The Belimo LMB24-SR 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 direct-couples to round or square damper shafts from 1/4 in. to 5/8 in. (up to 3/4 in. with an accessory clamp) and is non-fail-safe, with no spring return, making it a proven member of the LMB platform for small to mid-size commercial HVAC dampers.
Specifications sourced from the official Belimo LMB24-SR technical data sheet (rev 2025-12-23).
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 LMB24-SR produces 45 in-lb [5 Nm] and mounts directly to round or square damper shafts from 1/4 in. to 5/8 in. (up to 3/4 in. with an accessory clamp). 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)
- Direct shaft mount, 1/4-5/8 in. (to 3/4 in. with accessory clamp)
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; direct-couples to round or square damper shafts from 1/4 in. to 5/8 in. (up to 3/4 in. with an accessory clamp).
Modulating 2-10 VDC
Accepts a 2-10 VDC (or 4-20 mA with ZG-R01) signal with 2-10 VDC position feedback.
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 | LMB24-SR |
| 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) |
| Shaft Range | 1/4 in. to 5/8 in. (to 3/4 in. with accessory clamp) |
| Angle of Rotation | Max. 95° (adjustable mechanical stop) |
| Running Time (Motor) | 95 s / 90° |
| Running Time Note | constant, independent of load |
| Behavior on Power Loss | Non fail-safe — no fail-safe spring return function |
| 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 | 1.3 lb [0.59 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for mounting, linkage, signaling and powering the LMB24-SR, 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 LMB24-SR?
The Belimo LMB24-SR 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 LMB24-SR a spring-return (fail-safe) actuator?
No. The LMB24-SR 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 LMB24-SR 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 LMB24-SR fit?
It direct-couples to round or square damper shafts from 1/4 in. to 5/8 in. (up to 3/4 in. with an accessory clamp) using its universal clamp.
What control signal does the LMB24-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.
What is the running time of the LMB24-SR?
Motor running time is 95 s / 90°.
Is the Belimo LMB24-SR available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the LMB24-SR. 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
