How to Install an Electrical Junction Box
Step-by-Step Instructions for Installing
Electrical Junction Boxes
By Mark J. Donovan
When splicing or joining electrical
wires to feed power to electrical devices, it is unacceptable to simply wire-nut
twist the wires together and leave them exposed behind a wall. An electrical
junction box is required for this type of situation per the National Electrical
Code. Installing electrical junction boxes is easy to do, and they are very
affordable so there is no valid reason to not use them. On the contrary, there
is every reason to install them when splitting or joining electrical wires.
First and foremost an electrical
junction box protects humans from the threat of an electrical shock or fire.
They also protect the electrical connections from becoming damaged by dust,
water and other objects that could come in contact with them.
The first step to installing an electrical junction box is to select the right
one for the job. Make sure you pick one that is appropriately sized for the size
and number of electrical wires and connections you need to make in the junction
box. Also, make sure to select a junction box that meets the environmental
application. The National Electrical Manufacturers Association (NEMA) has a
rating system for junction boxes, so make sure you select one per their rating
After selecting the appropriate
electrical junction box, mount it to the wall, or wall studs with the
Next, pull electrical wires into the installed electrical junction box. Make
sure to pull the wires into the box so that 6 inches of each wire bundle (Romex
cable) hangs out of the box. Also, make sure they are all of the same size.
Never connect different gauge wires together as this can lead to an electrical
Then cut away the protective
sheathing from each Romex wire bundle to expose the separate ground, white and
Then, using wire strippers, strip
back each white/black/red wire about 5/8 to ¾ of an inch.
Next, twist the appropriate exposed copper wire ends together in a clockwise
direction, and then cover each twisted pair with a wire nut.
If you are installing a metal junction box, attach a ground wire pig tail to the
exposed ground wires that you twisted together in the electrical junction box,
and fasten the other end of the ground pigtail to the metal junction box
Then carefully push all of the wires into the installed electrical junction box,
making sure not to break any wires in the process.
Finally, seal the electrical junction box with its cover plate to complete the
electrical junction box installation.
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