The Siemens SENTRON 5SM3324-4KK14 is a 2-pole residual current operated circuit breaker (RCCB) rated at 40 A with 30 mA sensitivity, designed for 230 V AC single-phase circuits. It's a Type B+ device, meaning it catches AC sinusoidal faults, pulsating DC faults, and smooth DC fault currents up to the rated sensitivity — the kind you get from variable-speed drives, UPS systems, or PV inverters. The short-time delayed characteristic (S-type) gives it selectivity with downstream devices, so a ground fault on a branch doesn't take out the whole panel.
The 40 A rated current (In) handles the full load of a typical submain feeding a small distribution board or a heavy single-phase load like a commercial oven or air handler. The 30 mA residual sensitivity is the standard for personnel protection (shock hazard) per IEC 60364. Type B+ extends coverage to smooth DC — critical when the downstream loads include rectifiers or drives that can generate DC fault currents a standard AC type would miss.
Supply voltage can be fed from top or bottom; the SIGRES function (switched-off state indication) works from the bottom feed as noted. Silicon-free construction suits environments where silicone outgassing can contaminate contacts or optics.