Can speed controls made by other manufactures be used with Air Vent roof-mount power fans?

You cannot use speed controls from other manufacturers with Air Vent power fans.

 Air Vent motor bearing products have a UL approval based on the power supply of 110 to 120V with sufficient amperage to operate the motor at full speed. The concern with modifying the motor speed has to do with the insulation class rating of the motor. By altering the power supplied to the motor, elevated motor winding temperatures could result which could lead to premature motor failure.