The A9N18391 is a Schneider Electric Acti9 C120N miniature circuit breaker rated 80 A at 30 °C with a D tripping curve (magnetic trip threshold 10–14 × In). The 80 A continuous rating at 30 °C is the thermal-magnetic trip unit's baseline; per the datasheet, ambient derating applies above that temperature, so verify the panel's internal temperature if it runs hot. Breaking capacity is listed at three voltage points: 10 kA Icn at 400 V AC per EN/IEC 60898-1, and 20 kA Icu at 220–240 V AC or 6 kA Icu at 440 V AC per EN/IEC 60947-2. The 60947-2 Icu ratings give you the ultimate short-circuit capacity for industrial panel designs where the breaker is used as a disconnect under fault conditions. The 4-pole configuration (4P) switches all four poles simultaneously, with the neutral pole protected. This is the correct choice for three-phase four-wire systems (TN or TT earthing) where you need coordinated isolation and overcurrent protection on all phase conductors plus the neutral. The toggle mechanism provides local ON/OFF indication and a contact position indicator confirms the state of the moving contacts per IEC 60947-2.
The 108 mm width occupies 12 × 9 mm pitches on the rail — plan for that footprint when laying out the distribution board. Tunnel-type terminals accept 1–50 mm² rigid or 1.5–35 mm² flexible conductors; strip length is 15 mm, tightening torque 3.5 N·m. Overvoltage category IV (rated for installations at the origin of the electrical service, before the main distribution panel) confirms it can handle the higher transient overvoltages seen at the service entrance.
Dual certification to EN/IEC 60898-1 (the residential/light-commercial MCB standard) and EN/IEC 60947-2 (the industrial circuit-breaker standard) means this breaker qualifies for both domestic distribution boards and industrial panel designs. The 60947-2 certification also includes the suitability-for-isolation marking — the breaker can serve as a visible-break disconnect in the open position, per the contact position indicator.