To wire a variac for controlling a 240V fan, it's crucial to determine the type of motor used; AC induction motors can work with variacs, but shaded pole motors, commonly found in small fans, may not be suitable. The Ruck 6" fan motor operates at 230V and 95W, and it is not a shaded pole motor, which raises concerns about overheating and exceeding variac ratings if used improperly. While some speed regulation is possible with AC induction motors, it is inefficient and can lead to increased heat generation. Proper wiring involves connecting incoming power to terminals 2 and 5, and the motor to terminals 2 and 3. Overall, caution is advised when using a variac for fan speed control to avoid damaging the motor.