The Siemens 5SU9406-1KK32 is a SENTRON RCBO — a combined RCD and MCB in one 18 mm-wide package, rated 32 A with a C tripping characteristic and 6 kA breaking capacity per EN 60898. It protects a single-phase final subcircuit (1P+N) against overload, short-circuit, and earth leakage in one unit, saving a DIN rail position compared to separate devices.
Ratings and what they mean on site
The 32 A rating at 30 °C is the headline number, but the thermal derating curve matters more when the panel runs warm: at 40 °C it's 30.08 A, at 45 °C it's 29.12 A, and at 50 °C it drops to 27.84 A (–). If your panel ambient sits at 45 °C, size the downstream load to 29 A, not 32. The C-curve means the magnetic trip fires at 5–10× In — standard for motor and lighting circuits with moderate inrush. The 6 kA breaking capacity is the fault current it can safely interrupt; fine for most commercial and light industrial sub-distribution boards, but check your prospective short-circuit current at the point of installation. It accepts solid or stranded conductors from 0.75 to 35 mm², which covers everything from 1.5 mm² lighting tails up to 10 mm² feeder tails. The 18 mm width means it occupies one modular unit on the DIN rail — no space penalty for the combined RCD/MCB function.
Where it fits in the panel
Mounts on a standard 35 mm DIN rail; installation depth is 70 mm, total depth 77 mm. The supply can enter from top or bottom. Rated IP20 with connected conductors and the distribution board installed — it's an enclosed-panel part, not for standalone outdoor use. Halogen-free and silicon-free for environments where off-gassing matters.