The 820AL is a manual, aluminum opposed blade damper with a locking quadrant to regulator airflow in square or rectangular duct systems. The opposed blade design distributes air evenly over the face of the damper, thereby reducing noise and turbulence when damper is restricting airflow. Individual synthetic blade bushings prevent the blade pivot from rattling in the frame. This is a high free area damper for lower pressure drop across the damper.
The 820AL provides a locking quadrant with a position indicator. The 820ALN provides a locking quadrant on a 1″ base for an exterior insulated duct. The 820ALN-2 provides a locking quadrant on a 2″base.And the 820ALN-3 provides a locking quadrant on 3″ base.
The damper is 2 1/8″ deep and the blades are contained within the frame.