The Belimo TFB24-SR is a compact spring-return (fail-safe) damper actuator delivering 22 in-lb [2.5 Nm] of torque with modulating 2-10 VDC control on AC/DC 24 V power. As Belimo's smallest spring-return class, it direct-couples to round damper shafts from 1/4 in. to 1/2 in. and, on loss of power, its internal spring returns the damper to a fail-safe position in under 25 seconds, making it a member of the TFB platform for small commercial HVAC dampers that must fail safe.
Specifications sourced from the official Belimo TFB24-SR technical data sheet (rev 2023-08-11).
Overview
Belimo TF-Series actuators are Belimo's smallest spring-return drives, sized for small commercial HVAC control dampers that require fail-safe operation. The TFB24-SR produces 22 in-lb [2.5 Nm] and mounts directly to round damper shafts from 1/4 in. to 1/2 in. with its universal clamp. On power loss the spring returns the damper to its fail-safe position in under 25 seconds; the fail-safe direction is reversible by CW/CCW mounting. A 2-10 VDC signal (or 4-20 mA with the ZG-R01 resistor) modulates the damper with 2-10 VDC position feedback; the spring provides fail-safe return.
Best for
- Modulating small-damper control with fail-safe return
- Compact zone, VAV and terminal-unit damper control (22 in-lb)
- Outdoor-air and exhaust dampers that must fail safe
Key Features
Spring-Return Fail-Safe
A mechanical spring drives the damper to a safe position on power or signal loss (under 25 seconds) — no external power needed to fail safe.
Smallest 22 in-lb Class
Belimo's most compact spring-return actuator; direct-couples to round damper shafts from 1/4 in. to 1/2 in. for small dampers.
Modulating 2-10 VDC
Accepts a 2-10 VDC (or 4-20 mA with ZG-R01) signal with 2-10 VDC position feedback.
Reversible Fail-Safe Direction
The spring-return (fail-safe) direction is selectable clockwise or counterclockwise by mounting orientation.
cULus Listed & Quiet
Double-insulated (Class 2), cULus listed, ISO 9001 built and UL 2043 plenum-rated for long, maintenance-free service.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Belimo |
| Part Number | TFB24-SR |
| Actuator Type | Spring-Return (Fail-Safe) Damper Actuator |
| Nominal Voltage | AC/DC 24 V |
| Nominal Frequency | 50/60 Hz |
| Power Consumption (Running) | 2 W |
| Torque (Motor & Spring) | 22 in-lb [2.5 Nm] (minimum) |
| Control Signal | Modulating |
| Operating Range (Y) | 2-10 VDC (4-20 mA with ZG-R01 resistor) |
| Position Feedback (U) | 2-10 VDC (max. 0.5 mA) |
| Shaft Range | 1/4 in. to 1/2 in. [6.4-12.7 mm] via universal clamp (1/2 in. self-centering) |
| Angle of Rotation | 95° (adjustable mechanical stops) |
| Running Time (Motor) | 95 s / |
| Spring Return Time | < 25 s (< 60 s below -22°F) for fail-safe |
| Behavior on Power Loss | Spring returns damper to fail-safe position |
| Fail-Safe Direction | Reversible (CW/CCW) by mounting orientation |
| Electrical Connection | 18 GA appliance cable, 3 ft [1 m], 1/2" NPT conduit connector |
| Overload Protection | Electronic, full 0-95° rotation |
| Electrical Protection | Double insulated (Class 2) |
| Enclosure Rating | NEMA 2 / UL Type 2 |
| Ambient Temperature | -22 to 122°F [-30 to 50°C] |
| Agency Listing | cULus (UL60730-1A/-2-14, CAN/CSA) |
| Quality Standard | ISO 9001 |
| Plenum Rated | UL 2043 (suitable for air plenums) |
| Weight | 1.8 lb [0.83 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for mounting, linkage, signaling and powering the TFB24-SR, drawn from the TF actuator datasheet. All are stocked by ZOT Supply as an authorized Belimo distributor.
Mounting & Linkage
Electrical Add-Ons
Frequently Asked Questions
What is the Belimo TFB24-SR?
The Belimo TFB24-SR is Belimo's smallest spring-return (fail-safe) damper actuator, for small commercial HVAC dampers. It produces 22 in-lb [2.5 Nm] of torque, uses modulating 2-10 VDC control on AC/DC 24 V power, and on power loss its spring drives the damper to a fail-safe position in under 25 seconds.
Is the TFB24-SR a spring-return (fail-safe) actuator?
Yes. A mechanical spring drives the damper to its fail-safe position when power or the control signal is lost — no external power is needed to fail safe.
How much torque does the TFB24-SR provide?
It delivers 22 in-lb [2.5 Nm] of torque. TF is Belimo's smallest spring-return class, sized for compact zone, VAV and terminal-unit dampers.
What shaft sizes does the TFB24-SR fit?
It direct-couples to round damper shafts from 1/4 in. to 1/2 in. using its universal clamp, self-centering at 1/2 in. A crank arm (KH-TF US) and brackets are available for off-shaft mounting.
What control signal does the TFB24-SR use?
It uses modulating 2-10 VDC control. The 2-10 VDC input also accepts 4-20 mA with the ZG-R01 resistor and provides 2-10 VDC feedback.
Does the TFB24-SR have a manual override?
No. Like other compact spring-return actuators, the TFB24-SR has no manual override — the spring sets the fail-safe position and the motor drives the powered direction.
Is the Belimo TFB24-SR available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the TFB24-SR. Every unit ships factory new with Belimo's full 5-year warranty and application support.
- Actuator Type:
- Fail-Safe
- Torque:
- 22 in-lb
- Control Signal:
- Modulating
- Voltage:
- 24 VAC/DC
- Auxiliary Switch:
- No
- Series:
- TF
- Feedback Signal:
- 2-10 VDC
