Adding a Switch to an Existing Circuit: A Step-by-Step Guide
Learn how to install a switch in the middle of an electrical circuit to control devices on that circuit. This guide covers the tools needed and the steps to safely cut wires, strip insulation, and connect the switch.
By Hayden Hayes6 steps
A light switch can be added to an existing circuit.
If you want to add on/off control to devices already on an electrical circuit, you can do so by installing a light switch in the middle of that circuit. This requires only basic tools and some wiring know-how.
Step 1
Shut off the power to the circuit at the breaker or fuse box. Working on an energized circuit is dangerous and should never be attempted.
Step 2
Using wire cutters, cut the wire. Then take the black and white wires from both cut ends and use wire strippers to remove 1/2 inch of insulation from each.
Step 3
With a flat-bladed screwdriver, loosen the terminal screws on each side of the switch. Turn them out until there is a 1/4-inch gap between the screw heads and the switch contacts.
Step 4
Take the black and white wires from one end of the cut wire and place them under the screws on the right side of the switch. The black wire goes under the brass screw, and the white wire goes under the silver screw. Then tighten the screws to secure the wires.
Step 5
Take the black and white wires from the other end of the cut wire and place them under the screws on the other side of the switch. Again, the black wire goes under the brass screw and the white wire under the silver screw. Tighten the screws to hold the wires in place.
Step 6
Restore power to the circuit.
