The Schneider Electric A9N21537 is an iDPN miniature circuit breaker from the Clario range, rated 16 A with a B-curve trip characteristic (magnetic trip between 3 and 5 times In). Breaking capacity is 4500 A Icn at 230 V AC, 50/60 Hz — sufficient for most domestic and small commercial service entrances where the prospective fault current stays under that threshold. The thermal-magnetic trip unit handles overloads and short-circuits without external auxiliary power.
Clip-on mounting to DIN rail (EN 60715) — 18 mm width per pole, so this 1P+N unit occupies 2 modules (36 mm). Depth is 78 mm, height 81 mm. Tunnel terminals accept up to 16 mm² rigid or 10 mm² flexible on both line and load sides; tighten to 2 N·m with 13 mm strip length. IP20 finger-safe terminals suit enclosed panel use. Tropicalisation class 2 per IEC 60068-1 handles 95 % RH at 55 °C without derating.