How to Wire 3 Ways ( Free Course): A Beginner’s Guide from a Journeyman Electrician
If you’re an electrician, DIYer, or homeowner looking for training on how to wire a three-way switch, you’ve come to the right place. I’m sharing this information from the perspective of a journeyman electrician. However, please note this is for learning purposes only—I never recommend doing your own electrical work unless you’re qualified and understand all safety precautions.
Stick around for the entire post because, at the end, I’ll walk you through three different ways to wire a three-way switch, which is pretty interesting.
What is a Three-Way Switch?
A three-way switch, sometimes also called a two-way switch, is designed to control a light or set of lights from two different locations. For example, this setup is common at the top and bottom of staircases or at either end of a hallway.
Why the two names? They’re often called two-ways because you can only use two switches of this type in a circuit to make it work properly.
How Does a Three-Way Switch Work?
The key feature that identifies a three-way switch is that it has three screws (excluding the ground screw). These screws consist of one common terminal and two traveler terminals.
- The common terminal is usually black.
- The two traveler terminals are typically brass or copper colored.
- The ground screw is green and should only be connected to the ground wire—not any live wire.
The Basic Wiring Setup
In this example, we have the power feed coming from the power source, which you can imagine being plugged in to show the live current. We start with the first three-way switch, the second three-way switch, and then the light fixture itself.
Note: In the background, you might see extra boxes for a four-way switch setup, which will be covered in a future tutorial.
Wire Gauge and Device Ratings
The wiring used is typically 14/2 or sometimes 12/2 gauge wire, suitable for 15-amp rated devices.
Step 1: Connect the Grounds
Ground wires are connected first inside metal boxes (commonly used in older installations). The ground wires are twisted together and secured at the back of the box. This is crucial for safety.
Step 2: Neutral Wire to the Light
For the circuit to work, the light fixture must have a neutral connection. The neutral wire is usually white. No matter how you wire a three-way switch, the neutral must always go directly to the light fixture.
Step 3: Wiring the Neutral Through the Switch Boxes
From the power feed, run the neutral wire through the first switch box, twist it together with the neutral wire going to the light, and continue the neutral wire through to the second switch box.
This “process of elimination” method is very important and helps avoid confusion in complex circuits with multiple switches.
Step 4: Wiring the Travelers and Commons
Each three-way switch box will have:
- One black wire (the common)
- Two traveler wires (usually red and black)
The black wire on the power feed side goes to the common terminal on the first switch. The two traveler wires connect to the traveler terminals.
At the other end (second switch), the common terminal connects to the black wire going to the light fixture.
How the Switch Works
When you flip either switch, it sends power through one of the traveler wires, changing the path of electricity. This toggles the light ON or OFF depending on which traveler wire is energized. The common terminal is always connected but switching flips the current path between the two traveler terminals.
Summary
- Three-way switches allow control of lights from two locations.
- They have one common terminal and two travelers.
- The power feed common black wire connects to the first switch’s common terminal.
- The light fixture neutral must always be connected directly.
- The two traveler wires run between the switches.
- Flipping either switch changes which traveler is energized, turning the light on or off.
Wiring a three-way switch can seem confusing at first, but once you understand the roles of the common and traveler wires and the importance of the neutral connection, it becomes much easier.
First Method: Power Feed Into the First Three-Way Switch
This is the classic method where power comes into the first three-way switch, travels through the travelers to the second switch, and then to the light fixture.
- The black wire on the first switch is the common wire going out to the light fixture.
- Travelers run between the two switches on red and white wires.
- Grounds are connected properly, especially if using metal boxes.
- When wired correctly, flipping either switch turns the light on or off regardless of the other switch’s position.
If the switches don’t work properly (for example, if flipping one switch doesn’t control the light), the most common cause is that the travelers or common wires were mixed up during installation. Make sure the common wires are connected to the black screws on the switches.
Second Method: Power Feed Into the Second Three-Way Switch (Three-Way Tail)
This method is handy for rewiring or situations where running wires to one box is difficult.
- Power feed is moved to the second three-way switch instead of the first.
- A three-wire cable runs between the two switches (called a “three-way tail”).
- The neutral wire is run directly to the light fixture.
- The black common wire is connected to the power feed on the second switch, then the red and white travelers run back to the first switch.
- Black common terminals are always used for commons; red and white are travelers.
This method is helpful in retrofit situations or tight wiring conditions and works exactly like the first method from the user’s perspective.
Third Method: Power Feed Into the Light Fixture
Common in rewiring projects where it’s difficult to pull wires through walls.
- Power feed is connected directly to the light fixture.
- Two-wire cable runs from the light to the first three-way switch.
- Three-wire cable runs from the first to the second three-way switch.
- The white wire is used as a “switch loop” — it is marked as hot (powered).
- Commons on switches are always black.
- Travelers are red and white.
- The neutral goes directly to the light fixture’s silver screw.
This method allows a continuous wiring system from the power source through lights and switches without extra wires in multiple boxes. It is simpler for rewires but less common in new construction.
Important Tips and Modern Considerations
- Always mark your wires to keep track of travelers, commons, and neutrals—especially in multi-gang boxes.
- Black wires should always be used for commons on three-way switches. Using white wires as commons is bad practice and causes confusion.
- Neutral wires are critical now due to the rise of smart switches requiring neutral in the switch box.
- New codes increasingly require neutrals in all switch boxes. This is a challenge because some wiring methods don’t provide neutrals in the switch boxes.
- Manufacturers are working on new cable options (such as four-wire cables) to help with this, but they are not yet widely available.
- Because of this, the first method (power feed into the first switch) is becoming the most practical and compliant method for installing smart switches today.
Final Notes
These are the three main wiring methods you’ll encounter. There are a few more obscure ways to run power, but these cover the vast majority of installations and code requirements in North America.
If you want to learn about wiring four-way switches, check out our upcoming video covering that topic in detail.
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