The Schneider Electric A9N21388 is a DT40N miniature circuit-breaker from the ProDis range, rated 25 A with a C-curve trip characteristic (magnetic tripping between 5 and 10 times In). Breaking capacity is 6 kA Icn at 400 V AC per EN/IEC 60898-1, and 10 kA Icu at 400–415 V AC per IEC 60947-2 — the dual rating means it satisfies both the household-standard and the industrial-standard for the same installation, giving the specifying engineer headroom for fault-level coordination.
At 25 A and C-curve, this breaker is sized for general-purpose lighting and socket-outlet circuits where inrush from fluorescent ballasts or small motor loads is moderate — the C-curve holds through short-duration surges up to 10x rated current before the magnetic trip operates. The thermal-magnetic trip unit combines a bimetal element for overload protection (time-delayed) with a solenoid for short-circuit protection (instantaneous above the magnetic threshold). This covers most panel-building wiring sizes up to a 25 A circuit.
Integration notes
The toggle handle provides local ON/OFF indication. At 6 pitches of 9 mm (54 mm wide), it occupies three modular spaces in a distribution board. Depth is 78 mm, height 81 mm. IP20 finger-safe terminals per IEC 60529; suitable for enclosed panel use only. Earth-leakage protection requires a separate block — not integrated.