The Belimo TFB24-MFT-S is a compact spring-return (fail-safe) damper actuator delivering 22 in-lb [2.5 Nm] of torque with field-programmable MFT control that ships set for 2-10 VDC by default 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. A built-in SPDT auxiliary switch signals damper position or interlocks equipment.
Specifications sourced from the official Belimo TFB24-MFT-S technical data sheet (rev 2023-03-10).
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-MFT-S 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. It ships set for 2-10 VDC modulating control, and Multi-Function Technology lets you field-select other signals, ranges and feedback under one part number.
Best for
- Modulating control with field-selectable signal (2-10 VDC default)
- Compact zone, VAV and terminal-unit damper control (22 in-lb)
- Outdoor-air and exhaust dampers that must fail safe
- End-position signaling or interlock (1x SPDT)
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.
MFT — 2-10 VDC by Default
Ships set for 2-10 VDC modulating control. Field-select other signals and ranges under one part number.
Reversible Fail-Safe Direction
The spring-return (fail-safe) direction is selectable clockwise or counterclockwise by mounting orientation.
Built-In SPDT Aux Switch
One SPDT auxiliary switch (1 mA-3 A) signals damper end position or interlocks other equipment.
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-MFT-S |
| 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 | Modulating, field-programmable (MFT) — ships set for 2-10 VDC by default |
| Selectable Modes | 2-10 VDC (default), variable VDC, On/Off, Floating Point, PWM |
| Position Feedback (U) | 2-10 VDC default (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) | 150 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 |
| Auxiliary Switch | 1x SPDT, 1 mA-3 A (0.5 A inductive), DC 5 V-AC 250 V |
| 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-MFT-S, 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-MFT-S?
The Belimo TFB24-MFT-S 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 field-programmable MFT control (set for 2-10 VDC by default) 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-MFT-S 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-MFT-S 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-MFT-S 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-MFT-S use?
It uses field-programmable MFT control (set for 2-10 VDC by default). Because it is MFT, you can field-select other modes (variable VDC, on/off, floating point, PWM) without changing the part number.
Does the TFB24-MFT-S have an auxiliary switch?
Yes. It has one SPDT auxiliary switch (rated 1 mA to 3 A at up to 250 V) for end-position signaling or interlocking other equipment.
Is the TFB24-MFT-S the same as the SR (2-10 VDC) version?
Functionally yes — it ships set for 2-10 VDC modulating control, identical to the SR model. MFT simply lets you field-select other signals and ranges, so one part number covers many specifications.
Does the TFB24-MFT-S have a manual override?
No. Like other compact spring-return actuators, the TFB24-MFT-S has no manual override — the spring sets the fail-safe position and the motor drives the powered direction.
Is the Belimo TFB24-MFT-S available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the TFB24-MFT-S. Every unit ships factory new with Belimo's full 5-year warranty and application support.
- Actuator Type:
- Spring-Return (Fail-Safe)
- Torque:
- 22 in-lb
- Control Signal:
- Programmable (MFT)
- Voltage:
- 24 VAC/DC
- Auxiliary Switch:
- 1x SPDT
- Series:
- TFB
- Feedback Signal:
- 2-10 VDC
