STC25

Electrothermal actuator for zone valves and terminal units, connectable to Siemens 2-way VGZ series, 3-way XGZ series, and 3-way 4-port XGZ+TXZ series valves. It consists of an expanding thermostatic element (PTC) which, upon receiving a 230 Vac command, causes a small piston to extend, pushing down the valve stem, overcoming the valve body's return spring. The actuator is designed with double thermal insulation, a plastic cover, and a manual control knob for operation without power.
The STC25 product comes standard with an auxiliary microswitch, whose function is usually to stop the circuit pump when the valve is closed.