What it is and what it does
The Siemens 3RU2116-1HB0-ZX95 is a SIRIUS thermal overload relay in Size S00, designed to protect motors against overload and phase failure by monitoring motor current and tripping the associated contactor when the thermal model exceeds the set point. 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 short, such as pumps, fans, and compressors. The relay mounts directly onto a contactor (contactor mounting), saving panel space and eliminating separate wiring between the relay and contactor coil.
Key ratings and what they mean for fit
Rated insulation voltage is 690 V, covering 400 V and 480 V systems with headroom. Motor power ratings are 3 kW at 400 V, 4 kW at 500 V, and 5.5 kW at 690 V — match these to your motor nameplate, not the contactor frame. Switching capacity varies by control voltage: 2 A at 24 V and 230 V, 3 A at 120 V, 1 A at 400 V, and 0.3 A at 60 V. The 120 V / 3 A rating is the highest — useful for pilot-duty control circuits in North American panels. Temperature compensation is active from -40 to +60 °C, so the trip curve stays accurate across the operating range without manual derating. MTTF of 2 280 years under high-demand rate reflects the thermal design — no moving parts in the sensing element, just a bimetal strip.
Mounting and wiring
Size S00 footprint: 45 mm wide, 76 mm high, 70 mm deep — fits standard 45 mm DIN-rail spacing when mounted on the contactor. Main circuit terminals accept 2 × (0.5 to 1.5 mm²) solid or stranded, or 2 × (0.75 to 2.5 mm²) — screw-type with Pozidriv PZ 2 tip, shaft diameter 5 to 6 mm. Auxiliary switch is integrated into the relay housing — no separate add-on block needed for the trip-indication contact. Mounting position is any orientation, simplifying panel layout in tight enclosures.