The Siemens 5SU9356-7KK50 is a SENTRON RCBO — an RCD-operated circuit breaker combining overcurrent and residual-current protection in a single 36 mm-wide module. Rated 50 A with a Type A fault-current sensitivity and tripping characteristic C, it handles the mixed loads common in commercial and light-industrial panels: motor starters, lighting circuits, and socket outlets with electronic equipment that generates pulsed DC fault currents. The 6 kA breaking capacity per EN 60898 covers most sub-distribution applications; the 10 kA rating per IEC 60947-2 gives headroom where the prospective fault current is higher.
What the ratings mean for fit
Type A detection means this RCBO trips on sinusoidal AC residual currents and also on pulsating DC fault currents up to 6 mA — the kind a half-wave rectifier or a switched-mode power supply can produce. That makes it the right choice for circuits feeding computers, LED drivers, or variable-speed drives where a plain AC-sensitive RCD might not see the fault. The C-curve (5–10× In magnetic trip) avoids nuisance tripping on motor inrush or capacitive loads while still clearing a hard short fast enough to protect the cable. Rated current derates with ambient temperature: 50 A at 30 °C, 47 A at 40 °C, 45.5 A at 45 °C, 43.5 A at 50 °C, and 40.5 A at 55 °C. If the panel runs hot — say a crowded enclosure near a furnace line — size the upstream breaker for the derated figure, not the 50 A label. The 1.5 W maximum power dissipation per unit matters when stacking multiple RCBOs on a DIN rail; total heat load adds up fast in a sealed enclosure.
Mounting and wiring
Snaps onto standard 35 mm DIN rail, occupies 2 width units (36 mm). Installation depth is 70 mm; the overall depth is 77 mm including the front projection. Mounting position is any — no restriction on upright or sideways orientation. The supply cord can enter from either top or bottom, which simplifies bus-bar routing in a crowded panel. Terminal capacity accepts solid or stranded conductors from 0.75 mm² up to 35 mm², covering most sub-feed and branch-circuit wire sizes. IP20 protection applies once the distribution board is installed with conductors connected — not rated for wet or dusty environments without an enclosure.