The Belimo CMB24-SR-L is a compact non-spring-return mini damper actuator delivering 18 in-lb [2 Nm] of torque with modulating 2-10 VDC control (with 2-10 VDC position feedback) on AC/DC 24 V power. Built on a quiet brushless DC motor, it direct-couples to round or square damper shafts from 1/4 in. to 1/2 in. with a universal spindle clamp or form-fit and holds its last position on loss of power (non-fail-safe, no spring return), making it ideal for small zone, terminal-unit and VAV dampers in commercial HVAC. Its motor is factory-set for counterclockwise (left-hand) default rotation (the -L suffix).
Specifications sourced from the official Belimo CMB24-SR-L technical data sheet (rev 2026-06-03).
Overview
Belimo CM-Series actuators are Belimo's most compact non-spring-return drives, made for small zone, VAV and terminal-unit dampers. The CMB24-SR-L produces 18 in-lb [2 Nm] and mounts directly to round or square damper shafts from 1/4 in. to 1/2 in. with a universal spindle clamp or form-fit coupling, secured by the supplied anti-rotation bracket. A quiet, overload-proof brushless DC motor drives 90° in about 35 seconds and holds the last commanded position when power is removed (there is no spring-return fail-safe); manual positioning is possible by disengaging the gear train with a magnet. A 2-10 VDC signal (or 4-20 mA with the ZG-R01 resistor) modulates the damper, with 2-10 VDC position feedback. This unit is the -L version, factory-set for counterclockwise (left-hand) default rotation.
Best for
- Modulating zone / VAV damper control without fail-safe return
- Small damper / louver positioning (18 in-lb)
- Tight spaces where a low-profile mini actuator is needed
- Non-spring-return applications (no fail-safe required)
- Counterclockwise (left-hand) default rotation
Key Features
Compact Non-Spring-Return
Belimo's smallest damper actuator class. Holds the last commanded position when power is removed (non-fail-safe) — lower cost and draw than a spring-return where fail-safe is not required.
18 in-lb Torque
Sized for small zone, VAV and terminal-unit dampers; direct-couples to round or square damper shafts from 1/4 in. to 1/2 in..
Modulating 2-10 VDC
Accepts a 2-10 VDC (or 4-20 mA with ZG-R01) signal with 2-10 VDC position feedback.
CCW / Left-Hand Rotation
Factory-set for counterclockwise (left-hand) default rotation (the -L configuration) for correct damper orientation out of the box.
Quiet Brushless DC Motor
An overload-proof brushless DC motor needs no limit switches, runs quietly, and stops automatically at the end stops; power draw drops in holding mode.
Magnetic Manual Override
Disengage the gear train with a magnet to position the damper by hand — no tools or cranks required.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Belimo |
| Part Number | CMB24-SR-L |
| Actuator Type | Non-Spring-Return (Non Fail-Safe) Mini Damper Actuator |
| Motor | Brushless DC (sensorless) |
| Nominal Voltage | AC/DC 24 V |
| Nominal Frequency | 50/60 Hz |
| Power Consumption (Running) | 1.5 W |
| Transformer Sizing | 1.5 VA |
| Torque | 18 in-lb [2 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 1/2 in. (universal spindle clamp or form-fit) |
| Angle of Rotation | Max. 95° (adjustable mechanical stops) |
| Running Time (Motor) | 35 s / 90° |
| Behavior on Power Loss | Holds last position (non-spring-return) |
| Default Rotation Direction | Counterclockwise (left-hand), -L |
| Manual Override | Gear disengagement via magnet (Z-MA) |
| Mounting | Direct shaft mount; anti-rotation bracket supplied |
| Electrical Connection | 18 AWG plenum cable, 3 ft [1 m], 1/2" NPT 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) |
| Housing Material | UL94-5VA |
| Quality Standard | ISO 9001 |
| Plenum Rated | UL 2043 (suitable for air plenums) |
| Weight | 0.59 lb [0.27 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for the CMB24-SR-L, drawn from the CM actuator datasheet. All are stocked by ZOT Supply as an authorized Belimo distributor.
Mounting & Linkage
Tools & Electrical
Frequently Asked Questions
What is the Belimo CMB24-SR-L?
The Belimo CMB24-SR-L is a compact non-spring-return (non-fail-safe) mini damper actuator for commercial HVAC. It produces 18 in-lb [2 Nm] of torque, uses modulating 2-10 VDC control on AC/DC 24 V power, runs on a quiet brushless DC motor, and holds its last position on loss of power.
Is the CMB24-SR-L a spring-return (fail-safe) actuator?
No. The CMB24-SR-L is non-spring-return: on power loss it holds its last position rather than driving to a fail-safe position. For fail-safe operation choose a spring-return Belimo actuator instead.
What shaft sizes does the CMB24-SR-L fit?
It direct-couples to round or square damper shafts from 1/4 in. to 1/2 in. using a universal spindle clamp or form-fit coupling, and ships with an anti-rotation bracket.
What control signal does the CMB24-SR-L 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 difference between the CMB24-SR-L and CMB24-SR-R?
They are the same modulating mini actuator; the suffix sets the factory default rotation direction. The -L turns counterclockwise (left-hand) and the -R turns clockwise (right-hand) as the control signal increases. Pick the one that matches your damper's open direction.
How do you manually position the CMB24-SR-L?
The CMB24-SR-L has no manual crank; instead you disengage the gear train with a magnet (Belimo Z-MA) to turn the damper by hand, then release to re-engage.
Is the Belimo CMB24-SR-L available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the CMB24-SR-L. Every unit ships factory new with Belimo's full 5-year warranty and application support.
- Actuator Type:
- Non-Spring-Return
- Torque:
- 18 in-lb
- Control Signal:
- Modulating
- Voltage:
- 24 VAC/DC
- Series:
- CMB
- Rotation Direction:
- Counterclockwise (-L)
- Feedback Signal:
- 2-10 VDC
