The 820ALP is a manual, aluminum opposed blade damper with a mounting plate 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 galvanized steel mounting plate enables simple slip-in installation by cutting a 2 1/4″slot in the side of the duct and securing the damper plate with the 4 screw holes (screws by others). A commercial quality locking quadrant to operate and lock the blades in place is included.
The 820ALP has side duct control and is furnished with a 403 lever-type locking regulator with a 3/8″ operating shaft. The 403 locking regulator has a position indicator.