What this RCBO is and what it does
The Siemens 5SU1356-1KK10 is a SENTRON-series RCBO — a combined residual-current device and miniature circuit breaker in a single 2-module-width (36 mm) package. It protects a 1P+N circuit (one protected pole, switched neutral) against overloads, short-circuits, and earth faults. The C tripping characteristic means it handles moderate inrush currents common with motor starters, contactor coils, and small transformers without nuisance trips. Rated 10 A at 30 °C ambient, it derates to 8 A at 70 °C — a real concern if this RCBO sits in a crowded, warm enclosure. The full derating curve is published, so a panel builder can size it accurately for the actual operating temperature rather than guessing. Breaking capacity is 6 kA per EN 60898 and 15 kA per IEC 60947-2. The higher IEC figure matters when the RCBO is used in industrial panels with higher available fault current — it tells you the device can interrupt a 15 kA fault without welding its contacts. Overvoltage category III and pollution degree 2 suit fixed-installation distribution boards.
Where it fits — panel and environment
Snaps onto a DIN rail (35 mm) and occupies 2 modular width units (36 mm). Depth is 77 mm, installation depth 70 mm — the extra 7 mm is the front toggle and test button. Mounting position is any, so it works in vertical or horizontal panel layouts. Supply can feed from top or bottom, which simplifies busbar routing in a crowded enclosure. IP20 rating applies only when the distribution board is installed and conductors are connected — that's standard for a panel-mount device; it's not rated for wet or dusty locations. Ambient range from -40 °C to 75 °C covers most indoor industrial and utility environments, including unheated substations. Halogen-free and silicon-free construction is a plus for environments where outgassing from a fault could corrode nearby contacts or optics — think data centers, clean rooms, or food processing lines.