The Schneider Electric A9Z64425 is a 4-pole Acti9 iID residual current circuit breaker (RCCB) rated for 25 A continuous current with a 300 mA earth-leakage sensitivity. It's a Type B-SI (Super Immunised) device, meaning it handles smooth DC fault currents and high-frequency AC waveforms that trip standard types — think variable-speed drives, UPS feeds, or photovoltaic inverters where the leakage signature isn't a clean 50 Hz sine wave.
The 25 A rating and 300 mA sensitivity tell you this RCCB sits on a submain or large final circuit — not a lighting branch. The 300 mA threshold is for equipment protection or fire prevention, not personnel shock protection (that's 30 mA). Type B-SI is the key differentiator: it detects smooth DC residual currents up to the rated frequency and is immune to nuisance tripping from high-frequency leakage generated by drives or PV inverters. That SI (Super Immunised) suffix means it withstands 8/20 µs impulse surges up to 3 kA without tripping, so you won't get false trips from lightning-induced surges on the line side.
Neutral is on the left. IP20 body, IP40 inside a modular enclosure. Overvoltage category IV suits it for main incomer positions, not just downstream sub-distribution.
Lifecycle status is current — this is an active Schneider catalog item, not a phase-out or NRND line. It's part of the Acti9 range, which is the current-generation modular DIN-rail platform. Standards compliance includes IEC 61008-2-1, IEC/EN 62423, and EN 61008-2-1, with quality marks VDE, NF, IMQ, and KEMA.