How to Wire a Bath Exhaust Fan

A typical bath exhaust fan

A bath exhaust fan prevents mold and mildew in the bathroom by venting moisture to the exterior of the house. How difficult it is to install a bath fan depends on the layout of your home. The easiest do-it-yourself method of installing a fan is to put one in place of an existing ceiling light, wiring the fan to the same circuit and controlling it from the same wall switch. This approach will work only for bathrooms with unfinished attics above.

Things You'll Need

• Ladder
• Screw gun
• Exhaust fan kit
• Pencil
• Jigsaw
• Twist-on wire caps
• Electrical tape

Instructions

1. Turn off the current to the existing ceiling fixture at the circuit box. Remove the existing fixture by taking out the mounting screws that hold it to the ceiling. Disconnect the wires. Discard the current fixture.

2. Move to the attic above the bathroom and locate the electrical box on the floor. Pull out the wiring that runs into the box from the house circuit, loosening the screws around the wire clamp that holds the bundle of wires in place. You should have loose and exposed wire ends, with the other end of the wiring still connected to the house circuit.

3. Remove the electrical box from the flooring, taking out the screws that mount the box to the floor joists and revealing the hole in the bathroom ceiling.

4. Set the fan unit over the hole on the floor of the attic. Use a pencil to trace the edge of the vent onto the floor. Cut out the area with your jigsaw. Place the fan back down, so the vent drops through the hole. Secure the unit to the joists using the mounting screws that came with the unit.

5. Install the exhaust hose from the unit to an exterior attic wall. Cut an appropriate hole in the wall by tracing around the opening of the hose and using your jigsaw. Secure the hose with the provided screws.

6. Connect the black wire from the fan to the black wire from the house by holding the exposed ends of the wires side by side and twisting a wire cap over both of them. Wrap the connection in electrical tape. Follow the same procedure with the white wire from the fan and the white wire from the house. Twist the bare copper grounding wire from the house circuit to the green ground screw in the fan unit and tighten.

7. Return to the bathroom and install the vent cover on the ceiling, using the provided screws. Turn on the electricity at the circuit box and test the fan at the wall switch.

References

• ThisOldHouse.com: Installing Bathroom Exhaust Fans.