The Siemens 3RN2010-1CA30 is a SIRIUS 3RN2 thermistor motor protection relay — a compact evaluation unit designed for bimetallic switch sensors. It runs on a 24 V AC/DC supply and its output switches 1 A at 24 V, which is enough to drive a downstream contactor coil or PLC input directly. Auto-reset is enabled out of the box, so it clears the fault latch once the motor cools below the PTC threshold; no external reset button needed.
Mounting and fit
The 17.5 mm width (one module) means it takes up a single slot in a terminal-block-style rail assembly. Clearance around the housing: 0 mm upwards, forwards, backwards, downwards, and at the side — it can sit flush against other devices or the panel wall with no extra air gap.
Output and reset behaviour
The output is rated 1 A at 24 V, 0.2 A at 125 V, and 0.1 A at 250 V — so keep the load within those limits, especially if you're switching an AC contactor coil at line voltage. Galvanic isolation between the output and the input is confirmed, and also between the two output channels if you're using the dual-channel variant. The LED on the front gives a visual trip indication, which helps during commissioning or fault-finding without needing a meter.