How to Install a Three-Way Switch

If you have two or more switches to operate a single light, a three-way switch can come in handy. They are particularly convenient for placing switches at either end of a long hallway. Switches that are placed on the bottom or top of a stairwell are also the perfect examples of a three-way switch. When you look at the wiring of a three-way switch, it does not look much different from that of the common single-pole switch.

The difference between a single-pole switch and a three-way switch is that the single switch basically has two screws whereas the three way switch has a total of three connections, two on one side and one on another side. Three-way switches also have three terminals, of which one is especially marked in order to identify the one terminal that has to be placed on the other side. This marked terminal is also known as the common terminal where as the other two terminals are known as the travelers, since they are connected to two different switches and depending on the position of the switch, the current passes through either of the traveler terminals. Here’s how you can install a three-way switch.

Step 1 – Run the Wiring

Before you begin working with the wiring and switches, you need to first turn off the power supply. If you have phases of electricity in your house, switch off the phase where you will be working. If there is only one phase, you will have to switch off the mains. Next, run a power line to one of the switch boxes. Once you have wired the hot and the neutral wires to the two terminals on the switch boxes, run a third wire to the location of the other switch. Add another wire that will run from the second switch to the main light box.

Step 2 – Splice the Wires

The neutral wire in the first switch box needs to be spliced. Splice it from the switch box to the third wire that you had inserted to link the switch box to the second switch box. On the same switch box, attach the hot wire to the common terminal on the three-way switch.

Step 3 – Wire the Traveler Terminals

The conductors, both red and black, from the first cable should now be hooked to the traveler terminals of the three-way switch. Hook these two conductors to the two remaining screws on the switch in the first switch box. Now from this same wire, bring in the neutral or the white conductor to the other switch. This will be connected directly with the main lights to which the switch is connected. Again, on the second cable, the black and red terminals should be added to the remaining two screws on the three-way switch. The black conductor here has to be hooked to the common terminal.