Abstract: A plurality of duct dampers for use with ducts having a plurality of sizes in an HVAC system having zone control. Each of the plurality of duct dampers has a blade for controlling air flow in a duct, an actuator for controlling the position of the blade within a duct, and a shaft attached to the blade for transmitting the actuator control to the blade. The plurality of dampers includes a plurality of blade sizes to correspond to the plurality of duct sizes. A single shaft length is configured for use with the plurality of blade sizes, where one end of the shaft is positioned on each blade according to the size of the blade.

Abstract: An apparatus and improved method for defrosting of the refrigeration unit of a refrigerated vending machine are disclosed. A damper controls flow of heated defrosting air in the refrigeration unit during a defrosting cycle to prevent the heated air from exiting out of the refrigerated air duct leading to the refrigerated compartment of the vending machine, thereby maintaining the desired ambient air temperature within the refrigerated compartment.