What this RCBO is and where it fits
The Siemens 5SU1374-7DK81 is a 4-pole RCBO from the SENTRON 5SU1 series, combining overcurrent protection and residual current detection in a single 11-module-wide unit. It's designed for 50 Hz AC networks and rated 100 A at 30 °C ambient, with a C tripping characteristic for moderate inrush loads like motor circuits and distribution feeders. The Type B+ fault current detection handles AC, pulsating DC, smooth DC, and high-frequency residual currents — covering modern electronics, VFDs, and UPS systems that generate complex leakage profiles. The 10 kA breaking capacity per both EN 60898 and IEC 60947-2 means it safely interrupts fault currents up to that level without cascading upstream.
Thermal derating and conductor sizing
The 100 A rating holds only at 30 °C. At 40 °C it derates to 92.5 A, at 50 °C to 85 A, and at 60 °C to 77 A. In a warm panel near other heat sources, the effective continuous current is lower than the nameplate — plan the load accordingly. The terminals accept solid or stranded conductors from 6 to 50 mm², covering most distribution cable sizes up to the full rating.
Panel fit and environmental limits
The RCBO occupies 11 width units (198 mm) on a DIN rail, with a depth of 77 mm and an installation depth of 70 mm. Mounting position is any orientation, and the supply can enter from either top or bottom. The IP20 rating applies only when installed in a distribution board with conductors connected — this is a panel-mount component, not a standalone enclosure. Ambient operating range is -25 to +55 °C; storage range extends to -40 to +75 °C.