Title: Siemens STA73-eng.pdf
Technical and mechanical designActuator operationThe electrothermal actuators STA.. and STP.. are noise-free and maintenance- free. When the control signal is applied to the actuator, the temperature of the heating element rises, which causes the solid expansion medium to expand. It transfers its stroke directly to the installed valve. The valve starts to open after preheating for approx. 1 min if the heating element is switched on in a cold state (room temperature), and achieves the maximum stroke after another approx. 2.5 min (230 V) or 3 min (24 V). At power-off, the expansion element cools down and the valve will be closed by the spring. This has the following effect for the actuator types below:STA73.., STA23.. (NC) 2-position, PDMThe actuator stem retracts and the radiator valve is opened by the own spring. The actuator stem extends when de-energized and the radiator valve is closed.STP73.., STP23.. (NO) 2-position, PDM