The Schneider Electric A9N18587 is an Acti9 Vigi C120 add-on residual current device (RCD) block, rated 125 A with 300 mA Type A earth-leakage protection. It clips onto a compatible Acti9 MCB via screws, making it a voltage-independent, selective (time-delayed) unit for outgoer group or incomer positions in a distribution board.
The 125 A rated current (In) and 300 mA sensitivity mean this block handles full incoming or submain feeder duty, not just final subcircuits. Type A detects pulsating DC residual currents (common in electronics and variable-speed drives) plus sinusoidal AC — essential for modern mixed-load panels. The selective (S-type) time delay coordinates with downstream RCDs, preventing nuisance tripping on transient earth faults. Rated operational voltage is 230...415 V AC 50/60 Hz, covering single-phase and three-phase networks up to 415 V line-to-line. Mechanical durability of 20000 cycles and operating range -25...60 °C support continuous duty in unconditioned electrical rooms. The clip-on mount fits a 35 mm symmetrical DIN rail; 10 x 9 mm module pitches (198 mm wide) occupy the same footprint as a 4P MCB.
Tunnel-type terminals accept 1...50 mm² rigid or 1...35 mm² flexible conductors; strip length 15 mm, tighten to 3.5 N.m. The block connects to the upstream MCB by screws — no additional busbar needed. IP20 rated, so it lives inside a closed enclosure.