Damper Actuator, 35 in-lb [4 Nm], Spring return, AC/DC 24 V, On/Off, 1 x SPDT
Fail-safe position
Weight 3.4 lbs

35 in-lb


AC/DC 24 V

Auxiliary Switch


Actuator Type

Spring return

Control type



Torque motor
35 in-lb [4 Nm]
Power consumption in operation
5 W
Power consumption in rest position
2.5 W
Transformer sizing
7 VA (class 2 power source)
Ambient humidity
5...95% r.H. non-condensing
Housing material
zinc coated steel
Electrical Connection
(2) 18 GA appliance cables with 1/2" conduit connectors, 3 ft [1 m],
Auxiliary switch
1 x SPDT, 3A resistive (0.5A inductive) @ 250 VAC, adjustable 0...95°
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]
direction of rotation motor
reversible with built-in switch
Overload Protection
electronic throughout 0° to 95° rotation
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
Emergency control function
Spring Return
Product family
Damper Actuator
direction of rotation spring-return
reversible with cw/ccw mounting
Noise level, motor
<50 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)
40...75 sec
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
Auxiliary Switch
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 actuator may be stalled anywhere in its normal rotation without the need of mechanical end switches. Power consumption is reduced in holding mode. The LF24-S US version is provided with one built in auxiliary switch. This SPDT switch is provided for safety interfacing or signaling, for example, for fan start-up. The switching function is adjustable between 0° and 95°. The auxiliary switch in the LF24-S US is double insulated so an electrical ground connection is not necessary.
For On/Off, fail-safe control of dampers in HVAC systems. Actuator sizing should be done in accordance with the damper manufacturer’s 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 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.
Typical Specification
On/Off spring return 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 be designed so that they may be used for either clockwise or counter clockwise failsafe operation. Actuators shall be protected from overload at all angles of rotation. If required, one SPDT auxiliary switch shall be provided with one switch having the capability of being adjustable. Actuators with auxiliary switch must be constructed to meet the requirement for Double Insulation so an electrical ground connection is not required to meet agency listings. 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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