Even if a 3-way switch connection is a bit complicated, it comes in handy when you require to control a light bulb from two places. Do you know how to wire the 3-way switch? What is the common wire on a 3 way switch? How do I find the common wire on a 3-way switch?

Well, a 3-way switch connection is definitely complex as compared to any single-way switch connection. There are lots of wiring required to flow electricity from the source to both of the load.

The hot black wire carries electricity from the supply to the first switch in a three-way switching setup. This is known as the “Common Wire” or the “Line Wire”. The wire always flows electricity unless the breaker is turned off.

This article discusses how a 3-way switch is wired in detail.

Let’s start then!

What Is The Common Wire On A 3 Way Switch

How Does A 3-Way Switch System Work?

In a 3-way switching setup, three wires combine the two switches. The wires include two black traveler wires and a common wire.

When the power is turned on, any of the wires may be the hot wire depending on the configuration or how the switches are toggled.

The light switch is designed to interrupt the hot wire always.

Keeping this in mind, the white wire from the supply source always has an uninterrupted connection to the light fixture.

On the other hand, the bare grounding wires are connected to the grounding screws. Only the hot wire is routed through the switches that carry supply voltage.

How do I find the common wire on a 3-way switch?

If you look at any three-way switch, you won’t find any “On” or “Off” markings. This is because the toggle may turn on or off the light in both directions depending on the state of the other switch’s toggle.  

A more detailed description you’ll get to identify a 3-way switch is if you look at the switch itself and count the number of terminals it comes with. A 3-way switch has three screw terminals with a ground screw.

While the two of the terminals are light in color (usually copper-colored) known as the Travelers, the dark-colored screw is called the common terminal. On the other hand, the ground screw terminal is always colored green.

However, the chronology of these screw terminals differs based on different manufactures. If you buy two switches from two manufacturers, chances are their screw arrangement is different.

You’ll see that on some switches, both the traveler screws are placed on the same side of the body while the common screw is located on the other side.

Again, on some switches, the traveler screws are placed on opposite sides of the switch body while the common screw terminal is located on the opposite end of the body.

Wiring a 3-Way Switch

Okay, let us talk about how to wire a 3-way switch properly as you now know what is the common wire on a 3 way switch setup.

The right way of wiring a three-way switch depends on where the switch is connected in the circuit.

It is important to remember that 3-way switches always come in pairs.

Both the switches may come before or after the light within the circuitry.

It is also possible that there’s one switch on each side while the light fixture stays in the middle.

Step 1: Connect the Common Terminals

The first thing you need to do to wire a 3-way switch properly is to connect both the switch’s common terminal with the Hot Wire which is usually black in color.

The function of this hot wire is to carry power from the supply source and deliver it to the first switch and from there to the light fixture or load.

Depending on the circuit connection, the black or hot wire either will deliver power to the first switch or second switch before powering the load.

Or, the power may be transferred to the load and then to the second switch if the load falls in the middle.

Step 2: Connect the Traveler Terminals

The next step to wire a 3-way switch is to connect the traveler wires to the two traveler terminals of the switch body.

The traveler wires go through both two switches creating two potential pathways to complete the connection. The supply power can be transferred through any of the pathways to power up the load.

It doesn’t make any difference which wire goes to which switches as the traveler terminals are interchangeable.

So, it doesn’t matter whether you connect the terminals from the first switch to the second or the second to the first one.

Note: Terminal wires are also considered “Hot wires” as they carry electricity when any of the switches are turned on. To ensure safety, label the terminal wire with a band of black tape, especially if it is white which is usually considered as a neutral wire. It helps everyone understand that the wire isn’t a neutral wire.

3-way switch wiring schematic diagram
Figure: 3-way switch wiring schematic diagram

Step 2: Connect the Ground Wires

The other wires in a 3-way switch circuit are basically neutral and ground wires that are usually white and bare copper or green in color respectively. The neutral wire connects to the load directly bypassing the switches.

The ground wires connect the ground terminals on each of the switches and the load. You can see a 3-way switch wiring diagram power at the switch above which makes it easy to visualize how to wire a 3-way switch properly.


So, now you know what is the common wire on a 3 way switch circuit (which is none other than the hot wire mostly black in color).

I hope this article doesn’t only help you identify the common wire on a 3 way switch, but also lets you know how to install a 3-way switch with 2 wires.

I really wish that it helps you while wiring a 3-way switch next time.

Best of luck with the wiring. Thanks for reading up to this.