How to Reverse Attic Fans

Whole house fans are used to blow hot air out of the attic by sucking cool air through the house up though the whole house fan and out though the gable vents in the attic. These fans are usually wired to run in one direction. Some whole house fans, however, can be reversed to spin in the opposite direction. The reversible fans usually have a reverse wire, which can be connected to reverse the direction of the motor. Not all fans are reversible. Check your manufacturer's documentation to see if it can be reversed.

Things You'll Need

  • Wire cutters

  • Wire strippers

  • Manufacturer's documentation

  • Plastic twist caps

Step 1

Locate the manufacturer wiring diagram for the motor that powers the whole house fan. This information will be in the manufacturer's documentation that came with the fan, or the manufacturer will have to be contacted for the the information.

Step 2

Look at the wiring diagram and see if the motor has a startup winding. If a startup winding is present, the motor can be reversed. If a startup winding is not present, the motor cannot be reversed.

Step 3

Locate the two end wires of the startup winding. Disconnect each of the two wires and reverse their connections. For example: if wire "A" of the startup winding is connected to terminal "A" and wire "B" is connected to terminal "B," then the motor can be reversed by connecting wire "A" to terminal "B" and wire "B" to terminal "A."