Siemens Actuator SQN70.254B20

The Siemens SQN70.254B20 is an actuator designed for automatic control of air dampers in burner systems, suitable for medium and low power burners. It operates on a 220 V supply at 50–60 Hz, delivers a torque of 1.5 Nm, and has a runtime of 4 seconds for a 90° rotation. The actuator supports three-point, 0-10 V, or on/off control signals, includes built-in stall protection, and features adjustable cams for switching points. It has a protection class of IP40 and provides position indication with an opening angle scale of 0…130°. This model supersedes the SQN70.254A20 and is fully compatible in mounting and electrical parameters.

When selecting a replacement actuator of this type, ensure the supply voltage, frequency, torque, runtime, rotation angle, and control signal type match the original. Verify the mounting pattern, shaft dimensions, and wiring configuration. The actuator may have a manual shaft disconnect with automatic re-engagement, and adjustable cams for setting switching points. Check the mechanical linkage and condition of the connected damper or valve before installation.

Typical failures for actuators of this class include stripped gear trains, failed end switches, or a seized valve stem after prolonged inactivity. Symptoms may include the damper not moving or moving erratically, unusual noises, or the burner not operating correctly. Check the actuator's operation, wiring, and mechanical linkage for issues.