The Young Regular Model 821A dampers are standard, manual, opposed blade volume control dampers, that regulate airflow in square or rectangular duct systems. The 821A is controlled from the face of the damper with a Phillips screwdriver. Individual Teflon blade bushings provide smooth, quite operation for the life of the damper. This is a high free area damper for lower pressure drop across the damper. The gear rack converts rotational motion into linear motion when the spur gear is run against it. A gear that turns to move the rack is fastened to the stainless steel slide mechanism and is held in place with a Nylock nut that maintains pressure and resistance to prevent the blades from moving under higher velocities or pressures. The opposed blade design provides more uniform air control reducing turbulence and lowering noise levels.
The model 820AC is controlled from the bottom of the duct with a bearing/coupling and is frequently used with the Young Regulator model 301 or 315 Concealed Ceiling Regulator.