If you have lights in your home that can be controlled by two different light switches (rather than just one), those lights are usually called three-way lights and the switches are called three-way light switches. If you know anything about circuits, you at least know that the on/off switch is probably the simplest circuit. However, things can get a bit complicated if you add a second switch to control the same object.
How a light switch works?
Before explaining how a three-way light switch works, it’s important to know how a regular light switch works. These are called unipolar light switches and allow you to turn a light fixture on or off from a single position. This is the most common type of light switch and is mostly found in bedrooms, bathrooms, and other simple room layouts where only one light switch is really needed.
In the diagram below, the neutral return wire and ground wire are not shown to make the diagram as easy to understand as possible. If this concerns you, just know that the neutral “return” wire in the circuit is not connected to any switch and remains connected, while the ground wire is connected to the green screw on all switches.
In a traditional wiring setup with a single light fixture and a single switch, there is a hot wire coming from the electrical panel that powers the light fixture. However, a light switch is installed to match the heating element. So when the light switch is turned off, the heating element is disconnected and the light is not powered. When you flip the switch, the heating wire reconnects and powers the fixture.
How does a three-way light switch work?
If you look at a three-way switch, you will see that it has four terminal screws. There are two traveler terminals, usually identified as light colored bronze or copper, the ground terminal green, and the common terminal often dark colored.
A three-way switch does not have an on/off designation found on standard switches. This is because you can toggle either position on or off. Within a switch, one of the traveler terminals is connected to a common terminal and can create or break a circuit depending on whether the other switch traveler terminals match or not. It’s like an intensive game where you flip two cards over and try to match them.
The light turns on when the two individual two-way switches match the traveler wire, and turns off when they do not. It can match both red or both black, but not black/red or red/black.
The two traveler terminals may be on the same side of the switch or on opposite sides of the switch, depending on the switch manufacturer.
What does a three-way switch do?
Like two-way switches, three-way switches turn lights on or off. However, there is a crucial difference. The three-way switch is used in conjunction with other three-way switches. Each of them has the power to disrupt the flow of electricity and turn off lights in different parts of the room.
If you want to be able to turn lights on or off from multiple points in the same room, both switches should be three-way switches. This gives both people the opportunity to stop the flow or restart the flow of electricity.
The three-way switch connects to wires that connect to the heat and lights in the electrical panel. However, they have two special wires that connect to each other called travellers.
These two wires create their own internal circuit so that when the light is off, either switch can turn it on. If the light is on, you can turn it off with one of the switches. This type of switch is most commonly used in hallways or large rooms that have more than one way to enter.
Can a 3-way switch be used as a regular switch?
Yes. Use either the common terminal or the traveler terminal as the incoming or outgoing power source, leaving the other traveler terminal empty. This is an unnecessarily expensive setup, but I don’t mind if it’s worth the extra money.
What is the difference between a 2-way light switch and a 3-way light switch?
The main difference between a two-way switch and a three-way switch is the number of positions that can control the circuit. A two-way switch allows control from two positions, and a three-way switch allows control from three positions.
How does electricity flow in a 3-way switch?
The black hot wire goes into the left switch. A three-way wire including a red, black, and white wire runs from the left switch to the right switch, with the white wire carrying ground and the red and black wire carrying the output of the left switch terminal.
Why do you need a 3-way light switch?
A three-way switch is typically used to control one lighting fixture from two different positions. For example, at each end of a long hallway or staircase, a three-way switch could be used so that a light turns on when you approach one end of the hall or staircase and turns it off at the other end.