The Siemens 3RN1011-2BM00 is a thermistor motor protection evaluation unit — it monitors PTC thermistor sensors embedded in motor windings and trips a relay when the winding temperature exceeds the sensor threshold. The unit carries two CO (changeover) auxiliary contacts for signaling or direct motor starter dropout. There are no NC or NO contacts beyond those — the two COs are the full contact set. Spring-loaded terminals handle the auxiliary and control wiring — no screwdriver needed for termination, which speeds up panel wiring and reduces loose-connection callbacks.
Housing is 22.5 mm wide, 103 mm tall, 91 mm deep. Fastening is screw and snap-on mounting. Rated IP20.
This part is marked as a phased-out product. The preferred successor is the 3RN2011-2BW30, which is a thermistor motor protection standard evaluation unit with manual/remote selection and a 2 W rating at 230 V AC. If you're filling a BOM for a new line, the successor is the cleaner path — same function, updated design. For existing panels using the 3RN1011-2BM00, the unit is available through independent channels. RoHS compliance date is May 28, 2009.