The A9N18560 is an add-on residual current device (RCD) from the Schneider Electric Acti9 Vigi C120 range, designed to clip onto the outgoing side of a compatible MCB or MCCB to provide earth-leakage protection. It is rated for 125 A continuous current with a 300 mA Type A-SI (Super Immunised) sensitivity and a selective (time-delayed) trip characteristic, making it suitable for downstream coordination in distribution boards where nuisance tripping from transient leakage must be avoided.
The 125 A rated current sets the maximum continuous load this RCD can carry — sized for a main incomer or large subfeed in a commercial or industrial panel. The 300 mA sensitivity is above the 30 mA required for personal shock protection; this unit is intended for fire protection and equipment protection, not direct personnel protection. The Type A-SI classification means it detects sinusoidal AC and pulsating DC residual currents, and the 'Super Immunised' suffix indicates a higher immunity to high-frequency leakage from VFDs or UPS systems — a common source of nuisance trips in modern panels. The selective time delay allows coordination with downstream 30 mA RCDs, so only the faulted branch trips first.
The 4P (4-pole) form factor occupies 10 x 9 mm pitches, so 90 mm of DIN rail width. Tunnel-type terminals accept 1…35 mm² flexible or 1…50 mm² rigid cable; strip length 15 mm, tighten to 3.5 N·m. IP20 finger-safe for enclosed panel use only.