The Schneider Electric A9R31240 is an Acti9 iID residual current circuit breaker (RCCB) — a 2-pole, 40 A device with 30 mA earth-leakage sensitivity, built to EN/IEC 61008-1. It clips onto a DIN rail, occupies 4 x 9 mm pitches (36 mm wide), and is rated for 220...240 V AC at 50/60 Hz. The Type A-SI (Super Immunised) classification means it handles pulsed DC fault currents and resists nuisance tripping from transient surges or high-frequency leakage — a common fit for mixed-load final circuits with electronics, VFDs, or LED drivers.
40 A rated current and 30 mA sensitivity are the two numbers that decide the circuit it protects. The 40 A matches a 40 A MCB upstream or a 40 A rated submain; the 30 mA trip threshold covers socket-outlet and general-purpose circuits where personnel protection is required. The Type A-SI waveform recognition catches smooth DC residual currents up to 6 mA plus pulsed DC — essential where single-phase rectified loads are present. The instantaneous trip (no intentional time delay) means it clears a ground fault within the cycle, so it's not suited for selectivity with downstream RCDs unless those are time-delayed (Type S). Rated breaking capacity Idm 1500 A and Im 1500 A means the RCCB can safely interrupt a fault current up to 1500 A at rated voltage — adequate for most final circuits fed from a distribution board with a 10 kA or 16 kA upstream MCB. The 6 kV impulse withstand (Uimp) confirms it survives lightning-induced surges without internal flashover. Mechanical durability of 20000 cycles and electrical durability of 15000 cycles (AC-1 resistive load) — that's the expected life under normal switching. For a fixed RCCB that rarely sees manual operation, mechanical endurance is academic; the electrical figure matters if the device is used as a functional switch for a resistive load. In practice, an RCCB this size is switched maybe a few hundred times over its service life, so the endurance rating is not a constraint.
Clip-on mounting to DIN rail, neutral on the left. Tightening torque 3.5 N.m top or bottom. Wire strip length 14 mm. IP20 finger-safe terminals; IP40 in a modular enclosure. The padlocking device (sold separately) locks the toggle in OFF position for lockout/tagout.