“Stella” – the intelligent autonomous electrothermal valve actuator 230 VAC NC for automatic adaptive hydronic balancing of the heating circuits of a heating circuit manifold in panel heating and cooling systems. Sensors on the flow and return pipes measure temperature differences and an algorithm continuously calculates the required temperature spread and the corresponding valve position. Closed when de-energized and with hinged lever for relieved unscrewing or for de-energized manual opening of the thermostatic valve. With integrated flow temperature limiter. Stella can be used in combination with all standard temperature controllers and terminal strips. When using devices with a triac switching element, a dielectric strength (V DRM) of the triac of at least 800V is required.