What this RCBO is and what the ratings mean
The Siemens 5SU1354-6KV25 is a combined residual-current device and miniature circuit breaker (RCBO) in a single 1+N-pole module — Type A sensitivity for pulsating DC and AC residual currents, 30 mA trip threshold, 10 kA breaking capacity per IEC/EN 61009, B-curve 25 A overcurrent protection. The 30 mA rating means it protects against lethal shock in standard domestic and commercial final circuits; Type A ensures it catches the pulsed DC residuals from single-phase rectified loads (washing machines, LED drivers, IT equipment) that a Type AC would miss. The B-curve 25 A trips magnetically at 3–5× In (75–125 A) for short-circuit protection of resistive or lightly inductive loads — sized for lighting, socket outlets, or small heater circuits up to 25 A.