How to Wire A 3-Way Light Switch (7-Step Guide)

Does the thought of trying to wire a 3-way switch seem intimidating?  

It can be complicated, but by following this guide it will help you be confident in your work.  

In this guide, you will learn:

  • Three different possible ways to wire a 3-way switch
  • How to test your 3-way switch to be sure it is working properly!
  • National Electrical Code rules when wiring any switch
  • And more!
how to wire a 3 way light switch

While it is a little more complex than just wiring up a regular single pole switch, it can be a simple task to wire a 3-way switch once you understand what wires you need and where they need to be hooked up.  

How you need to wire everything will depend on where your main power or line wires come in at, whether they come into a switch box or a light fixture box.

As a licensed electrician, I ask that if you are uncomfortable or run into problems at any time while installing 3-way switch wiring, please stop and call a local electrician to come and finish the job. Keep reading to learn the 7-steps on how to wire a 3-way switch!

What You Need To Know When Wiring A Three Way Switch?

Anytime you use a 3-way switch, you will always have a pair of them.  This allows you to control one or more lights from two different locations in your house.  When getting ready to wire, be sure you have the proper wire for your job! 

It is very important that before beginning that you verify that there is no power on the wires you will be working with.  Electrical shocks can be very dangerous, and safety needs to be a priority! Most jurisdictions also require you to get an electrical permit to install new 3-way switch wiring, which will come with a small fee.

Two Styles of Wire

Homes are typically wired with NM cable; this refers to the non-metallic outer jacket surrounding the individual wires.  NM comes in many different styles, but for this job you only need to be familiar with two of them: the 2-conductor and the 3-conductor.  

Most likely you will run into either 14 or 12 gauge wire, and 'in the trade' the cables are known as follows: 

  • NM 14/2 - 14 gauge wire with a white outer jacket enclosing 2 current carrying conductors and a ground
  • NM 14/3 - 14 gauge wire with a white outer jacket enclosing 3 current carrying conductors and a ground
  • NM 12/2 - 12 gauge wire with a yellow outer jacket enclosing 2 current carrying conductors and a ground 
  • NM 12/3 - 12 gauge wire with a yellow outer jacket enclosing 3 current carrying conductors    

For this guide we are going to assume you will be working with 14-gauge wire, though it is possible to have 12 gauge wire. 

3-Way Switch Wiring Methods

There is a couple of methods to get line power to your lights.  One is by bringing the power into your switch box and the other is by having the power go to the light first. Both ways are used frequently; each creates unique ways on how the wires are run to the switches. 

Anatomy of a 3-Way Switch

There are 4 screws on a 3-way switch:

  • A dark colored screw - This is the common screw; the wires carrying power to the switch or to a light get landed on this screw. 
  • Two lighter brass-colored screws - These are the traveler screws; the traveler wires run in-between the two switches and MUST land on these screws.
  • A green screw - This is the ground screw, the bare copper ground wire will land here.

Using Pigtails 

When wiring up your switches you will need to create what is called a pigtail

This is a piece of wire about 6 inches long that will wire to the switch and then be tied in with other wires using a wire nut.  The National Electrical Code requires devices to be wired so that if one has to be removed, it doesn't disrupt anymore down stream.  The use of pigtails makes this possible.

Choosing Wire Nuts 

Wire nuts are NOT a one size fits all.  You need to have the correct size for the amount and gauge of wires that you will be using.  For around the house projects it is good to have a few yellow and red wire nuts on hand.

Read Also >> How To Wire A 220-Volt Plug With 3 Wires?

Supplies You'll Need To For 3-Way Switch Wiring

  • Voltage Meter - A voltage meter allows you to verify the power is off 
  • Screwdriver - A screwdriver will be used to make the wire terminations and install the cover of the outlet
  • Wire Strippers - Wire strippers are used to strip the insulation off the individual wires
  • Utility Knife - A utility knife will be used to remove the outer jacket to expose the individual wires 
  • Electrical Tape - Electrical tape will be used to wrap the outlet around the termination screws as another layer of safety  
  • Needle-nosed Pliers (Optional) - Needle-nosed pliers can be used to make the hooks on the end of wires 
  • Wire Nuts - Wire nuts are used to tie wires together
  • Extra Wire - Extra wire is good for making pigtails 

How To Wire A 3-Way Light Switch (7-Step Guide)

  1. Identify Your Amperage and Wire Gauge 
  2. Verify There is No Power
  3. Strip the Outer Cable Jacket
  4.  Strip the Ends of the Individual Wires
  5. Terminate The Wires
  6. Double Check Connections and Install Switch and Cover
  7. Test Your Switch

Step 1 - Identify Your Amperage and Wire Gauge 

Identify the amperage and wire gauge required for your circuit.  

