The Siemens 5SU1356-1KK08 is a SENTRON 5SU1 series RCBO — a combined residual-current circuit breaker with overcurrent protection, rated 8 A at AC with a C tripping characteristic and 6 kA breaking capacity per EN 60898. It occupies 2 MW (36 mm wide) on a DIN rail, 1P+N configuration, and is designed for instantaneous fault current detection (AC type). The C-curve means it trips between 5× and 10× rated current — suited for circuits with moderate inrush, like small motor or lighting loads. The 6 kA rated short-circuit capacity per EN 60898 covers most residential and light commercial distribution boards.
Thermal derating and conductor sizing
Rated current derates with ambient temperature: 8 A at 30 °C, 7.52 A at 40 °C, 7.28 A at 45 °C, 6.96 A at 50 °C, 6.48 A at 55 °C and 60 °C, 6.16 A at 65 °C, and 5.84 A at 70 °C. If the distribution board runs warm — common in crowded enclosures — the effective ampacity drops; size upstream protection accordingly. Terminals accept solid or stranded conductors from 0.75 mm² up to 35 mm², covering most branch-circuit wiring sizes. Power loss at rated load is 2.4 W maximum.
Mounting and environment
Snap-on mounting for 35 mm DIN rail, any position. Installation depth is 70 mm; overall depth including terminals is 77 mm. IP20 rating applies when installed in a distribution board with conductors connected — not for exposed or wet locations. Ambient operating range is -25 to +55 °C; storage range is -40 to +75 °C. Halogen-free and silicon-free construction. Supply connection can be from top or bottom.