The Belimo CMB120-3 is a compact non-spring-return mini damper actuator delivering 18 in-lb [2 Nm] of torque with on/off and floating-point control on AC 100-240 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.
Specifications sourced from the official Belimo CMB120-3 technical data sheet (rev 2025-10-06).
Overview
Belimo CM-Series actuators are Belimo's most compact non-spring-return drives, made for small zone, VAV and terminal-unit dampers. The CMB120-3 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. Two-position on/off and 3-wire floating-point control position the damper from a controller, relay or switch.
Best for
- Compact zone, VAV and terminal-unit damper control
- 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)
- Line-voltage systems (AC 100-240 V)
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..
On/Off & Floating Point
Accepts two-position on/off or 3-wire floating-point control from a controller, relay or switch.
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.
Line-Voltage Power
Runs directly on AC 100-240 V — no separate 24 V transformer required.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Belimo |
| Part Number | CMB120-3 |
| Actuator Type | Non-Spring-Return (Non Fail-Safe) Mini Damper Actuator |
| Motor | Brushless DC (sensorless) |
| Nominal Voltage | AC 100-240 V |
| Nominal Frequency | 50/60 Hz |
| Power Consumption (Running) | 1.5 W |
| Transformer Sizing | 3.5 VA |
| Torque | 18 in-lb [2 Nm] |
| Control Signal | On/Off and Floating Point (3-wire) |
| 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) |
| 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 | 0.61 lb [0.28 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for the CMB120-3, 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 CMB120-3?
The Belimo CMB120-3 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 on/off and floating-point control on AC 100-240 V power, runs on a quiet brushless DC motor, and holds its last position on loss of power.
Is the CMB120-3 a spring-return (fail-safe) actuator?
No. The CMB120-3 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 CMB120-3 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 CMB120-3 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.
How do you manually position the CMB120-3?
The CMB120-3 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.
What voltage does the CMB120-3 run on?
The CMB120-3 is a line-voltage actuator running on AC 100-240 V, so no separate 24 V control transformer is required.
Is the Belimo CMB120-3 available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the CMB120-3. 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:
- On/Off
- Voltage:
- Line Voltage (100-240 VAC)
- Series:
- CMB
