The Belimo LMX24-SR-F is a compact non-spring-return damper actuator delivering 45 in-lb [5 Nm] of torque with modulating 2-10 VDC control on AC/DC 24 V power. It couples via a form-fit 8 x 8 mm square coupler and is non-fail-safe, with no spring return, making it part of Belimo's configurable LMX platform for small to mid-size commercial HVAC dampers. A square form-fit coupler lets it drive square jackshafts directly.
Specifications sourced from the official Belimo LMX24-SR-F technical data sheet (rev 2026-03-18).
Overview
Belimo LM-Series actuators are compact non-spring-return drives for small and mid-size commercial HVAC dampers — they position the damper under power and have no spring-return fail-safe function. The LMX24-SR-F produces 45 in-lb [5 Nm] and mounts directly to form fit 8 x 8 mm (square jackshaft coupler). A 2-10 VDC (or 4-20 mA with the ZG-R01 resistor) signal modulates the damper, with 2-10 VDC position feedback.
Best for
- Modulating damper control without fail-safe return
- Small to mid-size damper and louver positioning (45 in-lb)
- Form-fit 8 x 8 mm square jackshaft mount
- Square jackshaft / form-fit coupling
Key Features
Non-Spring-Return Design
No fail-safe spring return. Belimo does not publish a defined position on loss of power for this model; specify a spring-return actuator where a fail-safe position is required.
45 in-lb Torque
Sized for small and mid-size dampers; couples via a form-fit 8 x 8 mm square coupler.
Modulating 2-10 VDC
Accepts a 2-10 VDC (or 4-20 mA with ZG-R01) signal with 2-10 VDC position feedback.
Square Form-Fit Coupler
Couples directly to square jackshafts with a form-fit adaptor — no round-shaft clamp required.
cULus Listed & Quiet
cULus listed, ISO 9001 built, UL 2043 plenum-rated for long, maintenance-free service.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Belimo |
| Part Number | LMX24-SR-F |
| Actuator Type | Non-Spring-Return (Non Fail-Safe) Damper Actuator |
| Nominal Voltage | AC/DC 24 V |
| Nominal Frequency | 50/60 Hz |
| Power Consumption (Running) | 1.5 W |
| Transformer Sizing | 3 VA |
| Torque | 45 in-lb [5 Nm] |
| 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) |
| Mechanical Interface | Form fit 8 x 8 mm (square jackshaft coupler) — per SKU technical data; general LM application text in the same datasheet describes the universal clamp and does not apply to this -F variant |
| Angle of Rotation | Max. 95° (adjustable mechanical stop) |
| Running Time (Motor) | 95 s / 90° |
| Running Time Note | constant, independent of load |
| Variable Running Time | 35, 45, 60, 150 s |
| Behavior on Power Loss | Non fail-safe — no fail-safe spring return function |
| Shaft Coupling | Square form-fit coupler (for square / jackshaft shafts) |
| Manual Override | External push button |
| Direction of Motion | Selectable with 0/1 switch |
| Electrical Connection | 18 AWG plenum cable, 3 ft [1 m], 1/2 in. NPT conduit connector |
| Overload Protection | Electronic, full 0-95° rotation |
| Power Source | UL Class 2 Supply |
| Enclosure Rating | NEMA 2 / UL Type 2 |
| Ingress Protection | IP54 — stated on the datasheet for the cable and conduit connector |
| 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 | 0.89 lb [0.41 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for mounting, linkage, signaling and powering the LMX24-SR-F, drawn from the actuator datasheet. All are stocked by ZOT Supply as an authorized Belimo distributor.
Mounting & Linkage
Electrical Add-Ons
Enclosures & Weather Shields
Frequently Asked Questions
What is the Belimo LMX24-SR-F?
The Belimo LMX24-SR-F is a compact non-spring-return (non-fail-safe) damper actuator for commercial HVAC. It produces 45 in-lb [5 Nm] of torque, uses modulating 2-10 VDC control on AC/DC 24 V power. It is non-fail-safe: Belimo does not publish a defined position on loss of power for this model. Its housing is rated NEMA 2.
Is the LMX24-SR-F a spring-return (fail-safe) actuator?
No. The LMX24-SR-F is non-spring-return: it has no fail-safe spring, so it will not drive to a predetermined position when power is lost. Where a defined position on power loss is required, select a spring-return actuator sized to the damper manufacturer's specifications.
What happens to the LMX24-SR-F when power is lost?
There is no spring return, so the actuator does not drive itself to a fail-safe position. Belimo's datasheet for this model does not publish a defined power-loss position; if your sequence depends on a specific position during a power failure, specify a spring-return actuator.
What shaft sizes does the LMX24-SR-F fit?
It couples via a form-fit 8 x 8 mm square coupler. A square form-fit coupler is included for square jackshafts.
What control signal does the LMX24-SR-F 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.
What is the running time of the LMX24-SR-F?
Motor running time is 95 s / 90°. Belimo also publishes variable running-time values of 35, 45, 60, 150 s.
What does the -F suffix mean on the LMX24-SR-F?
The -F denotes a square form-fit mechanical coupler, letting the actuator drive square jackshafts directly without a separate round-shaft clamp.
Is the Belimo LMX24-SR-F available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the LMX24-SR-F. Every unit ships factory new with Belimo's full 5-year warranty and application support.
- Actuator Type:
- Non-Fail-Safe
- Torque:
- 45 in-lb
- Control Signal:
- Modulating
- Voltage:
- 24 VAC/DC
- Auxiliary Switch:
- No
- Series:
- LM
- Feedback Signal:
- 2-10 VDC
