The Schneider Electric A9Z08440 is a 4-pole residual current circuit breaker (RCCB) from the Acti9 ID K range, rated 40 A with 30 mA earth-leakage sensitivity. Voltage-independent tripping means the device clears a fault even if the line voltage is lost, which matters for safety in installations where the neutral could be interrupted.
Rated operational voltage is 380...415 V AC 50 Hz, which covers standard three-phase 400 V line-to-line supplies across Europe and many other regions. The delayed time delay allows coordination with downstream 30 mA instantaneous RCDs, so a fault on a socket circuit trips the local RCD first, not the main switch. Breaking and making capacity is rated Idm 500 A / Im 500 A — sufficient for the prospective fault currents typical in a domestic or small commercial installation, but not for high-fault industrial switchboards.
Installation notes
Neutral is on the left. Terminals accept rigid conductors up to 35 mm² or flexible up to 25 mm², with a stripping length of 14 mm and a tightening torque of 3.5 N.m. The 8 x 9 mm pitch means it occupies 8 modular spaces (72 mm width,) on the rail. Ambient operating temperature range is -5...40 °C; storage range is -30...70 °C. Pollution degree 2 covers normal non-condensing environments.
Designed to EN/IEC 61008-1, the standard for RCCBs. Carries OVE quality label. Rated impulse withstand voltage (Uimp) is 4 kV. The 8/20 µs impulse withstand of 200 A confirms it handles surge currents from lightning or switching without nuisance tripping. Electrical durability is 2000 cycles under AC-1 resistive load; mechanical durability is 5000 cycles.