The Schneider Electric A9D37220 is a 2-pole Acti9 iC60 RCBO — a combined residual-current circuit breaker with overcurrent protection (RCBO) rated 20 A, 30 mA sensitivity, curve B, for 50 Hz AC networks.
The 20 A thermal-magnetic trip (curve B, magnetic threshold 3–5 × In) is sized for resistive and light inductive loads on a final subcircuit — lighting, general sockets, small appliances. The 30 mA earth-leakage sensitivity meets standard personnel protection requirements (IEC 60364). Breaking capacity is 10 kA Icn per EN/IEC 61009-2-1 at 220–240 V AC, with an ultimate Icu of 15 kA per EN/IEC 60947-2 — sufficient for most residential and light commercial distribution boards where the prospective fault current stays under that ceiling. Limitation class 3 (EN/IEC 61009-2-1) means it limits let-through energy under fault conditions, reducing stress on downstream wiring and connected equipment. The 2-pole RCBO protects both poles against overcurrent and earth leakage; the neutral is switched and monitored internally.
Mounts via clip-on to a DIN rail (EN 60715). Occupies 4 × 9 mm pitches = 36 mm width. Tunnel terminals accept 1–35 mm² rigid or 1–25 mm² flexible cable; strip 12 mm, tighten to 2 N·m. Connection pitch is 9 mm between poles — standard for modular DIN-rail devices. IP40 in a distribution enclosure, IP20 bare. The toggle provides ON/OFF and fault-trip local signalling.