The Siemens 3RU2116-1BJ0 is a SIRIUS thermal overload relay in Size S00, designed for direct contactor mounting to protect motors against overload and phase failure. Its Trip Class 10 characteristic means it will trip within 10 seconds at 7.2× the current setting — fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starts.
Ratings and what they mean for fit
The relay is rated for a maximum operating voltage of 690 V and carries switching current ratings that vary by voltage: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, and 0.75 A at 690 V. These are the continuous thermal current ratings through the normally-closed trip contact — the contact that breaks the contactor coil circuit on overload. For a 400 V motor circuit, the 1 A rating at 400 V means the relay's auxiliary contact can safely interrupt the coil current of most contactors up to that size; the motor's full-load current is handled by the overload's own bimetal heater, not this contact. Power dissipation per pole is 1.9 W, so in a panel with multiple relays side-by-side, the cumulative heat rise stays manageable — no forced cooling required for typical layouts. The relay compensates for ambient temperature changes between -40 °C and +60 °C, keeping the trip curve accurate across the panel's operating range.
Mounting and integration
Fastening is by direct contactor mounting — the relay clips onto the contactor's body, sharing the same DIN-rail footprint. No separate panel space or wiring between contactor and relay; the power connections pass through the relay's ring cable lug terminals (M3 screws for the main circuit). Mounting position is any, so vertical or horizontal orientation in the enclosure is fine. Dimensions are 45 mm wide, 76 mm high, 70 mm deep — a compact footprint that fits standard 45 mm wide contactor slots in the SIRIUS S00 frame. The auxiliary switch is integrated into the relay body, so no separate add-on block is needed for the trip indication.