first wires to join together are bare copper. These are green-insulated. If you have a metal junction box, remember that you will need to add a pigtail, which is 6 inches of the same type of ground wire.

Add this to the ground wire connection; then, connect the free end of the pigtail to the ground screw on the box. To join grounding wires together, you will typically need green wire nut connectors. Next, put the neutral (white) wires together. Then, put the hot (black) wires together. Use a wire nut or an approved connector for each wire pair. If you also have hot red wires, you will need to join them together as well.

Once you're done, check that all wires have been successfully put together. To do this, lightly tug on each wire to see how secure they are.

Step 8: Finish Your Installation

The last step is to carefully put the wires into your junction box. It's best to fold them in. Enclose everything with your box cover, and secure it using two screws.

According to the code, the cover is required to be a solid "blank" with no holes. Once you've done this, you're ready to bring your power back. Do this by turning on your circuit breaker, and you're finished.

Choose the Best Junction Box for the Job

Protect Your Electrical Connections With a Junction Box

A junction box is necessary anytime you have an electrical connection because all connections must be enclosed properly. If you're planning to install our Polycase junction boxes, it's essential to follow all codes, read and follow all manufacturing guides, and perform each step carefully.

Remember, never start touching wires unless you are certain that no voltage is coming from them. If you are unable to follow the steps, it's best to hire a professional who can complete the process for you.

Image Credits

Pixeliota/Shutterstock.com

mxsbmbrg/Shutterstock.com

curraheeshutter/Shutterstock.com

VITALII BORKOVSKYI/Shutterstock.com

RachenStocker/Shutterstock.com