The Siemens 3RU2116-0BC0 is a SIRIUS thermal overload relay in size S00, designed to protect motors against overload and phase failure. It is Trip Class 10, meaning it will trip within 10 seconds at a 7.2× current overload — the standard for standard-duty induction motors on pumps, fans, and conveyors where starting time is under 10 seconds. The integrated auxiliary switch provides status feedback: normally-open contact rated 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V — enough to signal a PLC input or drop out a contactor coil directly. The relay mounts directly onto the contactor (fastening method: contactor mounting), saving panel space and wiring. Termination is via spring-loaded terminals accepting 2x (0.5... 2.5 mm²) solid or stranded wire — no screw torque to verify, which speeds panel assembly. The relay can be mounted in any position, with temperature compensation active from -40 to +60 °C, so it works in unconditioned enclosures near ovens or outdoor cabinets.
Key Ratings and What They Mean
Rated insulation voltage 690 V covers 400 V and 480 V systems with margin — suitable for IEC and most North American 600 V class installations. The auxiliary contact's 400 V rating at 1 A is the AC-15 inductive load figure; at 120 V it handles 3 A, enough for a 120 V contactor coil. The note 'for message Tripped' on the relay indicates that the auxiliary contact position changes only when the overload relay has tripped — it does not change on manual test or reset. This is important for the control logic designer: the PLC sees a trip signal, not a test signal. Dimensions: 87 mm high, 45 mm wide, 70 mm deep — the S00 footprint matches the Siemens 3RT2 contactor series. The 70 mm depth fits standard 80 mm deep enclosures with clearance for wiring.