Timer switches are intended to turn an electrical apparatus on or off at specific times, to automate the times when the unit is in use. Generally used with landscape lighting and sprinkler systems, electrical timers may often replace single-pole switches. In some cases, a timer switch may require installation where only the hot results are switched. It is possible to replace a single-pole switch with a timer switch with no neutral connection based on the timer’s wiring diagram in a few minutes with some simple hand tools.
Turn off the breaker to the electrical circuit to the timer switch will be connected at the breaker panel.
Loosen the plate cover screws with a screwdriver and remove the plate cover over the existing switch. Hold the tip of a noncontact electrical tester from the wires on the switch. If the light on the tester illuminates, flip off more the main breaker to the electrical panel, and retest until the tester light no longer comes on.
Loosen the mounting screws and pull the switch out of this switch box. Loosen and remove the screws on the wiring terminals, and pull on the wires off of the terminals. Set the switch apart.
Clip off the bare wire loops on the ends of the wires in the switch box with the cutting tip of a pair of wire strippers. Subsequently strip 1/2-inch of insulation from the ends of the wires.
Connect the black lead cable from the electrical panel to the hot wire on the switch (usually a black cable) with a wire nut. Ask your timer’s wiring diagram to make certain which cable is the hot lead from the switch. Then connect the switched wire (usually a blue cable) to the black wire resulting in the device. Finally, connect the wire from the switch to the bare wire in the switch box.
Push the wires into the switch box and mount the switch box with the two mounting screws. Place the switch cover over the switch and tighten the screws to mount the cover.
Turn on the power to the switch, and put the timer to manual mode to check the operation of the apparatus. If it tests properly in manual mode, set the timer as per the operating instructions for the switch.