The Siemens SSA81U is an advanced non-spring return (NSR) zone valve actuator designed to offer precise control in HVAC systems. Operating on a 24V power supply, this actuator utilizes a floating control signal to manage valve positioning efficiently. The Siemens SSA81U actuator is engineered for reliable control of zone valves in various HVAC applications. https://www.partshnc.com/24v-nc-fltng-nsr-zonevlvact