The Siemens SENTRON 5SV3321-4 is a 2-pole residual current circuit breaker (RCCB), Type B, short-time delayed, rated 16 A with a 30 mA trip threshold on 230 V AC. That Type B classification means it catches smooth DC fault currents up to the rated residual — the sort of leakage you get from VFDs, UPS systems, or PV inverters — not just sinusoidal AC. The short-time delay (SIGRES function) lets it ride out transient earth faults that would nuisance-trip a standard instantaneous RCCB, so it's a fit for circuits with surge suppressors or motor drives that generate brief leakage spikes.
Ratings and deployment
Rated short-circuit current withstand is 10 kA, which means it can interrupt a fault up to that level without welding its contacts — sized for residential or light commercial distribution boards where the prospective fault current stays under that ceiling. The 2-pole design switches both line and neutral, and the supply can land on top or bottom terminals; the SIGRES function keeps the neutral switched even in the off state. Mounts on DIN rail (REG) per, takes 4 modular width units (72 mm wide), and fits any mounting position. IP20 with conductors connected — standard for enclosed distribution boards, not for wet locations.