The Schneider Electric A9R16492 is a 4-pole residual current circuit breaker (RCCB) from the Acti9 range, rated 125 A at 400 V AC, 50 Hz. It provides earth-leakage protection for outgoing circuits in a distribution board, tripping instantaneously when leakage current exceeds 500 mA.
At 125 A and 400 V, this RCCB handles the full incoming supply for a large sub-distribution board or a high-load outgoer — think a commercial kitchen, a workshop, or a bank of HVAC units. The 500 mA sensitivity is a deliberate choice: it's above the 30 mA threshold used for personal shock protection, so it's intended for equipment protection or fire prevention, not direct human contact. The instantaneous trip (no intentional delay) means it clears faults fast, but selectivity with downstream 30 mA RCDs requires careful coordination — the 500 mA device will trip first on a high-impedance fault. Breaking capacity is rated at Im = 1250 A at both 400 V and 230 V, per IEC/EN 61008-1 and 61008-2-1. The 8/20 µs impulse withstand of 250 A means it survives surge currents from lightning or switching transients without nuisance tripping. The storage temperature range of -40 to 85 °C covers most warehouse and transport conditions, though the operating ambient during service will be lower.
The 4-pole body occupies 8 x 9 mm pitches (72 mm total width), with the neutral on the left. Depth is 76 mm, height 86 mm — check gland plate clearance if the enclosure is shallow. Tunnel-type terminals accept up to 50 mm² rigid or 35 mm² flexible cable; wire stripping length is 11 mm, tightening torque 3 N·m. The IP20 body is fine for enclosed panels; the modular enclosure option gives IP40 for the front face. Padlockable toggle and a red/green trip indicator give clear local status — the contact position indicator shows whether the RCCB is on, off, or tripped, which speeds fault isolation on a multi-way board.