The Schneider Electric A9N18599 is an add-on residual current device (RCD) from the Acti9 Vigi C120 range. It is a 4-pole unit rated for 125 A continuous current, with a 500 mA earth-leakage sensitivity and Type A-SI (Super Immunised) protection class. Rated operational voltage is 230…415 V AC at 50 Hz, with an insulation voltage of 500 V AC and impulse withstand of 6 kV per IEC 60947-2. The trip is instantaneous — no intentional time delay — so it clears ground faults immediately, which matters for personnel protection in a panel where you want fast disconnect on the outgoing group.
The unit occupies 10 modules of 9 mm pitch — that is 198 mm of rail width. Depth is 73 mm, height 95 mm. Plan for that footprint when laying out a distribution board; it is a wide unit at 4P, so check your enclosure fill factor. Electrical connection to the upstream MCB is by screws. Terminals accept 1…35 mm² flexible or 1…50 mm² rigid cable.
Designed to EN 61009 and IEC/EN 61009-2-1. Ambient operating range is -25…60 °C; storage range -40…60 °C.