Adjustment of fan blade pitch is needed when there is a dynamic imbalance in the blades that will cause the fan to wobble. This can occur when the blade fittings become bent during shipping or installation. The pitch can be adjusted to factory settings listed in your service manual, or you can modify the pitch to your desired angle range.
Things You'll Need
Turn off the unit and disconnect the power supply. This will avoid any injury from electrical shock while adjusting the fan blades.
Position the bevel protractor on the fan blade near the tip on the concave side of the blade. Measure the degree of pitch on the fan blade. Write the degree on a piece of paper. Tear off a small piece of adhesive tape approximately 2 inches long and write "1" on it with your permanent marker. Place the tape on the edge of the fan blades to mark which ones you have already measured. Repeat this step for the remaining fan blades, marking them in consecutive numbers.
Return to the fan blade marked "1." Support the fan blade with your hand and place the bevel protractor on the concave surface nearest to the tip of the fan blade.
Loosen the U-bolts or retention clamps with your torque wrench on the first blade until you can position the fan blade at the desired pitch angle.
Retighten the U-bolts or retention clamps when the bevel has reached the desired pitch angle. Repeat steps 3 through 5 for the remaining fan blades.