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Damper Actuator, 35 in-lb [4 Nm], Spring return, AC/DC 24 V, DC 2...10 V
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Fail-safe position

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Weight 3.4 lbs

35 in-lb




AC/DC 24 V

Actuator Type

Spring return

Control type


Torque motor
35 in-lb [4 Nm]
Power consumption in operation
2.5 W
Power consumption in rest position
1 W
Transformer sizing
5 VA (class 2 power source)
Ambient humidity
5...95% r.H. non-condensing
Housing material
zinc coated steel
Electrical Connection
18 GA plenum cable, 3 ft [1 m], with 1/2" conduit connector
Angle of rotation
Max. 95°,
Position indication
visual indicator, 0° to 95° (0° is full spring return position)
Ambient temperature
-22...122°F [-30...50°C]
Non-operating temperature
-40...176°F [-40...80°C]
Control operating range Y note
4...20 mA w/ ZG-R01 (500 Ω, 1/4 W resistor)
Position Feedback
DC 2...10 V, Max. 0.7 mA
direction of rotation motor
reversible with built-in switch
Overload Protection
electronic throughout 0° to 95° rotation
Input Impedance
100 kΩ for DC 2...10 V (0.1 mA), 500 Ω for 4...20 mA
Degree of Protection
IP54, NEMA 2
Nominal voltage
AC/DC 24 V
Nominal voltage frequency
50/60 Hz
Power Supply
24 VAC, ±20%, 50/60 Hz, 24 VDC, ±10%
Power supply tolerance AC
Power supply tolerance DC
Agency Listing
cULus acc. To UL 873 and CAN/CSA C22.2 No. 24-93
Operating Range
DC 2...10 V, 4...20 mA w/ ZG-R01 (500 Ω, 1/4 W resistor)
Emergency control function
Spring Return
Product family
Damper Actuator
direction of rotation spring-return
reversible with cw/ccw mounting
Noise level, motor
<30 dB (A) 
Shaft Diameter
3/8" to 1/2" round, centers on 1/2"
Electrical accessories
Family Series
LF Series
Noise Level (Fail-Safe)
<62 dB (A) 
Running time (Fail-Safe)
<25 seconds
Running Time (Motor)
150 sec constant, independent of load
Running Time (Fail-Safe)
<25 sec @ -4...122°F [-20...50°C], <60 sec @ -22°F [-30°C]
Fail-Safe function
Spring return
Control type
Degree of protection IEC/EN
Degree of protection NEMA/UL
UL Enclosure Type 2
CAD ThomasNetLink
Product Features
Torque min. 35 in-lb, for control of air dampers.
Electrical Protection
actuators are double insulated
Mechanical accessories
AV6-20|IND-LF|K6 US|K6-1|KG10A|KG6|KG8|KH12|KH6|KH8|KH-LF|KH-LFV|LF-P|SH10|SH8|TOOL-06|ZDB-LF|ZF8-LF|ZG-109|ZG-110|ZG-112|ZG-DC1|ZG-DC2|ZG-LF112|ZG-LF2|ZG-LMSA-1|ZG-LMSA-1/2-5|ZS-100|ZS-101|ZS-150|ZS-260|ZS-300|ZS-300-5|ZS-300-C1|ZS-300-C2|ZS-300-C3
The LF series actuators provide true spring return operation for reliable fail-safe application and positive close-off on air tight dampers. The spring return system provides consistent torque to the damper with, and without, power applied to the actuator. The LF series provides 95° of rotation and is provided with a graduated position indicator showing 0 to 95°. The LF24-SR US uses a brushless DC motor which is controlled by an Application Specific Integrated Circuit (ASIC) and a microprocessor. The microprocessor provides the intelligence to the ASIC to provide a constant rotation rate and to know the actuator’s exact fail-safe position. The ASIC monitors and controls the brushless DC motor’s rotation and provides a digital rotation sensing function to prevent damage to the actuator in a stall condition. The actuator may be stalled anywhere in its normal rotation without the need of mechanical end switches. Power consumption is reduced in holding mode.
For fail-safe, modulating control of dampers in HVAC systems. Actuator sizing should be done in accordance with the damper manufacturer’s specifications. 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 K6-1 accessory. A crank arm and several mounting brackets are available for applications where the actuator cannot be direct coupled to the damper shaft. The actuator operates in response to a 2 to 10 VDC, or with the addition of a 500Ω resistor, a 4 to 20 mA control input from an electronic controller or positioner. A 2 to 10 VDC feedback signal is provided for position indication.
Typical Specification
Spring return control damper actuators shall be direct coupled type which require no crank arm and linkage and be capable of direct mounting to a shaft up to a 3/4" diameter and center on a 1/2" shaft (default). Actuator shall deliver a minimum output torque of 35 in-lbs. The actuator must provide modulating damper control in response to a 2 to 10 VDC or, with the addition of a 500Ω resistor, a 4 to 20 mA control input from an electronic controller. Actuators shall use a brushless DC motor controlled by a microprocessor and be protected from overload at all angles of rotation. Run time shall be constant, and independent of torque. A 2 to 10 feedback signal shall be provided for position feedback. The actuator must be designed so that they may be used for either clockwise or counter clockwise failsafe operation. Actuators shall be cULus listed, have a 5 year warranty, and be manufactured under ISO 9001 International Quality Control Standards. Actuators shall be as manufactured by Belimo.
CP65 Warning
⚠ WARNING: For Belimo Products sold in California, these Products do or may contain chemicals which are known to the State of California to cause cancer and or birth defects or other reproductive harms. For more information see www.p65warnings.ca.gov.

Installation instructions Download: Installation instructions

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