Siemens Actuator SQN30.111A3500

This Siemens actuator is a servo motor which positions air dampers or mixing valves in burner and boiler systems. It rotates counterclockwise, delivers a torque of 1.5 Nm, and has a running time of 4.5 seconds per 90 degrees. Its housing is 110 mm long and it is equipped with two auxiliary switches. The unit corresponds to diagram number 1 in the technical documentation. It converts a control signal from the burner control or modulating controller into mechanical rotation to regulate air or water flow.

Replacements of this kind are chosen by matching the required torque, running time, control signal type, and shaft dimensions. Verify whether a clockwise or counterclockwise rotation direction is needed and whether auxiliary switches are required for end-position feedback or interlocks. Before ordering, compare the mounting dimensions, coupling, and angle of rotation with the existing damper or valve, and confirm that the electrical connections are compatible with the burner control wiring.

Typical failures include stripped gears that stop the damper or valve mid-travel or cause erratic movement. Worn or stuck auxiliary switches may give false feedback or fail to indicate the end position, so the controller continues to drive the motor. A valve stem that has seized during a long shutdown can overload the actuator and burn out the motor or break the drive train. Before installing a new unit, make sure the valve stem turns freely and inspect the gear mechanism and auxiliary switches for wear or sticking.