The FAMCO™ ADC motorized HVAC damper - normally closed is normally closed with a power open and spring return motor assembly. The ADC is made with 24 or 120 V motors. End switches are available with all models. End switches allow another appliance to be operated when the damper has reached its full power (either open or closed). The floating motor mount assures proper alignment of motor, shaft and damper to prevent binding, while the clutch/coupler reduces the number of moving parts for greater service life. All units without the end switch come with a flow control adjustment so that the damper blade can be blocked from opening or closing 100%. (Note: the end switch will not work if the flow control adjustment is preventing the damper from reaching it's full potential.) Quality constructed in 28 ga galvanized steel.