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How to wire a 3-way light switch

The steps and details of how to change a light switch for multi-location control.

December 7, 2021

Not to sound too type-A, but more control is almost always a good thing. And when it comes to larger rooms in your home, as well as those with multiple entrance/exit points, the ability to control the lights from more than one switch is incredibly convenient.

From entry ways and stairwells, to formal dining rooms or open floor-plan spaces, you likely already have 3-way light switches (maybe even 4-way) in your home. But if you are looking to add that functionality into a new space, or even just want to update an existing 3-way switch as part of a DIY renovation or room upgrade, you might have wondered how exactly to get the job done…or even been a little intimidated.

But not to worry!

Installing a 3-way switch isn’t very different from how to wire a light switch or outlet, and this post is here to help break down the how-to steps.

Before we start with tools and wires though, some might be wondering what exactly makes a switch 3-way. And it’s a good question. 3-way switches are used to control a light or fixture from two locations. They can come in handy in a lot of areas of a home, but one of their best and most common uses is to control lights over a staircase. Often a home has a switch at both the top and bottom of a flight of stairs so a person can turn the lights on before they head up (or down) to safely see where they are going, and then conveniently turn the light off from whichever floor they are now on. 

But how is it different than any other switch?

While there isn’t usually a visual difference once installed in the wall, most 3-way switches use 3 screw terminals – one common and two traveler terminals – in addition to its grounding screw. A single-pole switch (the most common type of switch found in homes which turns on a light or fixture from a single location) only uses two. 
The wiring of the third terminal enables the two 3-way switches sharing control of a single light to register the position of the other switch, which dictates whether it is to turn a light on or off. Without three terminals, a switch cannot be used in a 3-way installation.

When selecting the switch(es) you will use for this project, be sure to confirm they are usable in 3-way applications.

  • Screwdriver
  • Wire Cutter / Wire Stripper
  • Wire Connector / Wire Nut
  • Voltage Tester

As always, the first and most important step before doing any kind of electrical work is to confirm that the power is off. Especially when working on existing installations where a light fixture is controllable from multiple switches, we strongly recommend using a voltage tester to check all devices and wires.

*Note the steps below are generalized to apply to any adorne® or radiant® 3-way switch installation. Be sure to also carefully review any installation instructions provided with your device before proceeding.
  1. Turn off power for the existing switch at the circuit breaker. Also, give anyone else at home the head’s up that you’ve turned off the power to do electrical work. You want to make sure nobody flips that breaker back on while you’re working.
  2. Next, test the existing switch. Try flipping the switch itself as well as using a non-contact voltage tester. For your safety, no further action should be taken until you are positive all power to the switch has been turned off.
  3. Remove the existing switch’s wall plate and mounting screws, then gently pull the existing switch out from the wall box.
  4. Identify and label the connected wires on the existing switch: The Hot or Common Wire (usually black and connected to the black or dark screw terminal on the switch) and the two Traveler Wires (often one red wire and another black wire, each connected to the lighter brass screw terminals on the switch). Additionally, there is likely a Ground Wire (usually a bare, copper wire connected to a green screw). Note that on older devices, there might not be a Ground connection.
  5. Now disconnect the wires from the existing switch. You can often pull the wire off existing terminals or potentially release the wire using a small screwdriver; or just snip them with your Wire Cutter. If necessary, strip the wires using the guide on the back of your new device. For reference, the standard is typically to strip the wire to ¾ of an inch. 
  1. Then, using the provided installation instructions for your specific device and referencing your wire labels, connect the wires to the appropriate terminals on your new switch: Black Hot Wire / Common Wire to the dark terminal (might also be labeled on the device itself as Hot or Common Terminal); Traveler wires to the lighter terminals. Note that the location of the traveler terminals can vary. Additionally, it doesn’t matter which traveler wire goes to which terminal. Just make sure your connections are all secure by tightening your terminal screws slightly once the wires are attached. 
  2. Gently folding the wires as needed, fit the new switch back into the wall. Attached to the wall box with the included mounting screws and finish the installation by snapping the screwless wall plate into place. 
  3. With the power still off, repeat steps 2-7 for the second 3-way switch. 
  4. Once both switches are completely installed, turn power back on at the circuit breaker and test your switches. 
  5. Enjoy the convenience of multi-location control! 
Interested in adding 3-way control with less wiring?  

Consider the adorne® or radiant® smart light switches and dimmers with Netatmo. When paired with an installed Smart Switch or Tru-Universal Dimmer with Netatmo, the battery-operated Wireless Smart Switches or Dimmers with Netatmo allow you to add multi-location control by simply mounting the device to any wall or surface – no wiring necessary. 

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