How to Wire 3-Position Timer Switches

Wire a three-position timer to control electrical devices.

Although called a three-position timer switch, it's a bit of a misnomer as usually one of the positions is "Off." A three-position timer switch controls two circuits, enabling you set the time you want electrical items to operate. Electrical power enters the timer and then splits into sections so that you have a single power-in terminal and two power-out terminals. Wiring is relatively straightforward, but it is sensible to have the user instructions handy because wiring and terminal labeling may differ, depending on the manufacturer.

Things You'll Need

• Screwdriver
• Wire strippers

Instructions

1. Remove the screws on the back plate holding the front cover of the three-position timer switch in place using a screwdriver. Lift off the front cover to access the terminal connections. The terminal connections are all clearly labeled, but have your user instructions nearby so you refer to them if you need to.

2. Loosen the small screws on the power-in terminal connector. There are three, and they are labeled "Gnd," "Neu" and "Hot." The labeling may be slightly different, so check the user instructions if necessary.

3. Insert the three wires from the power source under the three terminal screws. The black wire goes to "Hot," the white wire goes to "Neu" and the green wire goes to "Gnd." Tighten the three screws. If the wires are not already stripped, then remove 1/4-inch of plastic from the end of them using wire strippers to expose the bare metal. If the wire has an outer protective covering, then strip about 1 inch off to expose the three internal wires.

4. Loosen the screws on the terminals on the opposite side of the three-position timer switch. Each terminal block usually has three screws, but check the instructions if you find the layout is different.

5. Insert the wires from one of the electrical appliances that the three-position timer operates under the screws on one of the two terminal blocks. It doesn't matter which one. The terminal screws are labeled "Com" or "Hot, "Neu" or "A" and "Gnd." Insert the black wire under the "Com" screw, the white wire under the "Neu" screw and the green wire under the "Gnd" screw. If you need to strip the wires to expose the bare metal, then use wire strippers as before. Tighten the three screws.

6. Repeat the process for the wire connected to the other electrical appliance the three-position timer operates. The labels on the terminal block are the same, except the "Neu" terminal may be labeled "B."

7. Replace the cover on the three-position timer switch. Replace the screws in the back plate, and tighten them using a screwdriver.

8. Connect the three-position timer to the power supply.

References

• All About Circuits: Wiring Color Codes
• National Fire Protection Association: NFPA 70