The Schneider Electric A9V21425 is an Acti9 Vigi iC60 add-on residual current device — a 4-pole, 25 A, 30 mA Type A RCD block that clips onto the outgoing side of a compatible iC60 MCB. It's voltage-independent, so it trips on residual current even if the line voltage drops out, and it's instantaneous — no intentional delay. The 30 mA sensitivity covers standard personnel protection (shock risk) and Type A catches pulsating DC faults from single-phase rectified loads like switching power supplies or variable-speed drives.
This part is obsolete per the manufacturer's lifecycle record. If you're planning a new panel or a revision, check whether the active Acti9 Vigi iC60 range still carries a direct functional equivalent; the form factor and mounting (clip-on DIN rail, 6 x 9 mm pitches wide) are standard for the series.
The 4-pole block occupies six 9 mm modular pitches (54 mm wide). Bottom tunnel terminals accept 1...25 mm² rigid or 1...16 mm² flexible cable; tighten to 2 N·m. The electrical connection to the MCB is by screws, so you need a screwdriver to lock the phase/neutral bus bars between the breaker and the RCD. IP20 on the block itself, IP40 inside a modular enclosure.
Compliant with IEC 61009-1 and EN 61009-1 (RCBO standard for RCD + overcurrent combined, though this is an add-on block, not a combined unit). Pollution degree 3 per IEC 60947-2. Impulse withstand: 8/20 µs, 250 A per IEC 61009-1. Local trip indicator on the front for quick visual fault identification — saves time during commissioning or troubleshooting.