What it is and what it does
The Siemens 5SU9304-0KK10 is a 2-pole RCBO — a combined residual-current device and miniature circuit breaker in a single 18 mm-wide module. It belongs to the SENTRON series and is rated for 10 A at 50/60 Hz with a B-curve tripping characteristic, meaning it protects against overcurrents and short circuits while also detecting earth leakage currents down to 30 mA. The 10 kA breaking capacity per EN 60898 and IEC 60947-2 is sufficient for most residential and light commercial distribution boards, and the instantaneous design (no time delay) means it trips without intentional delay on residual faults.
Mounting and integration
Snaps onto standard 35 mm DIN rail and occupies one modular width (18 mm). Installation depth is 70 mm, with an overall depth of 77 mm including the housing. The supply can enter from either top or bottom, and the mounting position is unrestricted — any orientation works. Touch protection is built in. Rated for overvoltage category III and pollution degree 2, which covers fixed-installation distribution panels in dry, non-conductive environments.
Thermal derating and ambient limits
The 10 A rating holds at 30 °C ambient. At 40 °C it derates to 9.4 A, at 45 °C to 9.1 A, at 50 °C to 8.7 A, and at 55 °C to 8.1 A. The operating range spans -40 °C to +75 °C, so it handles both cold storage areas and warm enclosures. Halogen-free and silicon-free construction matters for environments sensitive to outgassing — clean rooms, medical facilities, or sealed enclosures where corrosion on contacts is a concern.