The Schneider Electric A9Y85340 is an add-on residual current device from the Acti9 Vigi iC40 range, designed to clip onto the outgoing side of a compatible Acti9 MCB. It provides earth-leakage protection for a 3-pole circuit rated at 40 A, with a sensitivity of 300 mA and Type A-SI (Super Immunised) waveform discrimination. The unit is voltage-independent, meaning it trips on residual current alone — no auxiliary supply needed — and it operates instantaneously on detection of a fault.
The 40 A rated current (In) means this RCD is sized for a 40 A outgoing circuit — typically feeding a sub-distribution board, a large fixed load, or a group of smaller circuits downstream. The 300 mA sensitivity is a common choice for fire protection or for circuits where nuisance tripping from normal leakage (e.g., long cable runs, electronic loads) must be avoided. Type A-SI (Super Immunised) adds immunity to pulsed DC residual currents and to high-frequency leakage from switched-mode power supplies — a practical choice for modern panels with VFDs, UPSs, or IT equipment. The instantaneous time delay (no intentional delay) means it trips within the standard 300 ms window, so coordination with upstream time-delayed RCDs needs to be checked in selectivity studies.
The 90 mm width matches the standard Acti9 modular enclosure footprint, so it aligns with adjacent MCBs and other modular devices in the same distribution board. Bottom tunnel-type terminals accept 1 to 16 mm² rigid or 1 to 10 mm² flexible conductors; wire stripping length is 14 mm. The unit is IP20 (finger-safe) in the enclosure, IP40 within the modular enclosure — suitable for clean, dry indoor panel environments. Pollution degree 3 per EN/IEC 61009-2-1 means it can tolerate conductive pollution in industrial atmospheres, but not direct washdown.
The unit carries IP20/IP40 protection ratings and is rated for operation at altitudes up to 2000 m and ambient temperatures from -25 °C to +60 °C. Relative humidity tolerance is 95 % at 55 °C.