The Schneider Electric A9Z83440 is a 4-pole residual current circuit breaker (RCCB) from the Acti9 iID family, rated 40 A with 100 mA earth-leakage sensitivity. The selective (time-delayed) Type A characteristic means it discriminates from downstream RCCBs, so a fault on a branch doesn't take the whole board dark. Voltage-independent tripping keeps it functional even if the neutral is lost upstream.
The 100 mA sensitivity is a selective threshold — it's set above the 30 mA personal-protection level to avoid nuisance tripping from cable capacitance or equipment leakage, while still providing fire protection. Type A detection catches pulsating DC residual currents (common from single-phase rectifiers, VFDs, LED drivers) that a plain AC type would miss.
Listed as current production. It is a standard catalogue item from Schneider.
Clip-on DIN rail mount, 4-pole wide at 72 mm (8 x 9 mm pitches). Neutral on the left. Wire strip length 14 mm, tightening torque 3.5 N.m. IP20 finger-safe on the front face; IP40 within a modular enclosure.
Compliance and standards coverage
The 8/20 µs impulse withstand of 3000 A (per the same standard) covers surge immunity from lightning-induced transients. Rated insulation voltage 500 V AC, impulse withstand 6 kV. The selective time-delay characteristic is defined within the standard, not a custom curve — so coordination with upstream and downstream devices is predictable.