The amperage will determine what wire gauge or thickness of wire you will need.  It is important that this is sized properly so that it can handle the amount of current or amperage running through the wire.  There is 2 typical household wires sizes:

  • 14-Gauge wire is suitable for 15 amp breaker
  • 12-Gauge wire is suitable for 20amp breaker

You can use wire that is rated higher than the amperage rating of the circuit breaker, but you CANNOT use wire that is rated lower! 

It is important to continue using the same gauge wire throughout the entire circuit!

Below is a simple 3-way switch diagram...

Step 2 - Verify There is No Power

Verify there is no power on the wire you are hooking up by using your voltage tester.

Carefully use one probe to touch the end of a hot wire while touching the other probe to a ground wire; your meter should read zero volts.

Step 3 - Strip the Outer Cable Jacket

Strip the outer cable jacket by using the utility knife to gently slice through the outer insulation. 

Be careful while doing this to ensure you don't cut too deep and damage the insulation on the individual wires.  

The National Electrical Code requires there to be 6-inches of free conductor from the point that it enters the box, and the wire must extend 3-inches past the edge of the box. So you will need to strip a minimum of 6-inches of the outer jacket off.  

Read Also >> How To Convert Watts To Amps?

Step 4 - Strip the Ends of the Individual Wires 

Strip the ends of the individual wires so you can wire them.

Some will be terminated at the screw of the switch, others will just be wire nutted together.  This will determine how much insulation will need to be stripped off. 

If the wire is being terminated at a screw, you will strip off approximately 1-inch of insulation so you can create a hook on the end of the wire.  Take the tip of your strippers or a pair of needle-nosed pliers and pinch the end of the wire and curl it around so the end of the wire can hook over the screw.

If the wire is going to be wire nutted with other wires, you will need to strip off about 1/2 in to 3/4 in.  Try and strip off the same amount from each wire.  This will make it easier to put the wire nut on without the bare wire sticking out from below the wire nut. 

Step 5 - Terminate The Wires 

Terminate the wires on to the switch. If your line or main power is coming into a switch box:

Switch #1 Power Coming In

  • The black of the 14/2 line wire will hook to the dark common screw.
  • The white neutral out of this 14/2 will be wire nutted to the white neutral of the 14/3 that runs between the two switches. 
  • The ground from the 14/2 and the 14/3 will be wire nutted together with a pigtail.  The pigtail will then terminate at the green screw of the switch. 

Switch #2 Power Going Out to the Light

  • The black of the 14/2 coming from the light will hook to the dark common screw.  
  • The white neutral out of this 14/2 will be wire nutted to the white neutral of the 14/3 that runs between the two switches.
  • The ground from the 14/2 and the 14/3 will be wire nutted together with a pigtail.  The pigtail will then terminate at the green screw of the switch. 

If your main power comes into the light fixture then from one switch to the next:

In this scenario it will require you to run a NM 14/4 between the two switches.  This j gives you 4 current carrying conductors along with a ground.  The National Electrical Code requires a neutral at almost every switch.  Even if it has nowhere to terminate.  

 Light Fixture Power going out to Switch #1 

  • The black of the 14/2 line wire will wire nut to the black of the 14/2 going to the first light switch 
  • The white neutral of the line 14/2 will wire nut to the 14/3 neutral and a pigtail.  The pigtail will then hook to the silver screw of the light fixture.  
  • The red of the 14/3 will hook directly to the brass screw of the light fixture and then it will hook to the common or dark screw of the switch.  
  • The ground from both 14/2 and 14/3 will be wire nutted together with a pigtail.  The pigtail will then terminate on the green screw of the light fixture.

Switch #1 to Switch #2

  • In the box for switch #1 the blacks from the 14/3 and 14/4 will get tied together via a wire nut. The same will happen with the whites.
  • The red and the blue from the 14/4 will be your travelers, and they will land on the lighter brass-colored screws of the switch.  
  • The ground from the 14/3 and 14/4 will be tied together with a pigtail and the pigtail will terminate on the green screw of the switch.

