Overview 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. Product Specifications ApplicationParallel Blade DamperUsed WithHoneywell zoning systemsVoltage24VSize (in.) 8 in. x 18 in.Blade ActionParallelShape rectangularMotor or Actuator Mounting BottomMotorpower closed, spring openMotor Timing30 seconds power open/10 seconds spring returnWires to Motor2Other Motor InformationRange stops