Core Features "STA21" Series & Functional Design: The "STA21" denotes Siemens’ entry-level light-duty linear actuator series, optimized for compact hydronic valve control in residential and small commercial settings. It is a 24V AC-powered linear actuator with a 10 mm stroke length and 500 N thrust rating (≈51 kgf)—ideal for small 2-way hydronic valves (e.g., residential radiator valves, small commercial fan coil unit valves) where 24V low-voltage power, balanced performance, and easy installation are prioritized. Flexible Control Modes & Optional Feedback: Equipped with dual control options to meet light-duty flow needs: On/off control (24V AC input): For simple full-open/full-close scenarios (e.g., residential heating zone on/off), ensuring reliable flow regulation with rapid actuation (≈3.3 seconds/full stroke). Modulating control (0–10V DC input, optional): For variable flow applications (e.g., small office FCU temperature adjustment), enabling valve opening adjustment with ±3% positioning accuracy—sufficient for stable room temperature control. It includes optional analog position feedback (0–10V DC) for valve status monitoring, compatible with residential smart thermostats or small commercial BMS. Compact & Lightweight Build: Engineered with a flame-retardant high-impact plastic housing (UL94 V-0) and a lightweight design of 0.55 kg (1.21 lbs), suitable for direct valve mounting (via mini ISO 5211 flange) or bracket installation in tight spaces (e.g., residential boiler closets, small HVAC enclosures). The housing features IP44 protection (dust-resistant, splash-proof), making it compatible with indoor residential and small commercial environments (e.g., apartments, small cafes). Safety & Reliability Features: Built with essential safeguards for long-term operation: Overthrust protection: Automatically stops the motor if thrust exceeds 500 N (e.g., valve stem jamming from mineral buildup), avoiding damage to the small valve or actuator. Thermal overload protection: Shuts down the motor in case of overheating (e.g., prolonged operation), extending component lifespan. 24V low-voltage safety: Designed for 24V AC (50/60 Hz) input with ±10% voltage tolerance, eliminating electrical hazards in occupied spaces. Simplified Installation & Integration: Designed for plug-and-play setup with no complex programming—works with Siemens residential controllers (e.g., RLU series) and third-party devices via standard 24V on/off or 0–10V signals. It includes a mini ISO 5211 flange (fits most small hydronic valves) and color-coded wiring terminals, reducing installation time to under 15 minutes for most applications. Typical Applications SIEMENS Actuator STA21 is engineered for light-duty linear control of small hydronic valves—ideal for scenarios needing 500 N thrust, 10 mm stroke, and 24V power in residential or small commercial systems. Key use cases include: Residential Radiator Heating: Controlling 2-way valves in residential radiator heating zones (e.g., bedrooms, living rooms). On/off control manages zone-specific heating, while compact size fits radiator enclosures—complying with EN 12831 (residential heating design) and ASHRAE 90.2 (residential energy efficiency). Small Commercial Fan Coil Units (FCUs): Regulating valves in small FCUs for office cubicles or hotel rooms. Optional modulating control adjusts water flow to match room temperature, and IP44 protection withstands FCU enclosure moisture—complying with EN 14511 (air handling units and FCUs). Residential Underfloor Heating Manifolds: Adjusting valves in residential underfloor heating manifolds (e.g., multi-room zones). 24V low-voltage compatibility aligns with home control systems, and lightweight design avoids manifold strain—complying with EN 1264-4 (underfloor heating systems). Light Commercial Beverage Systems: Controlling small valves in commercial beverage dispensers or countertop water coolers. Simple on/off control maintains fluid flow, and compact size fits appliance enclosures—complying with EN 15502 (food/beverage equipment standards).