The A9Y85740: The 300 mA sensitivity is the trip threshold for earth leakage. This is not a 30 mA personal-protection device — it is sized for equipment protection or fire prevention on circuits where nuisance tripping from normal leakage (long cable runs, industrial loads) would shut down production. The Type A-SI (Super Immunised) designation means it handles pulsed DC fault currents (rectifier-fed loads) and resists unwanted tripping from high-frequency leakage or transient surges common on industrial lines. Voltage-independent tripping means the RCD operates on the residual current itself, not on the line voltage — it will still trip if the neutral is lost upstream. Rated insulation voltage is 440 V AC, and the operational voltage is 400 V AC — standard for a 3-phase + N distribution board in a 400/230 V system. For a distribution board that sees infrequent manual operation, this is a long service life.
Neutral is on the left. The device is an add-on RCD — it screws directly to the outgoing side of a compatible Acti9 MCB (the Vigi iC40 mates with the iC40 range of miniature circuit breakers). Tunnel-type terminals accept 1 to 16 mm² rigid or 1 to 10 mm² flexible cable; strip length 14 mm, tightening torque 2 N.m. The IP20 body is standard for enclosed distribution boards; the modular enclosure achieves IP40 when installed in a panel.