The Belimo CQKB24-SR-LL Fail-Safe Actuator is a compact, high-precision solution designed for HVAC and building automation applications where safety and reliability are critical. Featuring an integrated spring return mechanism, the actuator automatically drives the connected damper to a predefined safe position when power is lost, ensuring controlled system behaviour during faults or emergencies.

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Nominal voltage	AC/DC 24 V
Nominal voltage frequency	50/60 Hz
Nominal voltage range	AC 19.2...28.8 V / DC 21.6...28.8 V
Power consumption in operation	2.5 W
Power consumption in rest position	0.5 W
Transformer sizing	5 VA
Electrical Connection	22 AWG plenum cable, 1 m, with 1/2" NPT conduit connector
Overload Protection	Electronic thoughout 0...90° rotation
Electrical Protection	Actuators are double insulated

The Belimo CQKB24-SR-LL fail-safe actuator delivers accurate modulating control while safeguarding your system during power loss. Designed for compact HVAC and ventilation applications, it provides smooth, proportional airflow management in normal operation and instant, predictable positioning in fault conditions. This combination of control and safety makes it ideal for environments where space is limited and reliability is non-negotiable—ensuring airflow remains stable, efficient, and secure at all times.

Operating range Y	2...10 V
Operating range Y note	4...20 mA w/ ZG-R01 (500 ?, 1/4 W resistor)
Input impedance	100 k? for 2...10 V (0.1 mA), 500 ? for 4...20 mA
Position feedback U	2...10 V
Bridging time (PF)	2 s
Pre-charging time	5...20 s
Angle of rotation	90°
Angle of rotation note	Adjustable with mechanical stop
Running Time (Motor)	75 s / 90°
Running time fail-safe	<60>
Noise level, motor	35 dB(A)
Noise level, fail-safe	35 dB(A)
Position indication	Pointer
Quality Standard	ISO 9001

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Datasheets and Brochures

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Datasheets and Brochures

It is designed for HVAC and ventilation systems where precise modulating damper control and automatic fail-safe positioning are required in the event of power loss.

SR indicates that the actuator supports modulating (proportional) control, allowing smooth, variable positioning rather than simple on/off operation.

An internal spring return mechanism automatically drives the damper to a predefined safe position when power is removed.

It operates on a 24V supply, making it ideal for low-voltage building automation and HVAC control systems.

Yes. It can be configured to move either open or closed on power loss, depending on the safety requirements of the application.

It is commonly installed on small to medium dampers in air handling units, VAV boxes, and ventilation systems in commercial, healthcare, and data centre environments.

Yes. Its compact design allows it to be fitted in tight areas such as ceiling voids and compact ductwork.

The spring return mechanism moves the damper to its safe position within seconds, ensuring rapid protection.

Yes. The modulating control interface allows seamless integration with modern BMS platforms for precise airflow management.

Maintenance is minimal, typically limited to routine functional checks and visual inspection. The internal spring mechanism is sealed for long-term reliability.

Yes. It is engineered for continuous duty and high cycle applications in demanding HVAC environments.

Selection depends on damper size, required torque, control method, and safety strategy. Matching these factors ensures reliable operation and compliance with system design requirements.

Please feel free to request information and advice using the form below or call us on 0151 547 1221

Belimo CQKB24-SR-LL Fail-Safe Actuator