The Schneider Electric A9N21461 is a Vigi DT40 add-on residual current device from the Prodis range — a 3-pole, 25 A, 300 mA Type AC module that clips onto a DIN rail alongside a compatible MCB to provide earth-leakage protection for outgoing circuits. Rated 400 V AC phase-to-phase at 50 Hz, it uses voltage-independent residual current tripping technology with instantaneous response — no auxiliary supply needed, so it drops out cleanly even if the neutral is lost upstream. The IP20 finger-safe enclosure (IEC 60529) and pollution degree 3 rating make it suitable for standard distribution panelboards and enclosures where it lives behind a locked door or cover — not for wet or outdoor locations.
25 A rated current and 300 mA earth-leakage sensitivity define the load and protection envelope. Rated impulse withstand voltage of 6 kV and insulation voltage of 400 V conform to EN 61009-1, which certifies it as a combined overcurrent and residual current device for household and similar installations. The 6 kV impulse rating means it survives typical mains-borne transients without flashover. Clip-on mounting on DIN rail and screw-terminal connections for the MCB interface mean it integrates into a standard panel layout — 4 modules of 9 mm pitch, so it occupies 36 mm of DIN-rail width. Cable terminals accept 0.75…16 mm² rigid or 0.33…10 mm² flexible downstream.
Operating temperature range -5…60 °C and storage range -40…60 °C with 95 % relative humidity at 55 °C and tropicalisation level 2 per IEC 60068-1 — this unit handles warm, humid panel environments typical of Southeast Asia or coastal installations without condensation protection. Compliant with EN 61009-1 and EN 61009-2-1. No UL, CSA, or UKCA mark is listed in the evidence — verify local acceptance before specifying for North American or UK projects.