The Siemens 3RN2023-1DW30 is a SIRIUS 3RN2 thermistor motor protection relay designed to monitor motor winding temperature via PTC thermistors. It features two independent sensor circuits for warning and disconnection, with open-circuit and short-circuit detection in both circuits, plus safe disconnection and non-volatile error memory. The relay operates on a rated supply voltage of 24 to 240 V AC/DC and mounts via screw or snap-on onto 35 mm DIN rail.
Key Ratings and What They Mean
MTBF of 97 a and MTTFd of 303 a indicate a long service life under typical industrial conditions — the relay is built for continuous operation in motor control centers where downtime is costly. The 24 to 240 V AC/DC supply range covers most global control voltages, so no separate power supply module is needed for 24 V or 120 V panels. The relay includes ATEX approval and two sensor circuits, meaning it can monitor two separate PTC chains (e.g., one for alarm, one for trip) in hazardous-area motor applications. Open-circuit and short-circuit detection in both circuits ensures fault conditions are caught even if the sensor wiring is damaged.
Where It's Used
This class of thermistor motor protection relay is used in motor control panels for pumps, fans, conveyors, and compressors where winding overtemperature must be detected to prevent motor burnout. The ATEX variant suits Zone 1/21 motor circuits in oil & gas, chemical, or grain-handling environments.