Actuators for HVAC shut-off and fire dampers shall be of spring return type.
Pneumatic HVAC actuators shall be designed to operate properly between max. 12.5 barg and min 5.6 barg air supply pressure.
The spring force shall be selected to keep the blade(s) in proper alignment, ensure air tightness in closed position and prevent chattering.
Actuators for HVAC pressure control dampers shall be provided with positioners.