Fire & Smoke Actuator, 70 in-lb [8 Nm] from 32…350°F [0…177°C], Spring return, AC/DC 24 V, On/Off

Fail-safe position
Weight 5.8 lbs
Actuator Type

Spring return



Control type


maintenance free
70 in-lb
Torque motor
70 in-lb [8 Nm] from 32...350°F [0...177°C]
Torque note
from 32...350°F [0...177°C]
Power consumption in operation
27 VA
Power consumption in rest position
3 W, 6.5 VA, End stop 55 VA, 2.5 A slow blow fuse *
Transformer sizing
40 VA (class 2 power source)
Ambient humidity
5...95% r.H. non-condensing
Housing material
zinc coated steel
Electrical Connection
18 GA, 3 ft [1 m], 2 color coded wires
Angle of rotation
Noise level, motor
45 dB (A) motor, 62 dB (A) spring, inaudible holding 
Position indication
visual indicator, 0° to 95° (0° is full spring return position)
Ambient temperature
32...122°F [0...50°C]
Non-operating temperature
-40...176°F [-40...80°C]
direction of rotation spring-return
reversible with cw/ccw mounting
Overload Protection
electronic throughout 0° to 95° rotation
Electrical Protection
actuators are double insulated
Quality Standard
ISO 9001
Degree of Protection
IP40, NEMA 1
steel, permanently lubricated
direction of rotation motor
reversible with CW/CCW mounting
Data sheet type
Product Features
Fire & Smoke damper actuator
Nominal voltage
AC/DC 24 V
Nominal voltage AC
24 V
Nominal voltage DC
24 V
Nominal voltage frequency
50/60 Hz
Power Supply
24 VAC, ±20%, 50/60 Hz, 24 VDC, 0% / +50%
Power supply tolerance AC
Power supply tolerance DC
0% / +50%
Mechanical accessories
AF-P|IND-AF2|K4-1 US|KH-AF-1 US|KH-AF|SH8|ZDB-AF2 US|ZG-100|ZG-101|ZG-AF US|ZG-AF108|ZG-DC1|ZG-DC2|ZS-100|ZS-150|ZS-260|ZS-300
Electrical accessories
Family Series
FSNF Series
Shaft Diameter
1/2" to 1.05" round, centers on 1/2" and 3/4" with insert, 1.05" without insert
Running Time (Motor)
15 sec between 32...350°F [0...177°C], <15 sec at rated voltage & torque
Running time motor note
between 32...350°F [0...177°C], <15 sec at rated voltage & torque
Running time (Fail-Safe)
15 seconds
Running Time (Fail-Safe)
15 sec
Emergency control function
Spring Return
Degree of protection IEC/EN
Degree of protection NEMA/UL
The type FSNF spring-return actuator is intended for the operation of smoke and combination fire and smoke dampers in ventilation and air-conditioning systems. The actuator will meet requirements of UL555 and UL555S when tested as an assembly with the damper and will meet requirements of UBC for 15 second opening and closing at 350°F. Square footage of damper operated will depend on make and model and the temperature required. IMPORTANT 24VDC NOTE: The FSNF24 & -S models will not operate below 24VDC. A filtered and regulated power supply must be used.
Mounting of the actuator to the damper axle shaft or jackshaft (3/8” to 1.05”) is via a cold-weld clamp. Teeth in the clamp and V-bolt dig into the metal of both solid and hollow shafts maintaining a perfect connection. The specially designed clamp will not crush hollow shafts. The bottom end of the actuator is held by an anti-rotation strap or by a stud provided by the damper manufacturer. The actuator is mounted in its fail safe position with the damper blade(s) closed. Upon applying power, the actuator drives the damper to the open position. The internal spring is tensioned at the same time. If the power supply is interrupted, the spring moves the damper back to its fail-safe position.
Typical Specification
All smoke and combination fire and smoke dampers shall be provided with Belimo FSTF, FSLF, FSNF, or FSAF actuators. All substitutions must be approved before submission of bid. Damper and actuator shall have UL 555S Listing for 250°F (350°F). Actuator shall have been tested to UL 2043 per requirements of IMC 602.2 and NEC 300.22 (c). Where position indication is required -S models with auxiliary switches or damper blade switches will be provided per code requirements.
Agency Listing
cULus listed to UL873 and CAN/CSA C22.2 No.24, UL 2043 Listed for air plenum installation per NEC 300.22 and IMC Section 602 NYC Department of Buildings MEA 197-07-M.California State Fire Marshal Listing 3210-1593:101.
Safety Notes
* Neither UL nor Belimo require local over-current protection. The FSNF actuators draw higher peak current when driving against any type of stop. If used, this requires the value of a local fuse or breaker to be increased to avoid nuisance opening or tripping. A 2.5 amp slow blow should be used for 24VAC. A 0.5 amp slow blow should be used for 120 VAC. A 0.25 amp slow blow should be used for 230V and a 0.3 amp slow blow for 208 VAC. Transformers: Note that while a 24V 100VA transformer would handle 2 actuators, a 4 A breaker or plug fuse is insufficient. A 5 amp slow blow would be required. Belimo Fire & Smoke actuators have passed the AMCA 520 and UL 555S Long Term Holding test. No special cycling is required during prolonged periods when actuator is driven open and held there. Periodic testing of dampers and actuators per local codes and NFPA 80 and NFPA 105 are required. The actuator contains no components which the user can replace or repair. A 1/2" threaded connector is standard. FSNFxx-FC models have a 3/8" Flex Connector. Other than the connector, these actuators are identical to the conduit connector version.
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.

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