The Schneider Electric A9W21425 is an add-on residual current device (RCD) from the Acti9 Vigi iC60 range, designed to clip onto the side of an iC60 MCB. It provides earth leakage protection for the downstream circuit, tripping the connected breaker when it detects a fault current to ground. Rated at 25 A and 400/415 V AC, this 4-pole unit is intended for three-phase outgoing circuits in distribution boards. The 30 mA sensitivity covers standard personnel protection (shock) and fire prevention, while the Type A designation means it responds to both sinusoidal AC and pulsating DC residual currents — common on circuits with single-phase rectifiers, switch-mode supplies, or variable-speed drives. The trip is instantaneous — no intentional time delay — so it clears ground faults immediately. That makes it suitable for final subcircuits where fast disconnection is required, but coordination with upstream time-delayed RCDs needs checking if selectivity is a concern.
The RCD connects to the iC60 MCB via screws on the load side, using tunnel-type terminals that accept 1 to 25 mm² rigid or 1 to 16 mm² flexible cable. IP20 rated on the body, IP40 inside a modular enclosure.
Designed and tested to IEC 61009-1 and EN 61009-1 — the harmonized standards for RCDs with integral overcurrent protection (though this is an add-on unit, it's certified to the same family standard). Rated impulse withstand voltage 6 kV, insulation voltage 500 V AC.