SIRIUS Size S2 thermal overload relay, Class 10A
The Siemens 3RU2136-4RD0 is a SIRIUS Size S2 thermal overload relay, Trip Class 10A, rated 690 V. It mounts directly to a contactor and protects motor circuits against overload and phase unbalance. The Class 10A trip curve means it will trip within 10 seconds at 7.2× the current setting — fast enough for standard induction motor starts without nuisance tripping on normal acceleration. Rated for motor loads up to 37 kW at 400 V and 75 kW at 690 V. The thermal bimetal release compensates for ambient temperature changes between -40 and +60 °C, so the protection stays accurate whether the panel is in a cold warehouse or a warm production floor.
Mounting and wiring
Fastens directly to the contactor — no separate DIN-rail footprint needed. The Size S2 frame mates with the corresponding SIRIUS contactor range. Main circuit connections are screw-type terminals; the auxiliary switch is integrated. Wire capacity is 2 × (0.5 to 2.5 mm²) solid or stranded per clamp. Mounting position is any orientation. The screw terminals accept a Pozidriv PZ 2 bit with a shaft diameter of 5 to 6 mm.