SIRIUS thermal overload relay, Size S0, Class 10
The Siemens 3RU2126-1JJ0 is a SIRIUS thermal overload relay, Size S0, with Trip Class 10 — meaning it trips within 10 seconds at 7.2× the set current, matching the typical startup profile of standard AC induction motors. Rated for 690 V and delivering 4 kW at 400 V, 5.5 kW at 500 V, and 7.5 kW at 690 V, it is sized for motor protection in 50/60 Hz circuits. The thermal bimetallic release compensates from -40 to +60 °C, so the trip curve stays accurate across the panel environment.
Mounting and integration
Mounts directly to the contactor via the fastening method specified; no separate DIN-rail base required. Accepts any mounting position, and the auxiliary switch is integrated — no add-on block needed for the trip signal. Main circuit connections use ring cable lugs (M4 screw), so the wiring stays secure under vibration. Dimensions: 85 mm wide, 45 mm deep, 85 mm tall — fits the standard S0 footprint.