The Belimo TFLB24 is a compact spring-return (fail-safe) damper actuator delivering 22 in-lb [2.5 Nm] of torque with on/off (two-position) 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 the low-noise version of the standard TFB24 for small commercial HVAC dampers that must fail safe. It runs at under 40 dB(A) for quiet operation, with a slower (under 75-second) fail-safe return as a result.
Specifications sourced from the official Belimo TFLB24 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 TFLB24 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 75 seconds; the fail-safe direction is reversible by CW/CCW mounting. This TFLB model is the low-noise version of the TFB: it operates at under 40 dB(A), with a slower fail-safe return (under 75 seconds) as a trade-off. Two-position on/off control drives the damper, and the spring returns it on signal or power loss.
Best for
- Noise-sensitive spaces needing quiet operation (under 40 dB(A))
- Small commercial HVAC dampers needing fail-safe (spring-return) operation
- 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.
On/Off Control
Accepts two-position on/off control from a controller, relay or switch.
Reversible Fail-Safe Direction
The spring-return (fail-safe) direction is selectable clockwise or counterclockwise by mounting orientation.
Low-Noise Operation
Runs at under 40 dB(A) in both the motor and fail-safe directions — the low-noise version of the TFB for sound-sensitive spaces. The spring returns more slowly (under 75 seconds) as a trade-off.
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 | TFLB24 |
| Actuator Type | Spring-Return (Fail-Safe) Damper Actuator |
| Nominal Voltage | AC/DC 24 V |
| Nominal Frequency | 50/60 Hz |
| Power Consumption (Running) | 2.5 W |
| Torque (Motor & Spring) | 22 in-lb [2.5 Nm] (minimum) |
| Control Signal | On/Off (two-position) |
| 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) | 75 s |
| Spring Return Time | < 75 s 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 |
| Noise Level | < 40 dB(A) (low-noise, motor & fail-safe) |
| 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 | 1.6 lb [0.73 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for mounting, linkage, signaling and powering the TFLB24, 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 TFLB24?
The Belimo TFLB24 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 on/off (two-position) control on AC/DC 24 V power, and on power loss its spring drives the damper to a fail-safe position in under 75 seconds.
Is the TFLB24 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 TFLB24 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 TFLB24 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 TFLB24 use?
It uses on/off (two-position) control. Two-position on/off control is driven from a controller, relay or switch.
What is the difference between the TFLB24 and the TFB24?
The TFLB24 is the low-noise version of the TFB24. Both are 22 in-lb, AC/DC 24 V, on/off spring-return actuators, but the TFLB24 is built for quieter operation (under 40 dB(A)). As a trade-off its fail-safe spring return is slower — under 75 seconds, versus under 25 seconds on the TFB. If your job specifies a required spring-return time, confirm the published spec before treating them as equals.
Does the TFLB24 have a manual override?
No. Like other compact spring-return actuators, the TFLB24 has no manual override — the spring sets the fail-safe position and the motor drives the powered direction.
Is the Belimo TFLB24 available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the TFLB24. 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:
- On/Off
- Voltage:
- 24 VAC/DC
- Auxiliary Switch:
- No
- Series:
- TF
- Acoustic:
- Low-Noise (<40 dB(A))
