RCD-operated circuit breaker — 20 A, Type A, C-curve
The Siemens SENTRON 5SU9356-7KN20 is an RCBO — a combined RCD and MCB in one 2-module (36 mm wide) package. It carries a 20 A rated current at 30 °C with a C tripping characteristic, so it handles moderate inrush from motor starters or lighting banks without nuisance trips. The Type A RCD detects pulsating DC fault currents as well as sinusoidal AC, which covers variable-speed drives and electronic loads. Breaking capacity is 6 kA per EN 60898 for domestic-style distribution boards and 10 kA per IEC 60947-2 for industrial panels — the higher figure gives you coordination headroom on the industrial side. Rated current derates with ambient temperature: 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. If the panel runs hot, size the load accordingly. The RCBO is halogen-free and silicon-free, which matters for clean-room or food-grade installations where outgassing can contaminate product.
Mounting and wiring
Mounts on DIN rail, any position. Installation depth is 70 mm, overall depth 77 mm — verify enclosure depth if retrofitting into a shallow panel. Accepts solid or stranded conductors from 0.75 mm² up to 35 mm², which covers most subfeed and branch-circuit sizes. Supply can enter from top or bottom; the RCBO is polarity-sensitive on the 1P+N configuration (switched phase, solid neutral). Touch protection is built in, and IP20 is maintained once the distribution board is installed with conductors connected.