RCD-MCB with Type A sensitivity and dual breaking capacity
The Siemens 5SU9356-7KK63 is a 2-pole (1P+N) RCD-operated circuit breaker from the SENTRON 5SU9 series, combining overcurrent protection with residual-current detection in a single 36 mm wide DIN-rail module. It carries a 63 A rated current at AC with a C tripping characteristic, meaning it handles moderate inrush from motor or lighting loads without nuisance trips. The Type A fault-current design detects both sinusoidal AC and pulsating DC residual currents — the standard choice for circuits with single-phase rectifiers, switched-mode power supplies, or variable-speed drives downstream. Breaking capacity is rated at 6 kA per EN 60898 (the domestic-standard curve) and 10 kA per IEC 60947-2 (the industrial-standard curve). The higher 10 kA figure gives the headroom needed for commercial or light-industrial distribution boards where fault currents exceed 6 kA. The 10 kA SCCR at 400 V means it safely interrupts faults up to that level without cascading upstream.
Current derating and thermal limits
The 63 A rating holds at 30 °C ambient. At 40 °C it derates to 59.22 A, at 45 °C to 57.33 A, at 50 °C to 54.81 A, and at 55 °C to 51.03 A. If the distribution board runs warm — common in crowded enclosures — size the upstream protection for the derated value, not the 30 °C figure. Operating ambient range is -25 to +45 °C; storage range extends to -40 to +75 °C.
Panel integration and wiring
The module occupies 2 width units (36 mm) on a DIN rail, with a depth of 77 mm and an installation depth of 70 mm. Mounting position is any orientation. Terminals accept solid or stranded conductors from 0.75 to 35 mm² — enough for the 63 A feed-through. Supply can enter from either top or bottom, which simplifies busbar routing in multi-row panels. IP20 rated with conductors connected and the distribution board installed.