The Siemens 3RN2012-1BW31 is a SIRIUS 3RN2 thermistor motor protection relay. It monitors motor winding temperature via PTC thermistors, tripping the output when the motor overheats. Rated supply 24... 240 V AC/DC, 50/60 Hz. Output rated 1 A at 24 V, 0.2 A at 125 V, 0.1 A at 250 V. IP20 enclosure, 22.5 mm wide, 100 mm high, 90 mm deep. Any mounting position.
Current production stage.
Rated supply 24... 240 V AC/DC covers 24 V and 240 V systems. Output rated 1 A at 24 V drops to 0.2 A at 125 V and 0.1 A at 250 V — enough to drive a contactor coil or PLC input, but not a direct motor starter. Bistable evaluation unit with open-circuit and short-circuit detection in the sensor circuit. No triggering on control supply failure. Auto-reset and external reset available. Error memory stores the last fault. Operates -25... +60 °C, stores -40... +85 °C. Pollution degree 3, so it handles conductive dust and condensation environments.
Any mounting position. Screw terminals accept 1x 20-12 AWG solid or stranded, 2x 20-14 AWG solid for daisy-chaining. Strip length 8 mm. Spring-cage not used here. LED display version gives visual status. Galvanic isolation between input and output, and between outputs.