The Siemens 3RN1012-2BM00 is a thermistor motor protection evaluation unit from the SIRIUS 3RN1 series, designed to monitor motor winding temperature via PTC thermistors and trip the contactor when the motor overheats. It operates on a 230 V AC supply at both 50 and 60 Hz, and includes a reclosing lockout function that prevents automatic restart after a fault — important for applications where a manual reset is required for safety.
The 3RN1012-2BM00 is a phased-out product. The preferred successor is the 3RN2012-2BW30, which offers the same thermistor motor protection function with manual/auto/remote selection and 2 W power consumption. No spare, no sleep: if you're holding a critical spare for a legacy motor starter, this is the one to keep in the cabinet.
This evaluation unit is part of the motor feeder protection chain in industrial control panels — typically paired with a contactor and overload relay to protect motors against overtemperature caused by overload, blocked rotor, or cooling failure. The reclosing lockout ensures that after a thermal trip, the motor cannot restart until the fault is acknowledged, which is standard for conveyors, pumps, and compressors in process lines.