Adding a 3-way switch setup to a light fixture, and doing it yourself is a very inexpensive way to improve your home. With an easy to follow 3-way wiring diagram, changing from a single pole to a 3-way light switch allows you to turn a light on from multiple locations, such as at the top and bottom of a staircase or both ends of a hallway.
Fortunately, the process of How to wire a 3-way light switch is relatively simple.
- 3-way switches (2)
- 3-way wire (which has a black, white, and red wire -and of course a copper ground wire),
- electrical boxes of appropriate size to hold 3-way switch and wire
- wire cutters and strippers
- standard electrical tape
- a non-contact voltage tester
- 3-Way light switch wiring diagram – below.
Depending on the current setup and the fixture you’re wiring the switch into, you may also need some additional wire nuts to create secure connections to your home’s existing wiring.
For the instructions below, we’re assuming that you are converting an existing 2-way switch to a 3-way version by changing the current switch and adding a second one in another location nearby. However, the basic principles also apply to replace 3-way switches or installing them in new construction.
For all of you “Visual Learners” out there – and anyone else – we highly recommend you watch this short video on 3-way switch wiring:
Plans & Instructions – “How to Wire a 3-way Switch”
Step 1: Turn the Power Off at Your Breaker Box
The first step in any electrical project is to make sure there is no power going to the circuit you plan to be working on. Be sure to identify the electrical circuit correctly you’ll be wiring into, and turn off the breaker at your home’s main electrical panel. To make sure there’s no room for doubt, you can use a Non-contact voltage tester such as this best seller on Amazon, to check whether there is power being supplied to the wires at the existing switch you’ll be working on.
Have you Turned The Power Off to the Electrical Circuit you will be working on?
Step 2: Install the Correct Boxes
Before you can install your new three-way switch, you’ll need to put an electrical box in to accommodate it. Make sure the outlet box you choose is large enough, as 3-way switches usually require a bit of extra room due to their third wire. For the same reason, there’s a good chance you’ll have to change the box on the existing single pole switch to make room for the additional wiring. Once your boxes are in place, you can start the process of installing and wiring the switches themselves.
Step 3: Run (feed) New Cable (Romex) Between the Switches
Regardless of what 3-way switch wiring diagram, you’re following, you’ll need to use a 3-wire cable to connect the two 3-way light switches. So what you should see if you have correct 3-wire electrical cable (romex) is a black (power) white (neutral) and now a 3rd (Red) wire. This is the 3-wire cable which you must have to wire a 3-way light switch.
The exact cable you use depends on the gauge of the existing wiring in the rest of the circuit, but in most cases, the correct cable will be either 12-3 or 14-3.
Step 4: Connect the Switches (below)
A) At the existing single pole light switch (the switch which is currently connected to the circuit breaker) remove this existing switch from the box. You will be replacing it with a new 3-Way light switch. Wire nut the neutral (white) wires together – This is the existing White neutral wire coming into the box, and the New white neutral wire from the 3 wire romex you’re going to use to connect the other 3-way switch – you will install in a minute. This first step will eventually send power directly to the Light fixture.
B) Connect the Black (hot) wire (coming from the romex cable that leads to your circuit panel) to your New 3-way light switch (#1) – you will connect the hot wire to the hot terminal on the 3-way switch, which is usually Black and stands alone).
C) Now, connect the traveler (red & black) wires from the new 3- wire romex cable to the two traveler terminals at the top of 3-way switch #1 the first switch. Keep in mind that the traveler terminals for red & black wires, are universal and will work regardless of which one the traveler wire is connected to. Finally, attach the existing copper ground wire to the 3-way light switch #1.
D) Repeat this process with the other 3-way switch (#2) using the same 3-wire romex cable you just connected to switch #1. The only exception here is that the black wire coming from the Light fixture will now connect to the standalone hot terminal on switch #2 – this common black wire will send power to the light fixture from the circuit breaker.
E) Lastly, If your light fixture isn’t wired yet, connect the light fixture to the 2 wire romex (black and white wires only) which leads to your new 3-way light switch #2, and you should have completed your 3-way light switch circuit.
Note: If your 3-way light switch #2 is connected between the power supply and the light fixture, as is the most common case, the existing 2-wire (black and white) romex can still be used to connect 3-way switch #2, and the light fixture.
Note: Make sure all of your Ground connections are completed and securely fastened.
Optional: Wiring Multiple Lights on a 3-way switch
The steps above describe installing a 3-way switch and provide a 3-way switch diagram utilizing one light fixture.
If you intend to add multiple lights with a 3-way switch – Refer to the 3 way switch for multiple lights diagram below:
Step 5: Finish Your Work and Test
Now that you have wired the switches to each other and the light fixture, it’s time to do a bit of finish work and test the circuit. Before turning the power back on, wrap a piece of black electrical tape around the white wires if you used them as travelers. By convention, the white wire in a 3- wire cable is neutral, and it’s important to leave an indication that the wire is hot for yourself or anyone else who may someday need to work on the switches. The white wire that runs to the fixture should be marked in the same way to avoid any confusion.
Now you just have to screw the switches to the boxes, put the face plates on, and restore power to the circuit. Test the switches to be sure they work. If you have any trouble, be sure to turn the power back off before inspecting the connections or trying to troubleshoot.
Important Note About Your Safety:
Before you grab your toolbox and set out to wire a three-way switch, be sure to take proper safety precautions. This type of electrical work isn’t overly complicated, but any electrical work can be dangerous if you don’t know what you’re doing. Always be sure to work with the power turned off and to proceed with care and caution at each stage of an electrical project. If you aren’t sure you know how to proceed or aren’t comfortable doing the work safely, it would be a good idea to hire a professional electrician do this job instead.
Also, be sure to check the type of wiring in your home. These instructions are offered for installing switches using standard Copper wiring.
Some homes, however, do use aluminum wiring instead. If your house has aluminum wires, it’s generally best to hire a professional do your electrical work.
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References & Additional Reading