The ZD is a power close and spring open damper. It has a 24 V 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, 2-wire installation|Reliable, strong, 24 VAC spring-return motor|Fail-safe, normally open operation|Damper can be installed in any orientation mounting on side of the duct
Honeywell Home Damper, Series: ZD Series, 14 x 14 in, Rectangle, 24 VAC, 0.32 A, 90 deg Rotation, 30 sec Power Open/10 sec Spring Return Timing, Parallel Blade, Power Open/Spring Closed Motor, M1-Power/M6-Common/M4-LED Indication Terminal, 40 to 140 deg F, Aluminum