The Siemens 5SU1324-0KK82 is a SENTRON RCBO — a combined residual-current circuit breaker and overcurrent protection device in one 6.5-module-wide housing. It's a 2-pole unit rated 125 A at 30 °C, with a 30 mA AC-type residual-current trip and a B tripping characteristic. Breaking capacity is 10 kA per EN 60898 and IEC 60947-2. That 10 kA SCCR at 400 V means it safely interrupts faults up to that level without cascading upstream — important for panel coordination studies.
Temperature derating and real-world current
The 125 A rating holds at 30 °C ambient. Above that, the device derates linearly: 115.62 A at 40 °C, 111.25 A at 45 °C, 106.25 A at 50 °C, 101.25 A at 55 °C, and 96.25 A at 60 °C. If your panel ambient runs 50 °C, you're limited to 106.25 A continuous — that's the number to put in your load schedule, not the 125 A headline. The operating range spans -40 °C to 75 °C, so it handles cold storage or rooftop enclosures without issue.
Mounting and integration
Mounts on DIN rail in any position — top or bottom feed accepted. Installation depth is 70 mm. The housing is IP20 once installed in a distribution board with conductors connected. Pollution degree 2 and overvoltage category III suit it for fixed-installation panels in commercial or light industrial settings. Halogen-free and silicon-free construction matters for environments where off-gassing or contamination is a concern (clean rooms, food processing).