Siemens Actuator Servomotor SQN72 / SQN73 Series

Siemens Actuator Servomotor SQN72 / SQN73 Series for Burner Damper Control

The Siemens Actuator Servomotor SQN72 / SQN73 Series is an electromotoric actuator designed for driving and positioning air dampers, gas dampers, and associated control valves in small- to medium-capacity oil and gas burner systems. It helps regulate combustion air and fuel supply according to burner load requirements, supporting appropriate combustion control.

The actuator incorporates a synchronous motor, reduction gear mechanism, and camshaft assembly for adjusting the operating positions of the end switches and auxiliary switches. It provides an operating torque of 1.5–2.5 Nm and a holding torque of 0.7–1.3 Nm, with a 90° running time of approximately 4–30 seconds depending on the model. The SQN72 rotates counterclockwise, while the SQN73 rotates clockwise.

Key Features

• Designed to position air dampers, gas dampers, and associated burner control valves

• Equipped with a synchronous motor and maintenance-free reduction gear mechanism

• Operating torque (Loading Torque): 1.5–2.5 Nm, depending on the model

• Holding torque: 0.7–1.3 Nm

• Running time for 90° rotation: approximately 4–30 seconds at 50 Hz

• Power supply: AC 230 V, 50–60 Hz

• SQN72: counterclockwise rotation; SQN73: clockwise rotation

• Adjustable end switches and auxiliary switches using cam disks

• Built-in internal position indication

• Impact-resistant and heat-resistant plastic housing

• IP54 protection rating when installed according to the manufacturer's specifications

• Supports two-stage and modulating burner control systems, depending on the circuit configuration and associated equipment

Technical Specifications

The Siemens SQN72 / SQN73 Series is an electromotoric actuator powered by a synchronous motor. It operates on an AC 230 V power supply with a voltage tolerance of -15% to +10% and a frequency of 50–60 Hz ±6%. Maximum internal power consumption is 6 VA.

Depending on the specific model, the actuator provides an operating torque (Loading Torque) of 1.5–2.5 Nm and a holding torque of 0.7–1.3 Nm. The running time for a 90° rotation is approximately 4–30 seconds at 50 Hz. The maximum usable positioning angle is 160°, with an angle scale ranging from 0–130°.

Regarding rotation direction, the Siemens SQN72 operates counterclockwise, while the Siemens SQN73 operates clockwise when viewed from the shaft end under the conditions specified by the manufacturer.

The actuator provides an IP54 degree of protection according to EN 60529 when installed correctly. Its operating temperature range is -20 to +60°C, with permissible relative humidity below 95% under non-condensing conditions. The maximum installation altitude is 2,000 meters above sea level.

The actuator weighs approximately 500 g and has a designed service life of 250,000 start cycles under the specified manufacturer's operating conditions. This designed lifetime is not equivalent to the product warranty period.

Operating Principle and Applications

The Siemens SQN72 / SQN73 Series adjusts the position of air and gas dampers according to control signals from the burner control system. Its internal camshaft mechanism determines the switching points of the end switches and auxiliary switches, enabling controlled damper positioning.

The series is suitable for industrial oil and gas burner applications, including boiler burner combustion control, air and gas damper positioning, and compatible two-stage or modulating burner systems.

Depending on the specific wiring configuration, these actuators can operate with Siemens burner controllers such as LME, LMO, LOA, LFL, LAL, LGK16, and LOK16. They can also be integrated into relevant load-control applications using RWF50 / RWF55 controllers. Model compatibility and electrical circuit requirements must be verified before installation.

Important Selection Considerations

When selecting a Siemens Actuator Servomotor SQN72 / SQN73, verify the exact model number, rotation direction, operating torque, 90° running time, drive shaft dimensions, electrical connections, and compatibility with the existing burner controller.

For replacement applications, these specifications should be checked against the original actuator to ensure proper installation, compatible operation, and safe burner performance.

Siemens SQN72 / SQN73 Series actuator for air and gas damper control in oil and gas burners. Operating torque 1.5–2.5 Nm, AC 230 V power supply, and IP54 protection.