LF120 US | Belimo | Damper ActuatorLF120 US Damper Actuator, On Off, 120 VAC, spring return (fail safe) For On Off, fail safe control of dampers in HVAC systems. Actuator sizing should be done in accordance with the damper manufacturers specifications. Control is On Off from an auxiliary contact or a manual switch. The actuator is mounted directly to a damper shaft from 3 8 up to 1 2 in diameter by means of its universal clamp, 1 2 shaft centered at delivery. For shafts up to 3 4 use