Switch #2 Box

  • The black of the 14/4 will terminate on the darker common screw. 
  • The red and the blue will land on the travelers, lighter brass-colored screws. 
  • The ground will terminate on the green screw
  • The white will just get a wire nut put on the end of it and tucked into the box.  

If your main power comes in to the light fixture and then to each switch separately. This scenario also requires you to run an NM 14/4 wire.

Below is another simple 3-way switch wiring schematic...

Light Fixture Box

  • The black from 14/2 line power cable and the black from Switch #1 will get wire nutted together
  • The neutral wires from the 14/2 and both 14/4s will get tied together along with a pigtail.  The pigtail will terminate to the silver screw of the light fixture 
  • The reds from each of the 14/4 will get wired nutted together and the same for the blues. 
  • The black from the 14/4 that goes to Switch #2 will get terminated straight to the brass screw of the light fixture. 
  • The grounds from all 3 wires will get combined along with a pigtail under a wire nut.  The pigtail will terminate on the ground screw of  the light fixture. 

Switch #1 Box

  • The black will terminate on the common screw 
  • The blue and the red will terminate on the traveler screws 
  • The ground will terminate on the ground screw of the switch. 
  • The white wire will not terminate anywhere, it will just get a wire nut on the end and tucked into the box. 

The wires in switch box #2 will terminate the same way as the wires in switch box #1.

how to wire a 3-way light switch

Step 6 - Double Check Connections and Install Switch and Cover

Double check that you have the screws all tightened down on the wire firmly. 

If everything looks good take and wrap electrical tape around the body of the switch covering the screws and any bare wire.  This provides protection from someone receiving a shock or the wires touching and shorting out.  

Once you are satisfied, you can carefully fold the wires into the box, mount the switch, and put the switch plate on.  Once the cover is securely in place, you can turn your power back on.

Read Also >> How To Install & Wire Island Range Hoods?

Step 7 - Test Your Switch

Test your switch by alternating between each switch being turned on and off.  It is best to have another person help you that way you don't have to run back and forth to the switch. 

To do this you will flip your switch and then the other person with flip their switch and you will do this 3 times, alternating back.  This verifies all the power configurations that the switch is able to do.  If the light turns on and off as it is supposed to you are done and everything is wired correctly. 

If a switch doesn't turn the light on or off, you have your 3-way switch wiring wrong and need to go back and double check the wiring.

Read Also >> How To Wire A 220-Volt Plug With 3 Wires?

Frequently Asked Questions

What Is The Point Of A 3-Way Light Switch?

The point of a 3-way light switch is to provide two light switch locations for a single light fixture. The most common three-way switch is for interior stairways so that the stairs can be lighted for safety reasons from the top or bottom. 3-way light switches are also common in bedrooms, foyers, or living rooms where there are at least two entrances to a single room. Some cities or counties may require 3-way switches to be installed if there are 6 or more risers on the stairway.

How Should A 3-Way Switch Be Wired?

A 3-way switch wiring should be installed using 3 wires.  Two of the wires should be black and red, called the travelers; these will be landed on the lighter brass-colored screws.  There will be another black wire, this is the common, and will land on the single darker screw.  The last wire will be a bare ground wire landed on the green screw.  

What Color Wire Goes To The Black Screw On a 3-Way Switch?

The black screw known as the common, the black wire that comes from the 14/2 is landed on this screw.  This is either carrying line power to the circuit, or it is carrying power to the light from the switch.

What Are The Different Parts Of a 3-Way Light Switch?

There is 3 screws on the body of a 3-way switch, along with the green or ground screw.  

One screw will be a darker color, this is known as the common screw.  There will be two other screws that are lighter brass colored; these are known as the travelers.

How Do You Wire a Leviton 3-Way Light Switch?

A 3-way light switch is wired using 2 travelers from a NM 14/3 cable usually black and red in color.  The 3rd wire, usually another black from a NM 14/2 cable or a white wire marked with black tape, will land on the darker colored single screw called the common.  The ground wire will land on the green screw. 

Final Thoughts On Wiring A 3-Way Switch 

Safety is the most important thing, so make sure you have the power turned off before you begin your work.  Take the time to look over what you have to ensure you have the right gauge wire and understand where each wire is coming from and where it is going.  This will help ensure you get the 3-way switch wired  correctly.

If you have any doubts, questions, or are no longer feeling comfortable about working on it, be sure to give your local electrician a call to come and give you a hand! 

I hope you enjoyed this Home Inspector Secrets guide!

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