What this RCBO is and what it does
The Siemens 5SU9356-1KN63 is a 2-pole (1P+N) RCD-operated circuit breaker from the SENTRON 5SU9 series, combining overcurrent protection and residual current detection in a single 36 mm wide unit. It is rated 63 A at 30 °C with a C tripping characteristic, meaning it handles moderate inrush loads like motor starters and lighting banks without nuisance tripping, while still clearing short-circuit faults quickly. The integrated residual current element detects AC fault currents at 30 mA, providing personal protection against direct contact.
Breaking capacity and selectivity
This RCBO carries a 6 kA rated short-circuit capacity per EN 60898 and a 10 kA rating per IEC 60947-2. The higher IEC figure applies when the device is installed per the manufacturer's instructions — typically in an industrial distribution board with an upstream backup fuse or MCCB. For a panel builder, the 10 kA SCCR at 230/240 V AC means this unit can be placed downstream of a transformer or main breaker rated up to that fault level without cascading upstream. The energy limiting class of 3 keeps let-through energy low enough to protect downstream wiring.
Thermal derating and mounting
The 63 A rating holds at 30 °C ambient. Above that, derate linearly: 59.22 A at 40 °C, 57.33 A at 45 °C, 54.81 A at 50 °C, and 51.03 A at 55 °C. In a crowded enclosure with multiple RCBOs ganged, the effective current per device drops — plan your load per the 40 °C or 45 °C column if the panel ambient runs warm. The unit snaps onto a DIN rail (35 mm per EN 60715) and can be mounted in any position. The 77 mm depth plus 70 mm installation depth fits standard 100 mm deep enclosures with room for wiring. Supply can enter from top or bottom, which simplifies busbar routing.