Honeywell - 20" x 8" Rectangular Parallel Blade Damper
Honeywell - The ZD is a power close and spring open damper. It has a 24-volt motor used to control circulating air in HVAC systems and used when a normally-open damper is required. The ZD is typically used with the TrueZONE and other electronic zoning systems.
Mechanical visual position indicator for damper status. Solid construction using extruded aluminum frame and blades. Parallel blade design for low leakage performance. Simple, easy-to-wire, two-wire installation. Reliable, strong, 24-volt spring-return motor. Fail-safe, normally open operation. Ordering Instructions: Order ZD (dimension 1) x (dimension 2). (Motor is always mounted on dimension 2 side.) For example, ZD10x8 is a 10 in. x 8 in. damper with the motor on the 8 in. side; but a ZD8x10 is a 8 in. x 10 in. damper that has the motor on the 10 in. side. Damper can be installed in any orientation (mounting side can be on either the bottom or the side of the duct).