The A9Q16440 is an add-on residual current device (RCD) block from the Schneider Electric Acti9 range, specifically the Vigi iC60 series. It clips onto the outgoing side of an iC60 MCB to add earth leakage protection. Four poles, rated 40 A continuous, with a 500 mA sensitivity and Type AC (sinusoidal AC only) detection. Voltage-independent tripping means it clears a fault even if the line voltage has collapsed — critical for safety in a dead circuit. Mounts via clip-on onto DIN rail (EN/IEC 61009-1 and -2-1). The 63 mm width takes 7 x 9 mm pitches on the rail. Bottom tunnel terminals accept 1 to 35 mm² rigid or 1 to 25 mm² flexible, with a 3.5 N.m torque spec. IP20 body, IP40 inside a modular enclosure — fine for dry indoor panels; not rated for washdown.
That covers single-phase (L-N) and three-phase (L-L) circuits within a 4P assembly. Insulation voltage 500 V AC, impulse withstand 6 kV — coordination with upstream SPDs is straightforward. Earth leakage protection is instantaneous (no intentional delay), Type AC, sensitive to 500 mA. That sensitivity is typical for general distribution or feeder protection where nuisance tripping from leakage in long cable runs or equipment filters needs to be avoided. Not for personnel protection — that calls for 30 mA or lower. The 8/20 µs impulse withstand of 250 A means it survives surge events common on AC mains without false tripping. The -5 °C lower limit means it's not rated for unheated outdoor cabinets in freezing climates — that's a selection gate if the panel sits in a cold warehouse.