D.I.Y., HOW TO WIRE A FOUR-WAY SWITCH

If you have an existing light fixture which is controlled by two three-way switches (2 different switch locations) and want to add a third switch at a different location, you must install a four-way switch.  If you are building a new home, or putting on an addition and want a fixture controlled for 3 or more locations, you will need to know “how to wire a four-way switch.”

First, in order for the four-way switch system to work, two three-way switches must exist or be installed (as discussed in “DIY,Three-Way Switch Systems”).  Then one or more four-way switches may be installed in line between the three-ways.

You are basically breaking the traveler circuits between the two three-way switches, by installing a four-way switch with its’ double sets of terminals.

Here’s how:

1.  Turn the power off to the circuit.

2.  Select the location of the additional switches and install them as discussed in “DIY, Installing a Receptacle”.  Make sure you are able to install cables from point A to B.  This usually means an interior way with access from the attic above.

Note:  The white wire on the two-wire Romex cable will become a hot wire in the application.  This is legal, but a good rule is to mark it in each box with black tape.

You have now:

3.  Passed the travelers from a three-way to four-way, back to another three-way and on to the fixture.

4.  The physical rough-in work is done and now all that’s left is to tie the wires into the circuit and onto the terminal screws.

• At the first three-way switch, remove the travelers from the terminals and cap off with wire nuts.

• After stripping out the newly run two-wire cable, strip back the black and white wires’ insulation and wrap them in a clockwise rotation around the two traveler terminals of the three-way switch.  Remember, they are the two paralleled terminals opposite to the common terminal.  Repeat this process at the other three-way switch (remembering to tie-in the green or bare bond wires).

• At the four-way switch or switches, tie-in the white and black wire as a pair on the top two traveler terminals.  Repeat on the bottom two terminals for the two-wire cable leading to the other three-way switch or another four-way switch (remembering to tie-in the green or bare bond wires).

• Securely install the devices, re-energize the circuit and test your work.  If all is wired properly, the fixture will turn off and on from any of the locations.

Romex is a registered trademark of Southwire Company.

Related articles

• D.i.y., Wiring a Three-way Switch System (electricauthority.org)
• D.i.y., Adding a Single Pole Switch (electricauthority.org)
• D.i.y., Installing a Surface Fixture, Recessed Fixture or Ceiling Fan (electricauthority.org)
• D.i.y., What Wire to Use, Copper or Aluminum? (electricauthority.org)
• D.i.y., Let’s Wire Your New Bedroom (electricauthority.org)
• D.i.y., What Size Wire to Use? (electricauthority.org)
• How do you wire a switch outlet combo circuit to an existing 3 way light switch (wiki.answers.com)