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 6 kA breaking capacity (per IEC 60898) suits it for domestic or light commercial distribution boards where the prospective short-circuit current stays under that threshold.
What the ratings mean for fit
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 Type AC designation means it detects sinusoidal AC residual currents only; if the load includes rectifiers, VFDs, or switched-mode supplies that generate pulsed or high-frequency DC fault currents, a Type A or Type F RCD would be needed instead. 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.
Panel integration note
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.