The Schneider Electric A9N16321 is a 4-pole residual current circuit breaker (RCCB) from the Acti9 xID series, rated at 25 A with 30 mA earth-leakage sensitivity. The Type A-SI (Super Immunised) designation means it handles pulsed DC fault currents from single-phase rectifiers and resists nuisance tripping from high-frequency leakage typical of VFDs and UPS systems — a common requirement on mixed-load panels.
Rated breaking and making capacity is 500 A per EN/IEC 61008-1. That figure governs the RCCB's ability to clear a fault without welding contacts — adequate for downstream protection in a sub-distribution board but not a main incomer; selectivity with an upstream MCB or MCCB needs coordination study. Rated insulation voltage (Ui) is 500 V AC, and rated operational voltage (Ue) is 400–415 V AC — the standard 3-phase + neutral supply in European LV networks. The 4P construction switches all four poles (, L2, L3, N) simultaneously, with neutral on the left side per the connection pitch of 18 mm between phases. The 25 A rating matches a typical feeder for lighting, socket outlets, or small mixed loads. Electrical and mechanical durability are both 4000 cycles — this is a protection device, not a switching contactor; it is designed to sit closed for years and trip only on fault, not for frequent manual operation.
Tunnel terminals accept 1–35 mm² rigid or 1–25 mm² flexible cable; wire stripping length is 14 mm, and tightening torque is 3.5 N·m top or bottom. IP20 rated — suitable for dry indoor enclosures only. The toggle control provides ON, OFF, and fault-trip local signalling, with a contact position indicator and provision for a padlocking device to lock the circuit off for maintenance isolation.
Standards compliance includes EN/IEC 61008-1 and IEC 61008-2-1, with tropicalisation class 2 per IEC 60068-1 (resistance to heat and humidity up to 95% RH at 55 °C).