The Siemens 5SU1354-7FM20 is a 1-pole-plus-neutral RCBO (residual current circuit breaker with overcurrent protection) rated for 20 A at 230 V AC with a 10 kA breaking capacity. It combines a type A residual current device (30 mA trip threshold) with a C-characteristic MCB in a single DIN-rail module — one unit covers both earth-leakage and overload/short-circuit protection for a final subcircuit.
The C-characteristic (C-Char) means the magnetic trip operates at 5–10× In (100–200 A for this 20 A unit), so it tolerates motor inrush and capacitive loads without nuisance tripping while still clearing hard faults quickly. Type A residual current detection handles pulsating DC fault currents (rectified waveforms from electronics, variable-speed drives, LED drivers) in addition to sinusoidal AC — essential for modern circuits where non-linear loads are present.