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How to Wire a Light From the Breaker Box

Jonra Springs

Install a new light with a separate breaker switch on the panel and a light switch on the wall. The wiring is less of a challenge if the home or room is unfinished with no insulation or drywall on the rafters and studs, but electrical wiring can be installed inside finished walls, too. Safety must be the first consideration for work on an electric breaker panel. Work consciously and pay attention to details to successfully install your new lighting.

Industrial electrician at work.
  1. Review the national and local electrical codes for specifications on wire gauge, and check torque settings listed for panel terminals. The national code calls for 12-gauge electrical wiring. The panel will specify a torque for tightening the terminals.

  2. Place the patterns cut out from the light box and switch box onto the ceiling and wall drywall of a finished room. Use a step ladder to reach the ceiling location. Position the switch box pattern at an appropriate level on the wall with a side edge next to a stud. Place the light box pattern next to a rafter. Trace around the patterns with a pencil. Put on eye protection and cut out the shapes with a drywall saw. Secure the boxes to the adjacent framing wood with the hardware provided, which will consist of wood screws or nails.

  3. Turn off the main breaker panel switch. Be mindful of the thick wires that bring power into the panel. These remain live despite shutting off the power that runs through the house. Do not touch the incoming wires with fingers or any metal.

  4. Run 12/2 Romex behind the walls from the breaker box to the switch box, then from the switch box to the light box. Use a fish tape to draw the wiring up through the walls and into the attic. Leave 8 inches to 10 inches of excess electrical wiring at both boxes, and 12 inches to 14 inches at the breaker panel.

  5. Remove the cover from the breaker panel with a Phillips screwdriver. Push 10 inches of the Romex raceway through a slot in the top of the panel and secure it with a cable clamp. Slice the Romex shield around the wires and cut it away near the slot inside the box.

  6. Strip the black and white wires with wire-cutter blades to expose an inch of bare wire. Unscrew a terminal on the ground bus bar and thread the copper ground wire into it with needle nose pliers. Set the torque wrench to the specified torque and tighten the terminal with the screwdriver attachment. Connect the white neutral wire from the raceway to an open terminal on the neutral bus in similar fashion.

  7. Connect the black hot wire from the raceway to a single pole 15-amp breaker switch by unscrewing the terminal and feeding the bare wire into the terminal jaws. Tighten the terminal screw firmly with a slotted screwdriver. Plug the breaker switch into an open port in the panel, securing the holding clamps to the holding bar and fitting the connection prongs into the slots. Break the cover plate off the panel cover for that switch location with slip slot pliers, replace the cover and tighten the panel cover holding screws.

  8. Push 5 inches of the Romex through the overhead light box from the attic. Slice the shield and cut it away from the step ladder. Strip the black and white wires to expose 1/2 inch of wire. Connect the ground wire to the ground terminal inside the light box. Connect the black hot wire to the brass-colored socket terminal on the lighting rig and the white neutral wire to the silver terminal. Wrap the wires around the terminals with clockwise turns. Cover all bare wire by tighten the terminal screws. Screw light bulbs into the sockets on the rig. Cover with an overhead lighting globe.

  9. Push 5 inches of the Romex from the breaker panel through the bottom or back of the switch box. Push an equal amount of Romex from the light box through the top of the light box. Slice and cut away the shield from both, and strip 1/2 inch from both sets of hot and neutral wires. Cut off 3 inches of the ground wire from the top raceway. Twist the 3-inch ground wire around the ground wires from both raceways and cover the connection with a wire nut. Twist the loose end of the 3-inch ground around the ground terminal at the back of the switch box, and tighten the ground terminal screw.

  10. Twist the white neutral wires from both raceways together and cap the connection with a wire nut. Connect the hot wires to the brass terminals on one side of the switch. Secure the switch inside box with the mounting screws. Cover the switch with a plate and tighten the screws to hold it in place.

  11. Double check all connections at the breaker panel, switch box and light box. Turn the main panel switch on and turn on the light switch at the wall.