The Schneider Electric A9D55720 is a 20 A, 30 mA residual current circuit breaker with overcurrent protection (RCBO) from the Acti9 DPN Vigi range, combining a Curve B MCB and an RCD in a single 3P+N module. The 20 A rated current (In) governs the continuous load it can carry in a distribution board — sized for lighting, general-purpose socket circuits, or small motor loads where the full-load current stays under 16 A for headroom. The 30 mA earth-leakage sensitivity provides personnel protection against direct contact, compliant with the requirements of IEC 60364 for final circuits in residential and commercial installations. Curve B (magnetic trip at 3 to 5 x In, so 60 to 100 A) suits predominantly resistive loads or short cable runs where inrush is low — common for lighting and socket-outlet circuits where the MCB should not nuisance-trip on a cold filament or capacitor bank. The 6 kA breaking capacity (Icn at 380...415 V AC, 50/60 Hz) is the maximum prospective fault current the device can safely interrupt under standard test conditions per EN/IEC 61009-2-1. The limitation class 3 (energy let-through) means it restricts the I²t pass-through energy, helping with downstream coordination and reducing arc-flash stress on the connected wiring.
The module occupies 10 x 9 mm pitches (90 mm width) — a 3P+N RCBO in a single-width housing that saves one module position compared to a separate MCB + RCD pair. Tunnel-type terminals accept 0.75 to 16 mm² rigid or 0.33 to 10 mm² flexible conductors; strip length is 15 mm, tightening torque 2 N.m.