The Schneider Electric A9N21371 is a Prodis DT40N miniature circuit breaker rated 1 A with a D-curve trip characteristic, 1P+N poles, and a clip-on DIN-rail mount for distribution panels. Rated 6000 A Icn at 230 V AC per EN/IEC 60898-1 and 10 kA Icu at 230–240 V AC per IEC 60947-2, this MCB covers both residential and industrial coordination requirements — the 10 kA rating is what you use for the upstream fault-withstand calculation in a commercial panel.
At 1 A rated current, this is a low-current branch or control-circuit protector — sized for a small transformer primary, a contactor coil supply, or a PLC power feed, not a general lighting circuit. Thermal-magnetic trip technology combines a bimetal for overload protection (time-delayed) with a solenoid for short-circuit protection (instantaneous above the magnetic threshold). Dual certification to EN/IEC 60898-1 (domestic MCB standard) and EN/IEC 60947-2 (industrial CB standard) means this part can be specified in either a household consumer unit or an industrial distribution board — the 10 kA Icu rating under 60947-2 is the one that governs for industrial coordination studies. Pollution degree 3 per IEC 60947-2 confirms suitability for conductive-dust environments typical in industrial enclosures, not just clean residential panels. IP20 finger-safe terminals are standard for panel-mounted breakers; the enclosure provides the higher IP rating.
Physical integration and wiring
Clip-on mount to standard 35 mm DIN rail; occupies 2 × 9 mm pitches (18 mm width) for the 1P+N form factor. Tunnel-type terminals accept 0.33–10 mm² flexible or 0.75–16 mm² rigid upstream and downstream; wire strip length 13 mm, tightening torque 2 N·m. Toggle control with ON/OFF local indication; neutral position is left per the 1P+N arrangement.