What this RCBO is and what it does
The Siemens SENTRON 5SU1674-7FK82 is a 4-pole RCBO (residual current circuit breaker with overcurrent protection) in the Super resistant K design, rated 125 A at AC with a C tripping characteristic and a 300 mA type B+ residual current trip. Type B+ residual current detection covers smooth DC, pulsating DC, and high-frequency AC fault currents — meaning it handles the leakage profiles from VFDs, UPS systems, and EV chargers that a standard AC or A type would miss. Rated breaking capacity is 10 kA per both EN 60898 and IEC 60947-2, so it interrupts fault currents up to that level without upstream coordination issues in a typical distribution board. The 125 A rating applies at 30 °C; derate to 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 — the thermal curve governs real-world loading in a warm enclosure.
Panel fit and mounting
Occupies 11 modular width units (MWU) on a DIN rail; the housing is 198 mm wide, 90 mm high, and 77 mm deep, with an installation depth of 70 mm behind the panel face. Mounting position is unrestricted, and the supply cord can enter from either the top or bottom — useful when retrofitting into an existing board with fixed busbar routing. IP20 rating applies once the distribution board is installed with connected conductors; touch protection is built in, and the overvoltage category is III (fixed installation, not downstream socket outlets).