Single-pole wall switches are used in circuit configurations where a light (or group of lights) is controlled from a single wall location. Single-pole switches can also control appliances or electronics. For example, a single-pole switch may be used to control power to an outlet that powers a floor lamp, stereo, or video system.
Single-pole switches are by far the most common type of switch in a home, and because they get lots of use, sooner or later it's likely one will fail. Replacing a standard single-pole switch is among the easiest of all home wiring repair projects. But all electrical repairs come with some risk of shock, so it's important to have some basic understanding of wiring circuits in order to perform this repair.
Before You Begin
A wall switch is a device that controls the flow of current through the live "hot" wire of an electrical circuit. When in the open (OFF) position, the switch stops the flow of current from the source to the light fixture or other device. When switched to the closed (ON) position, the switch restores the flow of current through the entire circuit, allowing the light fixture to illuminate or the appliance to run. Thus, a wall switch is always connected to hot circuit wires, and it usually does not have a neutral connection at all.
There are several different types of switches that can be used in different configurations, For example, three-way switches are used when you want to control a light fixture from two different wall locations, while a four-way switch is used in conjunction with three-way switches when you want to control lights (or another device) from three or more locations. But most wall switches in your home are the single-pole type, where a switch controls a light (or group of lights) or an appliance (a garbage disposer, for example) from a single wall location.
When you examine a single-pole switch visually, you will see a pair of screw terminals along the side of the switch, each one attached to a hot wire—one arriving at the switch location from the source (upstream), the other leading onward to the light fixture or appliance, located downstream in the circuit. The appearance of the wiring inside the electrical box may vary depending on the circuit configuration and age of the wiring system, but the important thing to remember is that the wires connected to the side of the switch are both hot wires. In the case of a single-pole switch, these wires are interchangeable—it doesn't make any difference which wire is attached to which screw terminal.
Inside the switch is a metal pathway that closes when the switch is the ON position, and opens to interrupts the flow of power when the switch is turned OFF. Eventually, that pathway or the springs that operate the pathway wear out, at which point you'll need to replace the switch.
In addition to the hot wire connections, new single-pole switches also have a green grounding screw that must be connected to the circuit's grounding system. Older single-pole switches may not have this grounding screw, but when you replace such a switch, it's important to establish this grounding connection on the new switch. How you do this may vary, depending on how your home's circuits are grounded. Usually, it's a simple matter of pigtailing the switch's grounding screw to the circuit grounding wires.
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Equipment / Tools
- Non-contact voltage tester
- Wire strippers (as needed)
- Needle-nose pliers (as needed)
- Standard single-pole light switch
- Grounding pigtail wire (if needed)
- Wire connector (if needed)
Turn off the Power
Turn off the power to the switch circuit by switching off the circuit breaker in your home's service panel (breaker box). If your panel has fuses instead of breakers, unscrew the appropriate fuse and remove it from the panel.
Be careful about trusting the labels or circuit index inside your electrical panel. It's very common for circuit labels to be incorrect, so always check for power after shutting off a circuit.
Test for Power
Remove the two screws on the switch cover plate, and carefully remove the cover plate. Use a non-contact voltage tester to test all of the wires in the switch box to confirm the power is off. Also, touch each of the switch's side screw terminals with the tester probe. If the tester lights up at any time, indicating the presence of voltage, return to the service panel and shut off the correct breaker; then retest the wires to confirm the power is off.
Remove the Old Switch
Remove the two screws that hold the switch to the box. Carefully pull the switch from the box, and check it once more to be sure the power is off to the circuit feeding the switch.
If your switch is a dimmable type, it will have a much different appearance. Dimmer switches have larger bodies, and they are generally connected to the circuit with wire leads and connectors rather than screw terminals. If you are replacing a dimmer-type switch, make sure to buy the proper replacement.
Inspect and Disconnect the Switch Wiring
Note the switch wiring. There should be one wire only under each screw terminal. One of these will likely be black, it is the feed wire from the power source. The other may be black, red, or white, depending on how the age of the system and the location of the switch on the circuit, but it always serves as a hot wire in a switch configuration. The switch terminals are interchangeable, so there is no need to identify which is which.
If there is a white wire connected to the switch, you are probably looking at a switch loop configuration, where the switch is the last device in the electrical circuit. In this instance, the white wire is being used as a hot wire, and it should be labeled as such with a tab of black or red electrical tape. If it doesn't, you can add this tab during the replacement.
If there are other white wires in the box that are not connected to the switch, these are neutral circuit wires that are simply passing through the box; they should be left as is.
Loosen each screw terminal and remove the circuit wire. If your switch is connected via push-in wire connectors on the back of the switch, you can release the wires by pushing a small nail or screwdriver into the release slot next to the push-in connection. Push-in connections are regarded as inferior by electricians, and it's best to use the screw terminal connections when you install the new switch.
Some "smart" switches, which can be controlled by smartphones and other wireless devices, require a neutral wire to maintain a wireless connection. Install these according to the manufacturer's directions.
Connect the New Single-Pole Switch
Connect the green grounding screw on the switch to the circuit's bare copper grounding wires. If the circuit has just a single grounding wire, then it can be attached directly to the switch's grounding screw. If there are two grounding wires, then attach a grounding pigtail to the switch's grounding screw and join the pigtail to the circuit grounding wires with a wire connector. Pigtailing is also the method used to connect a metal electrical box to circuit grounding wires—a box pigtail isn't necessary with a plastic electrical box.
Inspect the end of each hot circuit wire. It should have about 1/2 to 3/4 inch of bare wire at the end and should be formed into a hook-like loop. If the wire end is in poor condition, trim off the bare end; then strip about 3/4 inch of insulation, using wire strippers. Bend the end of each wire into a C-shaped loop and wrap it around a screw terminal on the switch in a clockwise direction. Tighten the screws down firmly.
Tug on all connections to make sure they are tight.
Complete the Job
Gently tuck the wires into the electrical box, then mount the switch to the box with its two mounting screws. Reinstall the switch cover plate. Restore power to the circuit by switching on the circuit breaker (or reinstalling the fuse). Test the switch for proper operation.