The Siemens 5SU9356-8CN40 is a 1+N pole RCBO (residual current circuit breaker with overcurrent protection) rated 40 A, D characteristic, Type A, with a 6 kA breaking capacity. It belongs to the Construction line series, designed for final subcircuit protection in commercial and residential panels where both overcurrent and earth leakage protection are required in a single module. The D characteristic means it tolerates high inrush currents — typical for motor, transformer, or lighting ballast loads — without nuisance tripping, while the Type A residual current detection catches pulsating DC fault currents that a basic AC type would miss.
Panel integration and deployment
Snap-on DIN rail mounting for standard 1+N modular width. The 6 kA breaking capacity covers the majority of domestic and light commercial fault levels; for higher prospective short-circuit currents upstream coordination with a larger MCB or fuse is expected. D-curve magnetic trip (10–20× In) suits loads with high starting currents — think small refrigeration compressors, pumps, or fluorescent banks with electronic ballasts — where a C-curve would nuisance-trip on energisation.