Just like a junction on the street an electrical junction box is used to connect wires together and route them to where they need to go. Junction boxes are meeting points of multiple connections called branch circuits. These connections are usually the end of a conduit run. A junction or conduit box also makes it easy to access these wires as all they’re protected by is a small plastic or metal covering. A j box is used to keep wires safe from external factors such as the elements.
By having wires inside a junction box you also keep them away from unwanted tampering. They don’t just get installed by electricians, because they are so simple that even someone without any major knowledge about electricity or electrical equipment can install them. Be it hooking up some LED downlights or outlets, a junction box can be quite helpful in priding the necessary means of connecting fixtures to the electrical installation in your household.
Are Junction Boxes Safe?
Installing a junction box alone isn’t going to guarantee safety, you must ensure that you have combustible materials away from it. The best practice of making sure that j-boxes are safe is to install them flush with the drywall. A safe conduit box is one that is also placed not too far into the wall.
How to Install a Electrical Junction Box
What You Need
To make sure that the installation process of your junction box goes well you’ll need to gather some tools and materials, such as a screwdriver, wire strippers, a hammer, pliers, a drill and screwdriver tip, non-contact voltage tester, wood screws, wire connectors, cable clamps and a code-approved electrical box and cover.
Preparing to Work
Before you get started, you’ll need to ensure that the coast is clear by shutting off the power to the circuit and by testing all the wires you’ll be working with a non-contact voltage tester. Once there is no voltage showing up on the wires, you can go ahead and start working on the j box by removing a knockout on the box for each cable that will go inside it. Twist off the knockout disk using the pliers.
Mounting the J Box
After everything is ready to go, start separating the circuit wires at the splice and then loosen the cable as much as needed so there’s enough room for the junction box. To mount the j box, you usually need to anchor it to the framing by using the screws that are driven through the box’s factory-made holes, found either in the back or side of the box.
Setting Up the Box
After the box has been mounted, you’ll need to install a cable clamp for each cable that goes into the box. This is if you should use a standard plastic electrical box since they do not have knockouts, but rather internal cable clamps. If your metal box doesn’t have internal clamps, make sure to install locknut-type clamps. Do this by inserting the threaded end of the clamp through the knockout hole and then secure it inside the box with a rich-shaped nut. Make sure to tighten the nut using the pliers.
Securing the Cables
Next, you’ll need to secure the cables by feeding them into the box with the cable sheathing extending anywhere from 6mm to 1.2cm beyond the clamp. The individual conducting wires need to be extended about 15cm into the box. If needed, trim the wires by stripping about 2cm of insulation from the end of each wire with wire strippers. To secure the cables, tighten the screws on the clamps but be careful not to overtighten the cables, as this can end up damaging them. Plastic j-boxes will usually have spring tabs for the clamps which means they won’t require any tightening.
Joining the Wires
Using approved wire connectors, join the wires together following manufacturer instructions. You usually need to start joining the bare copper ground wires first, and if the box is metal you need to add what is known as a pigtail. This is an additional 15cm of the same type of ground wire to the ground wire connection. The loose end of the pigtail needs to be connected to the ground screw found on the box.
Then, you typically join the neutral wires together and after that, you need to join the hot wires together. For each of these pairs of connections, you need to use a wire nut or an approved connector. If there are hot wires red in colour, then you’ll need to join them too. Once all the wires are joined together, make sure to check the connections by tugging each wire gently.
As the very last step, you’ll need to fold the wires carefully into the box. Then, install the cover of the box which usually needs to be secured with two screws. The cover must be blank and without any holes. With the cover on, bring back the power to the circuit and you’re all good.