The Schneider Electric A9KR14225BQ is an Acti9 ID K residual current circuit breaker (RCCB) — a voltage-independent Type AC device rated for 25 A continuous load with a 300 mA earth-leakage trip threshold, 2-pole (2P), for 220-240 V AC 50 Hz networks.
The 300 mA sensitivity is the key spec for this RCCB — it's an instantaneous trip (no time delay) designed for group incomer protection, not individual circuit-level shock protection. That means it catches earth faults on a sub-distribution board or a bank of circuits, but won't nuisance-trip on normal cable leakage. The insulation voltage (Ui) is 440 V AC, so it's suitable for 240/415 V three-phase systems when used as a single-pole-per-phase device, though the operational voltage (Ue) for this specific variant is 220-240 V AC. Pollution degree 2 (non-conductive pollution only) is standard for enclosed distribution boards. Mechanical durability is 5000 cycles, electrical durability (AC-1 resistive load) is 4000 cycles — that's a residential/commercial duty cycle, not industrial high-switching applications.
Clip-on mounting to DIN rail, neutral on the left. Terminals accept Biconnect top or bottom: 1-35 mm² rigid or 1-25 mm² flexible. Wire stripping length is 14 mm, tightening torque 3.5 N.m. That's enough for a 6 mm² or 10 mm² incoming feed on a sub-main board. The 4-module width (36 mm) is the standard RCCB footprint — no surprises on the gland plate.