> Building Automation > Damper Actuators > LF24-SR,8770003000,Spring Return Actuator for Open/Close Damper Actuation 4 Nm (3 ft-lbf) 
The LF24-SR is a 24 V modulating damper actuator intended for operation of air dampers of up to approximately 0.8 m2 (8.6 ft2) cross sectional area that perform safety functions, e.g. frost and smoke protection, hygiene, etc.
Control is effected by means of an electronic controller with a signal of 0–10 V DC and a continuous position feedback of 2–10 V DC.
Either direction of rotation can be selected.
The spring return operates as a safety function if the power supply fails or is interrupted. The spring pretensioning can be manually adjusted.
Power supply 24 V AC ±20%, 50–60 Hz,24 V DC -10%, +20% Power consumption opening 2.5 W open 1 W For wire sizing 7 VA (Imax=5.8 A for 5 ms) Connection cable 1 m (3.3 ft), 4×0.75 mm2 (AWG 18) Angle of rotation max. 95° (adjustable 37–100% with additional limit stop ZDB-LF) Torque Actuator min. 4 Nm (3 ft-lbf) (at rated voltage) Spring return min. 4 Nm (3 ft-lbf) Running time 150s Actuator 40–75 s (0–4 Nm (0–3 ft-lbf)) Spring return approx. 20 s (at -20 to +50 °C (-4 to +122°F)), max. 60 s (at -30 °C (-22°F)) Direction of rotation selected by mounting L/R Position indication mechanical Standards conformity EMC, emission SS EN 50081-1 EMC, immunity SS EN 50082-1 Protection class III (safety extra-low voltage) Enclosure rating IP 54 Ambient humidity EN 60335-1 Ambient temperature: Operation –30 to +50 °C (–22 to +122 °F) Storage –40 to +80 °C (–40 to +176 °F) Sound power level Actuator max. 50 dB (A) Spring approx. 62 dB (A) Service life min. 60 000 operations Maintenance maintenance-free Weight: 1.4 kg (3.1 lb.)
