How to Wire a Three Way Wall Switch

Preparation

• 1

  Connect the 12/2 wire to a circuit breaker on the electrical panel. The 12/2 wire has two wires---each a 12 gauge. One is a white wire (neutral) and one is a black wire (hot). Run the wires to the location of the first 3-way switch, and secure it in place.

• 2

  Run the 12/3 wire from the first 3-way switch location to the second one. The 12/3 wire contains three wires, one white, one black and one red. The red and black wires on the 12/3 wire are the traveler wires.

• 3

  Run a 12/2 wire from the second 3-way switch to the light fixture, the black wire from the fixture to the second switch is the common wire, and the white wire is the one coming from the electric panel.

Connection

• 4

  Splice the wire, then connect the white wire from the 12/2 wire---coming from the electric panel---to the neutral wire on the 12/3 wire---going from the first switch to the second one. Neutral wires are not attached to any terminal screws on the 3-way switch; they run continuously from the electric panel to the light fixture. All white wires are connected to each other using wire nuts.

• 5

  Connect the black wire on the 12/2 wire---coming from the electric panel---to the common terminal screw on the first switch. The common terminal screw is on the switch's side and is normally black or in a different color from the other two screws in the same location.

• 6

  Join the 12/3 wire to the remaining two terminal screws on the 3-way switch. The white wires connect to the white wire coming form the electric panel, using a wire nut. The black and red wires connect to the other two terminal screws. It does not matter which color goes to which terminal, as long as you connect them the same exact way on the second 3-way switch. Some electricians prefer to keep black wires on one side of the 3-way switch and red wires on the other side, for ease of installation.

• 7

  Connect the 12/3 wire on the second switch, as follows: The neutral or white wire will be connected to the white wire going to the light fixture. The traveller wires from the 12/3 wire will be connected to the same screws as on the first 3-way switch.

• 8

  Join the black wire going to the light fixture to the common screw on the second 3-way switch.