De Dietrich 200005398 Servomotor STA 30 B2 37 / 6 3N32L

This servomotor, branded De Dietrich, is a rotary actuator of the type used to position air dampers and mixing valves in heating systems. Such actuators convert a control signal into rotational movement to regulate airflow or water flow. In a boiler or burner system, a servomotor may be coupled to an air damper to modulate combustion air during the firing sequence, or to a three-way or four-way valve to blend or divert flow between heating circuits and domestic hot water. When selecting a replacement servomotor of this class, the key parameters are torque, running time, control signal type (three-point, 0-10 V, or on/off), shaft or coupling pattern, angle of rotation, and the presence of integral auxiliary switches. Parts of this type are typically separate from the valve body, meaning the motor is a spare part for the valve assembly. Common failures in such servomotors include stripped gear trains, failed end switches, or a seized valve stem after prolonged standstill. Ensuring the new actuator matches the original’s mechanical interface and control logic is essential for correct operation. The catalogue reference for this article is 336.712.001, with manufacturer codes 200005398 and 336.712.001. No specific technical ratings are provided here; the part should be cross-referenced against the existing installation’s requirements.