What it is and what it does
The Siemens 3RU2116-0BC1 is a SIRIUS thermal overload relay, size S00, designed to protect motors against overload and phase failure by monitoring the motor current and tripping the contactor when the thermal model exceeds the set threshold. Its Trip Class 10 means it will trip within 10 seconds at 7.2× the set current — standard for general-purpose motor starting where the acceleration time is under 10 seconds. Rated insulation voltage is 690 V, covering 400 V and 480 V systems with margin.
Key ratings and what they mean for fit
The auxiliary contact is rated at 2 A at 24 V, 3 A at 120 V, and 2 A at 230 V — these are the switching capacities for the N/C and N/O signaling contacts that feed the PLC input or the contactor coil circuit. At 400 V the relay is rated for 0.06 kW motor load; at 690 V it is rated for 0.09 kW — these are the maximum three-phase motor ratings at the respective line voltages, so size the overload relay to the motor FLA, not the other way. The relay compensates for ambient temperature changes between -40 and +60 °C, so it tracks the motor's thermal state rather than the panel's internal temperature. Operating temperature range is -40 to +70 °C, storage and transport range is -55 to +80 °C.
Mounting and wiring
Fastening method is stand-alone installation — it mounts directly to the contactor or on a DIN rail via the contactor's base, not on a separate rail adapter. Mounting position is any, so it can be installed horizontally, vertically, or flat without derating. Main current circuit uses spring-loaded terminals accepting 2 × (0.5 to 2.5 mm²) solid or stranded wire — no screw torque to verify, just strip and push. Dimensions are 45 mm wide, 79 mm deep, 102 mm high — fits the S00 contactor footprint.
Lifecycle and sourcing
The auxiliary switch is integrated into the relay body, not a separate add-on module. Substance prohibitance date is 10/01/2009 — the relay complies with RoHS and REACH substance restrictions as of that date. MTTF with high demand rate is 2,280 years — a reliability figure for safety-related applications where the relay is exercised frequently.
What the 'Tripped' note means
The relay carries a note 'for message Tripped' — this refers to the auxiliary contact configuration that signals a trip condition to the control system, typically a N/C contact that opens when the relay trips.