The Siemens SIRIUS 3RN2000-2AA30 is a compact thermistor motor protection relay from the 3RN2 family, designed to monitor motor winding temperature via PTC thermistor sensors (bimetallic switch type). It's a dedicated evaluation unit — not a general-purpose overload relay — so it sits upstream of the contactor in the motor branch, tripping the coil when the thermistor circuit resistance rises above the threshold. Rated supply is 24 V AC/DC (50/60 Hz), and the output relay switches up to 1 A at 24 V or 0.2 A at 125 V — enough to drive a contactor coil or PLC input. The unit auto-resets when the winding cools, with no error memory, so it's suited for applications where a manual reset isn't required. Housing is 17.5 mm wide — one standard DIN-rail module — with push-in spring-cage terminals accepting 20–12 AWG solid or stranded wire.
RoHS compliance date is May 28, 2009, so it meets the EU directive for current builds. No UL or CSA listing appears in the spec record, but the IP20 and pollution degree 3 ratings align with typical industrial panel requirements.
Mounting & Wiring Notes
The 17.5 mm width means it takes up one slot, leaving room for a contactor and overload block in the same row. Spring-cage terminals: strip 8 mm, push in, done. Solid or stranded 20–12 AWG fits without ferrules. The design requires terminal A1 to be jumpered with the root of the changeover contact for proper thermistor circuit sensing. An LED on the front gives visual trip indication — useful during commissioning or troubleshooting. Clearance: zero mm required upwards, downwards, forwards, backwards, and at the sides — so it can be packed tight against other devices without derating for airflow.