Breaker Off

Breaker Off / 3-way and 4-way switches

3-way dimmer wiring, power at the light

Two cables in the light box. A 2-wire cable runs to the first switch, and a 3-wire cable runs on to the second switch.

Where the power comes in

At the first switchthe panel cable is in a switch boxAt the lightthe panel cable is in the light box

What goes in the box

3-way switches3-way dimmerAdd a 4-way

The breaker is off: every wire is dead and safe to work on. Tap a switch in the drawing to flip it.

PanelLight boxFirst switch boxSecond switch boxLight fixture3-way dimmer3-way switch14/2 NM-B14/2 NM-B14/3 NM-B BREAKER NEUTRAL BAR GROUND BARCOMMONTRAVELERTRAVELERCOMMONTRAVELERTRAVELER
PanelLight boxFirst switch boxSecond switch boxLight fixture3-way dimmer3-way switch14/2 NM-B14/2 NM-B14/3 NM-B BREAKER NEUTRAL BAR GROUND BARCOMMONTRAVELERTRAVELERCOMMONTRAVELERTRAVELER

How to tell this is your box

Power is at the light when the light box has the cable from the panel. The whites in the switch boxes then carry power, not neutral, and should be taped black.

The job, in order

  1. Light box: join the black from the panel to the white going to the first switch, and tape it black.
  2. The black coming back from the first switch's COMMON goes to the fixture's black lead.
  3. First switch box: join the taped white from the light to the white going on to the second switch (taped too). Black and red in the 3-wire cable are the travelers.
  4. Second switch: the taped white goes to the dark COMMON screw; black and red to the brass traveler screws.

Every connection, box by box

Read from the same circuit the drawing is made from. A simulator checked it in every switch position: the light turns on exactly when they should, nothing shorts, and every device is grounded.

At the panel

  • The black wire to the light goes to the breaker.
  • The white wire to the light goes to the neutral bar.
  • The bare copper wire to the light goes to the ground bar.

In the light box

  • The black wire from the panel and the white wire (taped black) to the first 3-way switch join under one wire nut.
  • The black wire to the first 3-way switch goes to the fixture's black lead.
  • The white wire from the panel goes to the fixture's white lead.
  • The bare copper wire from the panel and the bare copper wire to the first 3-way switch join under one wire nut with a ground pigtail to the fixture's ground.

In the first switch box

  • The white wire (taped black) from the light and the white wire (taped black) to the second 3-way switch join under one wire nut.
  • The black wire from the light goes to the COMMON lead.
  • The black wire to the second 3-way switch goes to one traveler lead.
  • The red wire to the second 3-way switch goes to the other traveler lead.
  • The bare copper wire from the light and the bare copper wire to the second 3-way switch join under one wire nut with a ground pigtail to the green lead.

In the second switch box

  • The white wire (taped black) from the first 3-way switch goes to the dark COMMON screw.
  • The black wire from the first 3-way switch goes to one brass traveler screw.
  • The red wire from the first 3-way switch goes to the other brass traveler screw.
  • The bare copper wire from the first 3-way switch goes to the green ground screw.

Parts for this box

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Other boxes on this circuit