The Siemens 5SU1356-0DV20 is an FI/LS combination unit — a residual-current device (RCD) and miniature circuit breaker (MCB) in one 1+N-pole module. It carries a B-curve 20 A overcurrent trip for general-purpose branch-circuit protection, combined with a 30 mA Type AC residual-current trip for personnel protection against sinusoidal AC fault currents.
The 30 mA trip threshold is the standard for socket-outlet circuits in residential and commercial installations per IEC 60364 — it catches body currents before ventricular fibrillation becomes likely. The B-curve 20 A overcurrent characteristic trips between 3× and 5× In (60–100 A), so it handles inrush from resistive and lightly inductive loads like lighting banks, small motors, or heating elements without nuisance tripping.
The 70 mm depth (D=70mm) and 1+N-pole form factor fit standard DIN-rail enclosures. The pigtail connection means the neutral tail is factory-attached — no separate neutral bar connection needed on the load side, which simplifies wiring in a distribution board. Verify the busbar pitch matches the module width before panel assembly.