Adding An Electrical Junction Box

by DoItYourself Staff

An electrical junction box is found among the commonly-used electrical fittings seen in residential and commercial buildings. These utility boxes are a preferred medium of facilitating safe electrical wiring. There is a lot of variety among retailed electrical junction boxes including different size offerings, mounting styles and sealing patterns. Most junction boxes are either rectangular or T-shaped. Junction boxes must be accessible but they necessarily need not be visible. Often, they are installed in roof vents or voids that are present in high-reaching walls. Junction boxes come with different terminals within them with the 3- and 6-terminal options being the most common. If a junction box will be used to support a heavy light fixture, it needs to be secured upon a structurally-strong electrical installation accessories such as joists or studs. Installing a junction box may seem like a tricky proposition but like most electrical fixtures, it is just a matter of following of some basic guidelines for a safe and trouble-free installation.

Materials Needed for Installing a Junction Box

Junction box (including the cover plate/box cover)
Linesman pliers
Standard, household pliers
Hammer
Screwdriver
Wiring fasteners
Cable connectors
Wire nuts
Power tester

Note — junction boxes are available in many sizes with different wiring capabilities and can be easily procured from electrical fitting retailers. Choose one that best suits your wiring requirements. To provide an easy insight into junction box installation, the most commonly-used format of a 2-wire junction box being installed upon the conventional wooden joist is being used below.

Installing the Junction Box

It is advisable to get started in a safe manner by turning-off the power to the circuit that will be worked upon. Turning-off the power supply could be achieved in many ways. This could mean turning-off the circuit breaker that was previously installed or simply unplugging a fuse
Using a power tester, ensure that there is no active electrical connection in the circuit
If there are any wire splices that are hanging near the circuit, place it in a protective, insulated box.
Pull the two wires in the junction box to the back, after removing the knockouts from the junction box. This helps to allow the wires to be pulled back more comprehensively.
Install the cable connectors in the voids created due to the knockouts being emptied.
Using the pliers, tighten the locknuts around the connectors. The wire should be able to slide within the connectors without too much pushing.
Once the wires have slid through, tighten them with the screwdriver.
For securing this connection, push two screws through the holes present in the back of the junction box to secure it upon the wooden joist. Fasteners can also be used to for securely mounting the box.
Using the linesman pliers, twist the wires together. Join the wires by color coordination, i.e. black with black, white with white and the bare copper wire to its counterpart and twist the wires, firmly and evenly.
Use the wire nuts to cover the wire connections. It is advisable to use the green-colored wire nuts for the bare copper or the ground wire as it conventionally symbolizes a ground connection.
Now that the wires have been covered, it is time to cover with a blank cover plate.
Check and tuck the wires into their place and cover the junction box with its cover plate.