8" Round Motorized Damper - Normally Closed - 28 GaugeFAMCO ADC824 8" Round Motorized Damper Normally Closed 28 Gauge The FAMCO ADC Motorized HVAC Damper Normally Closed is normally closed with a power open and spring return motor assembly. The ADC is made with 24 volt or 120 volt motors. End switches are available with all models. End switches allow another appliance to be operated when the damper has reached its full power (either open or closed). The floating motor mount assures proper alignment of