Conserving electricity is not easy to do. Especially when there are so many small ways we unknowingly waste it. One such wasteful way is by having your bathroom exhaust fan and light wired to the same switch. Sure, you need the exhaust on while you're showering, but you don't need it on when you're simply brushing your teeth. By taking the time to wire each component independently--you can prevent the unnecessary waste of quite a bit of electricity over the course of a year. Here is how to do it.
Turn off the circuit that delivers power to the bathroom exhaust fan/light.
Remove the cover plate from the existing switch. Remove the two screws that secure the switch to the wall box and gently pull the switch out using the top and bottom tabs.
Once the switch is out of the wall box, use your voltage tester to double-check that the power is definitely off. Loosen the terminals on the sides of the switch and remove the wires. Follow them back into the box so you know which set is going to the fan kit.
Remove the lens and light bulb from the light/exhaust fan assembly. Since most connection boxes for these units are located externally, you will have to unseat the unit from the ceiling joists. Access above the bathroom ceiling may be required in order to detach the exhaust fan.
With the ceiling fan free, position it so you have easy access to the connection box. Remove the cover plate. Inside, remove the wire connectors and separate the wires. Follow the leads to discover which wires feed the light and which ones feed the fan. Label them with a piece of tape so you don't forget.
Remove the existing feed wire from the fan's connection box.
If the existing feed leg is not stapled to the ceiling joists, you can tie the new cable to the existing one and pull it from the switch box to the exhaust fan's access hole. If the existing feed is stapled, then you will have to use a non-metallic fish to run the new line. If this is the case, you may have to cut an access hole in the ceiling and on the wall above where the switch is located to make it easier to run.
If you use the fish to run the wire, then make sure you cut away as much of the old wire so you don't accidentally wire it up to a live circuit at some point.
With the new wire run, strip away about 6 inches of outer sheathing on both ends using the ROMEX® stripper.
At the exhaust fan's connection box, insert the new cable through the connector on the box and secure the clamp down over a portion of the cable that still has the outer sheath on it. Use your wire strippers to remove about 3/4 inches from the ends of each individual wire.
Connect the white wire from the feed cable to the two white wires in the connection box. Connect all of the ground wires together. Connect the black wire from the feed cable to either the fan lead or the light lead and the red wire from the feed cable to the other.
Make sure all of the wire connectors are on tight and wrap a length of electrical tape around each set of wires. Replace the cover plate and resecure the exhaust fan assembly to the ceiling. Reinstall the light bulb and the cover lens.
Take the double pole toggle switch combo and loosen all of the terminals. On the left-hand side of the switch, connect the feed wire that is coming from the panel. On this side, the top terminal will be left empty, so just tighten down the terminal so it is not protruding unnecessarily.
On the right side of the switch, use needlenose pliers to remove the metal tab that bridges the two terminals.
Connect the black wire that is heading to the exhaust fan kit to one terminal and the red wire to the other terminal. Connect the white wire to the other white wire(s) in the box. Connect the ground wire with the other ground wire(s) in the box and use a spare piece of copper wire to make a pigtail. Connect the pigtail wire to the ground screw on the switch.
Wrap electrical tape around the switch so the terminals are covered and gently push all of the wires back into the box. Secure the switch to the box and install the new cover plate.
Turn the circuit back on and test out your independently wired bathroom light and exhaust fan. Now you can run the exhaust fan only when you need to and not every time you enter the bathroom.