How to Identify Wires in a 3-Way Switch?

3-way switch


The 3-way switch is one of the most common switches to control various light fixtures, especially ceiling lighting. With this switch, you can control lighting from two different locations. For instance, you can turn on the light from one end of a long hallway then switch it off at the other end. This way, you will not need to go where you initially switched on the light to turn it off.

If you want to enjoy this benefit of a 3-way switch, then your first step is to learn how to identify wires in such a switch

How Can I Tell Which Wire Is Common on a 3-Way Switch?

The 3-way switch has three electrically active terminals, and one of them is the common terminal. This terminal acts as the “bridge” between the load—a light fixture—and the power supply. It means the wire connected to the common terminal leads to a load of a hot wire from the mainboard

You can identify the common terminal as a single dark-colored screw. Meanwhile, the green color is the ground screw. While the color and arrangement of the screws may depend on the switch manufacturer, most 3-way switches have such colors. 

Moreover, some 3-way switches have the common screw isolated on the other side of the switch body while the two traveler screws are on the opposite side.

Which Wire Is Neutral on a 3-Way Switch?

The neutral on a 3-way switch is the white wire. Or you can use a multimeter to identify a neutral wireThe job of a neutral wire is to return the power to the energy source to complete the electrical circuit. The neutral wire is essential in any electrical system because it completes the cycle of such a system.

Without it, there would be no circuit as a neutral wire is necessary to come back to the power source after flowing along with the electricity. You can also add a neutral wire for a smart switch

How Do I Identify a Switch Wire?

To understand the switch wire, you must also understand what Live wire is. The wire that brings the live supply to the switch is the Live wire having a black color. When the switch is on, the Switched Live becomes live as it takes power to the light. And this wire is in the color blue or grey. 

Most importantly, you can see a brown sleeve on Switched Live. This sleeve indicates that the wire is a live wire, no matter what the color of the wire is. 

What Are the Four Wires on a 3-Way Switch?

The four wires on a 3-way switch are similar to the wires already in it. However, the 4-wire cable has a red wire aside from the bare copper wire, white wire, and black wire of the 3-way switch. Below are the wire colors and what each color means: 

  • Bare Copper: Ground 
  • White Wire: Neutral
  • Black Wire: Hot or power wire
  • Red Wire: Hot or power wire

Where Does Hot Wire Go On a 3-Way Switch?

The 3-way wire is located on the left of the switch then runs to the right side. The left part of the switch is where the black “hot” wire enters. While the black and red wires carry the output from terminals to the left switch, and the white one carries ground. 

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How Do You Wire a 3-Way Switch to a 4-Wire?

If you have two 3-way switches, you can wire it to a 4-way switch. If none, you may need to have two 3-way switches before you can wire it to a 4-wire. That being said, here are easy steps on how you can wire a 3-way switch to a 4-wire if you plan to do it on your own: 

Step 1. Turn Off the Power

Before doing anything, it’s best to turn off the power. Do so by checking and removing the fuses or turning the breakers off. To make it even safer, put some tape over the breaker handle or put a warning sign to inform your housemates that you’re working on the circuit. 

That way, your housemates will not try to switch it on while you’re working. 

Step 2. Unscrew and Pull Out the Switch

Next is to unscrew the cover plate; two screws hold each switch in place aside from the two screws in its cover plate. Then, pull out the switch. To do this, grasp the “ears” of the switch. Be careful when doing this step so that you will not touch the wires on the sides.

Or better yet, use a voltmeter to ensure that the circuit is off before touching any bare wires. 

Step 3. Remove the Wires

Here, you must not disturb the four wires or cables in the wall box. Instead, remove them from the switch’s terminationsYou can do this by bending the wires from under the side screws after loosening the screws. Or you can pull them out if they’re pushed into a small hole in the switch’s back. 

Since these wires are stuck together, the cutting must be close to the switch. And for the new switch, you can strip about half an inch of insulation from the wire’s end

Step 4. Fold the Wires Before Connecting

Then, fold the wires out of the box, bottom down, and top of the switch. Doing this will give you a sign where you should terminate them on the new switch. This action will also help you prevent having a hard time looking where each wire is coming from. 

Instead of simply pushing the wires into the new switch when connecting the wires, it’s best to hold them together with screws. By doing this, you can prevent the connections from loosening as years pass by. 

Now, you’ll see two wires in each switch’s cable. The wire from the cable will terminate the two screws on the bottom. And the two screws on the top will be terminated by the two wires from the other cable. The last wire, which is entirely bare of insulation or has a green color, will go to the green screw. You can find this green screw near the ground wire and end of the switch. 

Step 5. Return the Switch

The last step is to put the switch back into the box. Here, make sure that the wires are not alongside the box, but keep them behind the switchTo make this easier, you may have to separate the two screws from the cover plate and the switch box. Then, put back the screws holding the switch and the cover plate.

Doing this will help you determine which screws go to the plate and the container.

What Is the Red Wire in a 3-Way Switch?

The red wire is another wire color in an electrical system, similar to the black wire. These wires are considered the second hot or traveler wire, and they will become hot if the toggle switch is on. However, the black wire will become hot while the red wire will not or vice versa.

It means that the two wires will not simultaneously become hot and only one of them. 

What Color Wire Goes to the Black Screw On a 3-Way Switch?

The common wire with a black color should also attach to the black screw, or in some cases, the darkest shade. Sometimes the black screw terminal has a COM label. Familiarizing yourself with this label will be a better option to identify the black screw terminal quickly.

wire color


How Do You Wire Up a 3-Way Switch?

Whether you have an existing switch or are still planning on your switches, you may want to consider a 3-way switch. As mentioned, the advantage of having a 3-way switch outweighs a single-pole switch. With such, here are the steps you can follow when wiring a 3-way switch:

  1. First, have an extra electrical box for the second 3-way switch. You might also have to replace your existing box with a larger one so you can accommodate the additional wires you’ll be using. 
  2. Then, switch off the electrical panel’s circuit.
  3. Next is to have 12-3 cable for 12-gauge wire or 14-3 cable, which usually has red, black, white, and bare ground wire for insulated conductors. Feed these between the two boxes
  4. Use ground screws to connect the wires to the new 3-way switches. Here, you can find labels on the common terminal to identify the switches. For some, they have different colors for the terminal screws. 
  5. For the white wires that you’ve used as travelers, wrap their ends with black electrical tape. It would help if you did this so that others will become aware that such wires are “hot” wires. 

How do you bypass a 3-way switch?

You can also bypass your 3-way switch if you want only to have a single-pole switch. Start by switching off the fuse box or circuit breaker. Bypassing your switch is also possible using a “jumper,” which is a short run of copper wire. This way allows you to avoid removing the switch. Or you can also follow the ways below:

  1. Start by replacing your current switch with a single-pole switch.
  2. To the load side, you can connect any of the traveler wires
  3. Then, connect the same traveler wire to the Switched Hot wire to the lights after removing the unwanted switch.
  4. Lastly, abandon the unused traveler wire

The Bottom Line

By knowing the things above, you can easily make your single-pole switch to a 3-way switch. Or you can use this information to turn your 3-way switch into a 4-wire switch. Nonetheless, it’s essential to familiarize yourself with such things to work on your switch will not be a trial and error

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