The Belimo LMB24-3-S is a compact non-spring-return damper actuator delivering 45 in-lb [5 Nm] of torque with on/off and floating-point 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 holds its last position on loss of power (it 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. A built-in SPDT auxiliary switch signals damper position or interlocks equipment.
Specifications sourced from the official Belimo LMB24-3-S 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 hold the last commanded position when power is removed (there is no spring-return fail-safe). The LMB24-3-S 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). Two-position on/off and 3-wire floating-point control position the damper from a controller or switch.
Best for
- Compact non-spring-return damper control where fail-safe return is not required
- 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)
- End-position signaling or equipment interlock
Key Features
Non-Spring-Return Design
Holds the last commanded position when power is removed (non-fail-safe). Lower cost and power draw than a spring-return actuator where fail-safe operation is not 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).
On/Off & Floating Point
Accepts two-position on/off or 3-wire floating-point control from a controller, relay or switch.
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, UL 2043 plenum-rated for long, maintenance-free service.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Belimo |
| Part Number | LMB24-3-S |
| 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 | 2.5 VA |
| Torque | 45 in-lb [5 Nm] |
| Control Signal | On/Off and Floating Point (3-wire) |
| 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° |
| Behavior on Power Loss | Holds last position (non-spring-return) |
| Auxiliary Switch | 1x SPDT, 1 mA-3 A (0.5 A inductive), DC 5 V-AC 250 V |
| Manual Override | External push button (self-locking gear) |
| Direction of Motion | Selectable with 0/1 switch |
| Electrical Connection | 18 AWG plenum 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 | 0.86 lb [0.39 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for mounting, linkage, signaling and powering the LMB24-3-S, 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 LMB24-3-S?
The Belimo LMB24-3-S is a compact non-spring-return (non-fail-safe) damper actuator for commercial HVAC. It produces 45 in-lb [5 Nm] of torque, uses on/off and floating-point control on AC/DC 24 V power, and holds its last position on loss of power. Its housing is rated NEMA 2.
Is the LMB24-3-S a spring-return (fail-safe) actuator?
No. The LMB24-3-S is non-spring-return: when power is lost it holds its last commanded position rather than driving to a fail-safe position. If you need fail-safe operation, choose a spring-return Belimo LF-Series actuator instead.
What happens to the LMB24-3-S when power is lost?
It stays put. A non-spring-return actuator maintains its last position when power is removed and resumes from there when power returns.
What shaft sizes does the LMB24-3-S 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 LMB24-3-S use?
It uses on/off and floating-point control. On/Off and 3-wire floating-point control are driven from a controller, relay or switch.
What is the running time of the LMB24-3-S?
Motor running time is about 95 s / 90° for 90 degrees of travel.
Does the LMB24-3-S have an auxiliary switch?
Yes. It has one built-in SPDT auxiliary switch (rated 1 mA to 3 A) for end-position signaling or interlocking other equipment.
Is the Belimo LMB24-3-S available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the LMB24-3-S. 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:
- On/Off
- Voltage:
- 24 VAC/DC
- Auxiliary Switch:
- 1x SPDT
- Series:
- LM
