The Siemens SIRIUS 3RV2021-1KA10-0DA0 is a circuit breaker designed for system protection — meaning it sits upstream of a motor starter or contactor to guard against short circuits and overloads in the distribution path, not as a standalone motor-protective device.
Breaking capacity — the number that decides selectivity
At 400 V AC, this breaker interrupts 100 kA. Same at 240 V AC.
Motor protection and trip class
Rated motor power at 230 V is 3 kW. Trip class is CLASS 10 — that's the standard for standard-duty motor starts (pumps, fans, compressors) where the start time stays under 10 seconds. If you're driving a high-inertia load like a centrifuge or a large flywheel, CLASS 10 may trip on start; you'd step to CLASS 20 or 30. The breaker accepts 2x (1 to 2.5 mm²) or 2x (2.5 to 10 mm²) solid or stranded wire at the main contacts, M4 screw terminals.
Mounting position is any. Clearances: 50 mm upwards, 50 mm downwards, 30 mm at the side, 0 mm forwards and backwards — so it can be stacked tight front-to-back in a shallow enclosure. Dimensions: 45 mm wide, 97 mm high, 97 mm deep. The S0 frame is the same width as the S00 but taller, so if you're swapping from an S00 breaker, check the height clearance in your enclosure.