How Light Switches Work

If your light switches are starting to look a little worn, or you're in the process of upgrading to a smart home system, then it may be time to consider replacement. There are a variety of styles and types of light switch available, but understanding how each works can help you choose the best one for your situation.

Light switches don't store power, but rather act as gatekeepers for electricity traveling through your wiring network. When a switch is flipped to the ON position, a spring-loaded metal gate snaps closed and completes the circuit leading to your fixture. When the switch is flipped to the OFF position, the gate opens and interrupts the flow of electricity.

While there are many different types of light switch available, they all serve similar functions. Most switches have three screw terminals, a dark-colored screw called the common, a lighter-colored screw labeled "traveler," and a green grounding screw. There are two possible ways to wire a switch depending on its configuration, but regardless of the type, the electrical connections must be made properly to prevent fires or injuries.

When working with a switch, it is important to turn off the power at your breaker box or fuse panel before beginning any electrical work. This will protect you from injury or even death should an electric shock occur while you are working on a light switch. Likewise, when you are installing a new switch or replacing an existing one, always start with the power turned off and use a voltage tester to verify that no live current is present.

In most residential settings, single-pole switches are the most common. These are the basic toggle or rocker switches that you can find in homes built over the last century. While they are simple to install, the wiring behind them can be quite complicated and dangerous to work with if not handled correctly.

With a single-pole switch, you'll typically see an incoming hot wire (black or any other color except green), a return wire leading onward to the light fixture, and a circuit ground wire that is either bare copper or green with black tape over it. There are also two traveler wires, which are linked to the open arms of a V-shaped mechanical configuration inside the switch.

For those who are looking to upgrade their lighting systems and make them compatible with smart home devices, a double or triple light switch is the way to go. Available in both rocker and toggle formats, these switches allow you to control a single light from multiple locations throughout a room or hallway. To operate a double or triple switch, each must be connected to a separate common wire (black or any other color) and then have its own pair of traveler wires that are connected to the open legs of the V-shaped configuration. Then, when the switches are flipped to the ON position, the runner terminals on each of the switches will line up internally and complete the circuit, and the light is turned ON.