The Schneider Electric A9R24492 is an Acti9 RCCB-ID residual current circuit breaker (RCCB) — a 4-pole unit rated for 125 A continuous current with a 300 mA Type A earth-leakage sensitivity. It operates on 400 V AC, 50 Hz networks and is built to IEC/EN 61008-1 and IEC/EN 61008-2-1 standards, so it meets the core European and international requirements for residual current protection in commercial and industrial distribution boards.
The 125 A In rating tells you this RCCB handles the full load of a heavy submain or a large feeder — think main switchboard outgoing supplying a workshop, a pump house, or a lighting distribution board. It is not a final-circuit device; you size it for the upstream protection, not the last socket. The 300 mA sensitivity is an earth-leakage threshold, not a short-circuit trip. It is designed for equipment protection and fire prevention, not personal shock protection. That matters when you are laying out a panel: the busbar or wiring order has to match the neutral position. The 18 mm phase-to-phase pitch keeps it compatible with standard Acti9 busbar systems. Rated breaking and making capacity is 1250 A at both 400 V and 230 V — that is the short-circuit current it can safely interrupt.
The fixed mounting mode and tunnel-type terminals accept a wide range of conductors: up to 50 mm² rigid or 35 mm² flexible per pole, with a wire stripping length of 11 mm and a tightening torque of 3 N·m. The terminal layout accommodates two cables per side up to 16 mm², which is handy for looping through to downstream devices. The device occupies 8 modules of 9 mm pitch, so it takes up 72 mm of DIN-rail width. That is standard for a 4P 125 A RCCB in the Acti9 range — plan your enclosure rail length accordingly. It is padlockable for lockout/tagout, and the red/green trip indicator gives a clear visual status without needing to meter the load side. IP20 protection on the device body (finger-safe) and IP40 in a modular enclosure means it is fine inside a clean indoor panel.