The Siemens SENTRON 5SU9356-1CS20 is a 2-pole (1P+N) RCD-operated circuit breaker — a combined residual-current device and miniature circuit breaker in one 36 mm wide (2 MW) package. Rated 20 A at 30 °C with a C tripping characteristic, it protects final circuits against overload and short-circuit while also detecting AC earth faults. The C-curve means it trips between 5 and 10 times rated current, suited for loads with moderate inrush like small motors, pumps, or lighting banks.
Ratings and derating
Current rating is temperature-dependent: 20 A at 30 °C ambient, derated to 18.8 A at 40 °C, 18.2 A at 45 °C, 17.4 A at 50 °C, and 16.2 A at 55 °C. The operating ambient range is -25 to +45 °C. Breaking capacity is 6 kA per EN 60898 and 10 kA per IEC 60947-2 — the higher figure applies when the device is used as a circuit breaker per the product standard, giving headroom for installation close to the service entrance. Rated frequency is 50 Hz. Overvoltage category III means it is designed for fixed installation downstream of the main distribution board.
Installation and wiring
Mounts on DIN rail in any position. Accepts solid or stranded conductors from 0.75 to 35 mm². Installation depth is 70 mm; overall depth 77 mm. Supply can enter from top or bottom. Touch protection is built in. IP20 rating applies when the distribution board is installed and conductors are connected. Halogen-free and silicon-free construction — relevant for environments sensitive to corrosive outgassing, such as data centers or clean rooms.