Breaker Off

Breaker Off / Light switches

Light switch wiring, power at the light

One cable in the switch box with a black and a white wire (the white should have black tape on it), and two cables in the light box.

Where the power comes in

At the switchtwo cables in the switch boxAt the light, no neutralone 2-wire cable at the switchAt the light, with neutralone 3-wire cable at the switch

What goes in the box

SwitchDimmerSmart switch

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

PanelLight boxSwitch boxLight fixtureSingle-pole switch14/2 NM-B14/2 NM-B BREAKER NEUTRAL BAR GROUND BARLINELOAD
PanelLight boxSwitch boxLight fixtureSingle-pole switch14/2 NM-B14/2 NM-B BREAKER NEUTRAL BAR GROUND BARLINELOAD

How to tell this is your box

Power is at the light when the switch box has only one cable. That cable is a switch loop: the white wire carries power down to the switch and the black brings it back to the light.

Watch for this. This switch box has no neutral. Most smart switches need one. Use a model made for no-neutral boxes, or run a new 3-wire cable.

The job, in order

  1. In the light box, join the black from the panel to the white wire going down to the switch. Tape that white black at both ends so the next person knows it is hot.
  2. Connect the black wire coming back from the switch to the fixture's black lead.
  3. Connect the white from the panel to the fixture's white lead.
  4. In the switch box, the taped white and the black go on the two screws; ground to the green screw.

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 switch join under one wire nut.
  • The black wire to the 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 switch join under one wire nut with a ground pigtail to the fixture's ground.

In the switch box

  • The white wire (taped black) from the light goes to one brass screw.
  • The black wire from the light goes to the other brass screw.
  • The bare copper wire from the light goes to the green ground screw.

Parts for this box

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Other boxes on this circuit