MCB for distribution panels — dual-standard breaking capacity
The Schneider Electric A9N21406 is a ProDis DT40 miniature circuit breaker rated 16 A with a C trip curve, 3 protected poles plus neutral (3P+N). It clips onto a DIN rail and is intended for distribution applications in residential or light commercial panels. Breaking capacity is dual-rated: 6000 A Icn at 400 V AC per EN/IEC 60898-1 for standard MCB duty, and 10 kA Icu at 400–415 V AC per IEC 60947-2 for industrial coordination. The higher Icu rating means this breaker can safely interrupt fault currents up to 10 kA without upstream backup — useful when the panel SCCR requirement exceeds 6 kA. The thermal-magnetic trip unit (curve C) triggers magnetically between 5 and 10 times In, so it handles moderate inrush from motor starters or transformers without nuisance tripping, while still clearing short circuits fast enough for most distribution feeders.
Panel integration and wiring
Mounts via clip-on to a standard 35 mm DIN rail. Occupies 6 x 9 mm pitches (54 mm wide) — fits alongside other ProDis or Acti9 units in a multi-row enclosure. Neutral is on the left, toggle control on the front with ON/OFF indication. Tunnel terminals accept up to 16 mm² rigid or 10 mm² flexible on both upstream and downstream sides. Wire stripping length is 13 mm; tightening torque is 2 N·m. IP20 finger-safe protection on the front face.