Though you might not expect to need to change a vent fan's direction, this could become a necessity. Perhaps you're in the middle of renovations and need to change the flow of air or the motor to the fan broke and the replacement arrived rotating in the wrong direction. Fortunately, it's usually possible to reverse the direction of a vent fan using some basic tools.
Why Vent Fan Direction Matters
The direction in which a vent fan's blades rotate has an impact on its ability to function properly. When the blades turn clockwise, the air is drawn upwards; counterclockwise, and the air is blown straight down. Some vent fans can change their polarity with a simple switch, but most don't have this feature.
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If a vent fan is rotating the wrong way, it may be fixable. While not all vent fans can reverse their blade direction, certain fans that use alternating current (AC) motors can, such as a 110-volt AC motor and certain shaded pole motors.
Unfortunately, many motors can't be reversed. Most often, motors are designed to operate in a single direction. Check the model number on the vent fan's motor to determine if a reversal is even possible before starting the process.
Reversing AC Motors
AC motors are induction motors in which wires and magnetic fields power rotation. Changing the rotation direction of these motors requires switching the wire connections. You should only proceed with this project if you're well-acquainted with electrical work. Otherwise, you should call in a professional electrician.
You'll need just a screwdriver or wrench for this project, depending on the vent fan structure. Before proceeding, make sure there's no power running to the vent. Unplug it and switch off the connected circuit breaker. Once you're sure there's no power, you can remove the vent cover.
Keeping the screws nearby and organized, set the fan cover aside and remove the blade shroud to uncover the motor. Depending on the vent, there may be a few other components in your way. Carefully remove all necessary pieces, being sure not to lose any important hardware in the process.
Electrical Wires and Reassembly
Once you've reached the motor, you'll want to access the wires underneath. They'll be protected by a metal covering — or plastic on some models — and secured with nuts or screws. Remove the covering and set it aside.
The electrical wires will be neatly tucked beneath the covering, connected to the motor's coils. Carefully loosen the wires' connections and switch them to the opposite coil. This should change the fan's polarity, allowing it to run in the desired direction.
Reattach the electrical wires' covering, tightly securing the fasteners back in place. Secure the shroud and all other parts back to the motor and vent housing in the correct order. Once everything is back in order, reattach the vent cover and return power to the vent.
Shaded Pole Motor Reversal
Shaded pole motors are a specific type of AC induction motor with a pole that connects to the blades and a copper ring called the shading coil. The fan's rotation is determined by the direction the unshaded side of the shading coil faces. A shaded pole motor can be reversed by flipping the frame 180 degrees. To do so, carefully disconnect the blade from the pole and unscrew the motor from the frame.
Using caution, remove the motor on one side of the frame and the backing on the other. Now that all of the pieces are removed from the frame, flip the frame 180 degrees so the copper ring's shaded side faces the opposite direction from where it began. Reassemble the motor with the frame facing its new direction.