How to Wire Two Dimmer Switches in the Same Box

Choose a dual dimmer control style. Switches are available with stacked rotating knobs, stacked push controls and side-by-side vertical sliders.

Cut off the power supply running through the circuit that feeds the box. Turn off the breaker switch and lock or label the breaker box to avoid accidental reactivation of power.

Remove the existing switch. Unscrew the two machine screws holding the faceplate with a slotted screwdriver. Use a phillips screwdriver to remove the upper and lower mounting screws securing the switch. Pull the switch out of the box by one of the mounting fins and touch the leads of a volt tester against the contacts to verify that the power is off.

Identify and mark the hot wire. The hot wire is typically black and connected to a common terminal that has a dark or bronze colored terminal screw head. Some switches have break-off fins on the hot terminal. Turn the power back on and find the hot wire with a volt tester if nothing else positively identifies it. Touch one lead from the volt tester to the ground terminal and check the others with the opposite lead to find the one that shows power. Turn off the breaker switch before proceeding. Mark the hot wire with masking tape. Mark the connected wires to show which works the fan and light, if you are replacing a combination unit.

Unscrew the terminals and remove the wires from the old switch. Cut the bare wire ends off with wire cutters and strip each to expose 1/2 inch of wire. Use wire cutter blades to splice off the insulation around the wires.

Install the wires on the dual switch. Wrap the hot wire around the black colored terminal screw with clockwise rotation. Tighten the terminal screw with a Phillips screwdriver, covering all exposed wire. Connect the fan wire (if applicable) to the brass terminal marked "switch." Connect the light wire to the brass "dimmer" terminal. Outgoing power can connect to either brass terminal if the dimmers will control two lights. Let the white neutral run from the incoming raceway to the outgoing one. Twist the neutral wires together and cap the connection with a wire nut if necessary. Run a ground wire from the ground terminal on the switch to the ground terminal in the back of the box.

Press the wires carefully into the box and push the switch unit into position so the mounting screw holes align with the holes in the upper and lower box. Replace the mounting screws. Put the faceplate over the switch and replace the holding screws.

Turn the power back on at the breaker box. Test the operation of the new dual dimmer switches with the lights or fan/light combination.