Introduction: How to Wire a Three-way Switch
I have been an Electrician for almost 10 years. I am going to show how to wire a three-way switch. It's something that the majority of people would like to know and can be confusing.
Three Conductor Romex Wire, 14 gauge
Two Conductor Romex Wire, 14 gauge
Two single gang boxes
One light box
Two three- way switches
Two wire nuts
Philips Screw Driver
Step 1: RUN POWER WIRE INTO ONE OF THE BOXES
Feed power wire thru either one of the boxes. Should be your two conductor wire. Then strip the Romex off of wires. Make sure you can identify which wire is your power source in later steps.
Step 2: RUN THREE CONDUCTOR WIRE BETWEEN BOTH BOXES
You will run the three conductor wire from the box you just ran power to, over to your other empty box. Make sure to secure wires with staples. Strip Romex off of wires with a knife or a sharp tool.
Step 3: Run Conductor
Run two conductor wire from the box that doesn't have power in it up to the light box. this wire is called the switch leg. Also strip Romex off of wires.
Step 4: Twist Ground Wires Together
After you have all the Romex stripped free at both boxes. You will twist ground wires together, roughly six times, and cut off all but ONE GROUND wire.
Step 5: Wire Nut Nuturals Together
Take the white wires (Neutral) and strip them with wire strippers and wire nut together. Then tuck wires securely in the back of the box after wire nutting them so they are safely out of the way.
Step 6: IDENTIFY COMMON
Identify common: it is the black wire in the power box which is your hot coming from the power source. Identify common in the switch leg box, it is the black wire that goes up to the light. Wrap them around the black and red that comes from the three conductor, Which are called travelers. This will help you keep track of the common wire.
Step 7: INSTALLING THREE WAY SWITCH
You should have three remaining wires in each box. Two black and one red. Remember the black wire that you wrapped around the traveler wires is the common. Strip all three wires with wire strippers. Take your three way switch. You will see a black screw and two gold screws on the switch. The black screw is the common, which we identified in the steps above as the switch leg or hot(power source). First, bend hook in the ground wire, wrap around the green screw. Tighten securely.
Step 8: CONNECTING WIRES TO SWITCH
First take the identified in the steps earlier, the common. Put that wire to the black screw. Take additional black and red wire(travelers) and connect it to either gold screw, it doesn't matter which. You should be able to see a hole on each screw that is a wire press in fit. (Note: This only works on 14 gauge wire. 12 gauge wire you have to bend the hook around the screw. Then secure.)
Step 9: FINAL STEP
Tuck wires neatly in box. Make sure ground wire is not touching any screws. Secure switch to single gang box.
Step 10: LIGHT
This is what the end result will look like. Most important is to make sure the wiring is done correctly and you will be able to turn the light on/off with two separate switches. Watch video below for the working switch after all steps are complete.