Siemens Actuator SQN71.424B20

The Siemens SQN71.424B20 actuator is a device designed to control the air damper in burners, regulating air supply for fuel-air mixture preparation and combustion chamber purging. It operates on a supply voltage of 220–240 V and a frequency range of 50–60 Hz, with a torque of 2.5 Nm and a runtime of 12 seconds for a 90° opening. The actuator has a maximum rotation angle of 160°, a protection class of IP40, and a net weight of 0.5 kg. Its dimensions are 11.7x6.6x9 cm, and it consumes 6 W of power. The drive motor is a reversing synchronous motor, and the housing is made of impact-resistant, heat-resistant plastic, with a steel drive shaft. It includes built-in position indication and is suitable for small and medium power burners using gas or liquid fuel. This model is the replacement for SQN71.424A20 and has the manufacturer part number 884.712.199.

When selecting an actuator of this type, verify that the supply voltage, frequency, torque, runtime, and rotation angle match the burner's requirements. Check the shaft coupling and mounting dimensions to ensure compatibility with the existing damper linkage. The control signal (e.g., three-point or on/off) must be compatible with the burner control unit. Confirm the presence and configuration of auxiliary switches if needed for end-position feedback.

Common failures include stripped gear trains, failed end switches, or seized shafts after prolonged inactivity. Symptoms may include the damper not moving or moving erratically, burner ignition issues, or incomplete purging. Check for mechanical obstructions, electrical continuity in the motor windings, and proper operation of limit switches.