In this guide, you will learn How to wire a 3-way light switch and connect (two) 3-way switches to an existing or a new light fixture is a DIY project most homeowners can do on their own.
In addition, when you learn how to wire a 3-way switch and make connections to multiple lights – you will save significant costs of electrician fees, and make a significant improvement to your home.
Ok, No more fumbling in the dark. This easy-to-follow 3-way wiring diagram – changing from a single-pole to a 3-way light switch, will allow you to turn on a 3-way light anywhere in your house.
How to Wire a 3-way light switch
Learning to wire a 3-way light switch involves more than simple electrical projects – like installing an electrical box for an Electric Fireplace.
However, the task is simple enough. Get started by assembling these materials, then move on to Step 1 to begin installing a 3-way light switch:
A) Purchase Electrical Supplies:
- 3-way switch (2)
- 3-way wire (which has black, white, and red (coated) wires – and of course, a copper ground wire),
- electrical boxes of the 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 – See 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 single switch and adding a second one in another location nearby.
However, the basic principles also apply to replacing existing 3-way switches or if you are installing them in new residential construction.
B) Follow a 3-Way Switch Diagram.
To understand the basic circuit requirements of installing a 3-way switch, follow this basic 3-way light switch diagram:
Installing a 3-Way Light Switch:
Step 1: Turn the Power Off at Circuit Breaker
Confirm the power source is off, and ensure no electrical power is going to the circuit you plan to work 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 ensure there’s no doubt, you can use a Non-contact voltage tester, such as a Voltage tester, to check whether power is supplied to the wires at the existing switch you’ll be working on.
Ok – Have you Turned The Power Off to the Circuit Breaker you will be working on yet? If so, move on to step 2 below:
Step 2: Install the Correct Electrical Boxes
Before installing your new three-way switch, you will install an electrical box to accommodate it. Ensure the outlet box you choose is large enough, as 3-way switches usually require a bit of extra room due to the third wire in the electrical outlet box.
For that same reason, there’s a good chance you’ll have to remove and change the existing single-pole switch box to a larger outlet box to make room for the additional wiring.
Once your boxes are in place, you can start installing and wiring the switches. Refer to the above 3-way switch diagram.
Step 3: Run New Cable (Romex) Between the 3- Way 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 the correct 3-wire electrical cable (Romex) is a black (power), white (neutral), and now a 3rd (Red) wire.
This wire configuration is the 3-wire cable required 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: Make The Connections for 3-Way Switches (See 3-way switch diagram above)
- A) Remove this existing switch from the box at the single pole light switch (the switch currently connected to the circuit breaker). 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 will use to connect the other 3-way switch – you will install it 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) Connect the traveler (red & black) wires from the new 3-wire Romex cable to the two traveler screw terminals at the top of 3-way switch #1, the first switch. Remember 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 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 most common, the existing 2-wire (black and white) Romex can still connect a 3-way switch #2, and the light fixture.
Make sure all of your Ground connections are completed and securely fastened.
Step 5: Finish and Test Your Work.
Now that you have wired the switches to each other and the light fixture, it’s time to do some 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.
Traditionally, the white wire in a 3-wire romex cable is neutral, and it’s essential to remember that the white wire is hot if you grab onto it.
Final Step: Test Both 3-Way Switches
Now you just have to screw the light switches to the outlet boxes, put the faceplates on, and restore power to the circuit.
Test the switches to be sure they work. If you have trouble, turn the power off before inspecting the wiring connections or troubleshooting.
First, turn the power off to troubleshoot the 3-way switch light switch. Then, trace your way back to each wiring connection and confirm all wires are correctly connected and that all the wire connectors and screw terminals are tight.
Once you have completed this step, your 3-way light switch wiring should be completed.
For all of you “Visual Learners” out there – and anyone else – we recommend watching this short Video, How to wire a 3-way switch:
Wiring “Multiple Lights” on 3-way switches
The steps above describe installing 3-way switches and include a 3-way switch diagram utilizing one light fixture.
If you intend to add multiple lights with a 3-way switch – Consult the 3-way switch diagram for multiple lights below:
Important Note About Your Safety:
Before you grab your toolbox and wire a three-way switch, a ceiling fan, or any other electrical work, 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 to do this job instead.
Some homes, however, do use aluminum wiring instead. If your house has aluminum wires, hiring a professional to do your electrical work is generally best.
Frequently Asked Questions: (FAQ)
Q: What Color is the Hot Wire in a 3-Way Light Switch?
A: The Hot Wire (sometimes referred to as the “Common Wire” or the “Line Wire) will be the “Black Wire” when wiring a 3-way Light Switch.
Q: What Color Terminals Receive What Color Wires in a 3-Way Switch?
A: Black or Red Hot Wires attach to Brass Colored Terminal Screws or Black wire leads. White wires connect to Silver Colored Terminals or White color leads.
Q: How Do You Know Which Black Wire Is Hot In a 3-Way Switch?
A: The safest way to determine which of the two Black Wires is Hot is to use a Circuit Tester or a Multi-meter. Test each wire one at a time until you get a reading on your multimeter.
Q: Are two 3-way Switches required to Control One Light?
A: 3-Way Wiring does require two 3-way Switches to Control one light. Typically, the two different light switches are installed on the opposite side of a corridor and the top and bottom of a flight of stairs.
We hope this guide has helped us wire a 3-way light switch. Please remember that electrical wiring in a home is no joke and can lead to serious harm if done incorrectly.
If you are unsure about this electrical project, consult or hire a licensed electrician first.
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