The Siemens 5SU1654-0KV32 is a combined residual-current device (RCD) and miniature circuit breaker (MCB) — an FI/LS protector — in a single 1+N-pole module. It integrates type AC residual-current detection (sensitive to sinusoidal AC fault currents) with a B-curve overcurrent trip characteristic rated at 32 A. The 300 mA residual sensitivity (IΔn 300 mA) makes this unit suitable for circuits where a higher trip threshold is needed to avoid nuisance tripping from leakage in equipment or long cable runs — common in distribution sub-mains or circuits feeding multiple loads. The B-curve (B 32 A) trips magnetically between 3 and 5 times rated current (96–160 A), so it protects resistive and general-purpose loads without nuisance trips from moderate inrush. The 70 mm depth (D=70mm) is a standard dimension for DIN-rail mounted RCBOs, fitting most enclosures without overhang.
It serves as a combined earth-leakage and overcurrent protective device for a final circuit — typically lighting, socket outlets, or small appliance circuits in residential, commercial, or light industrial installations where type AC residual detection is sufficient (i.e., no electronic loads generating pulsed or DC fault currents).