Honeywell Servo motors LKS120-21 (B5-5S1) 78-LKS120-21

The Honeywell LKS120-21 (B5-5S1) is a servo motor designed for use in single-stage and two-stage burners, with or without a fully closing flap. It operates on a 230 V supply, consumes 9 W, and delivers a torque of 75 Nm with a runtime of 5 seconds for a 90° rotation. The actuator features a synchronous motor with gearboxes housed in synthetic materials, offering IP31 protection. It connects via a 5-pole terminal block and is installed using through holes for M5*50 screws. The unit weighs 500 g and requires no maintenance.

When selecting a replacement servo motor for a burner, ensure the supply voltage, torque, runtime, and rotation angle match the original specifications. The mounting hole pattern and shaft dimensions must be compatible with the existing linkage. Check the electrical connection type and the number of terminals to match the control system. For this type of actuator, installation typically involves securing it with M5 screws through the provided holes and wiring the terminal block according to the wiring diagram.

Common failures in servo motors of this kind include gear wear, motor burnout, or electrical connection issues. Symptoms may include the actuator not moving, moving slowly, or making unusual noises. The burner may fail to modulate correctly or get stuck in one position. Check for proper voltage supply, inspect the wiring and connections, and listen for abnormal sounds during operation.