The Schneider Electric A9N21466 is a Prodis Vigi DT40 add-on residual current device — a 3-pole, 40 A unit with 30 mA earth-leakage sensitivity, designed to clip onto the outgoing side of a compatible MCB. It's voltage-independent, meaning the trip mechanism doesn't rely on the line voltage to detect a fault; it'll still clear a ground leak even if the phase voltage collapses. Type A-SI (Super Immunised) protection handles pulsed DC fault currents and resists nuisance tripping from high-frequency harmonics or switching transients common on modern electronic loads.
This part is officially obsolete per the manufacturer's lifecycle record. There's no listed direct successor order code in the evidence, so a parametric cross-reference is the route forward.
Rated at 40 A and 400 V AC phase-to-phase, it's sized for a 3-phase outgoing feeder on a 50 Hz network. The 30 mA sensitivity is standard for personnel protection (shock hazard) per most wiring codes. Pollution degree 3 (conforming to EN 61009-1) means it's rated for the conductive-dust and humidity environment you'd find in an industrial panel, not a clean office. The IP20 finger-safe housing is fine inside a closed enclosure — no washdown rating, so mount it behind a sealed gland plate if the panel sees hosedown.
Clip-on mounting to DIN rail, 3-pole width. The 54 mm width and 69 mm depth fit a standard 4-module DIN space (9 mm pitch per pole). Terminal capacity accepts 0.75…16 mm² rigid or 0.33…10 mm² flexible cable; strip 13 mm, torque to 2 N·m. Electrical connection to the upstream MCB is by screws — it's a mechanical add-on, not a standalone device, so verify the MCB's terminal interface is compatible.
Environmental and durability specs
Rated for -25…60 °C operating ambient, -40…60 °C storage. 95 % RH at 55 °C with tropicalisation level 2 per IEC 60068-1 — that passes the 28-day damp-heat cycle, so it's fine for coastal or high-humidity plant rooms. Electrical durability is 10,000 cycles, which is typical for a residual current block on a distribution feeder. Impulse withstand is 6 kV per EN 61009-1, covering most surge environments up to 2000 m altitude.