What this RCBO does on the rail
The Siemens 5SU9356-7KN63 is a 2-pole RCD-operated circuit breaker (RCBO) from the SENTRON family, combining overcurrent protection and residual current detection in a single 2-module-width (36 mm) package. It's rated 63 A at 30 °C with a C tripping characteristic for moderate inrush loads like motor starters and small transformer banks, and a 30 mA Type A residual current trip for sinusoidal AC and pulsating DC fault currents. The interrupting capacity is 6 kA per EN 60898, which covers most final-subcircuit fault levels in commercial and light industrial distribution boards. Mounting position is unrestricted, and the supply can enter from top or bottom — useful when retrofitting into an existing panel where the busbar orientation is already set.
Derating and ambient — the real-world current
The 63 A rating holds at 30 °C ambient. At 40 °C it's 59.22 A, at 45 °C it's 57.33 A, at 50 °C it's 54.81 A, and at 55 °C it's 51.03 A. If the distribution board runs warm — say, a packed enclosure near a drive cabinet — use the 40 °C figure for your continuous load calculation. The RCBO is halogen-free and silicon-free, which matters in clean-room or semiconductor-adjacent installations where outgassing can contaminate optics or wafers.