The Schneider Electric A9KR15240 is a 2-pole residual current circuit breaker (RCCB) from the Acti9 ID K family, rated 40 A with 100 mA earth-leakage sensitivity. The 100 mA sensitivity means it guards against earth faults that could cause fire or equipment damage, not personnel shock (that needs 30 mA or lower). Type AC detection handles sinusoidal AC residual currents; for pulsed DC or mixed-frequency faults you'd step to Type A or B, but for standard lighting, heating, and socket-outlet groups in an AC network at 50 Hz this is the right call.
Rated insulation voltage is 440 V AC, so the internal clearance and creepage are sized for a 440 V system even though the coil sees 240 V; that headroom matters if the RCCB sits downstream of a 400/230 V three-phase distribution where a phase-to-earth fault could stress the insulation. Breaking capacity is 500 A (Idm and Im both 500 A,) — modest, but typical for an RCCB that relies on an upstream MCB or fuse for short-circuit interruption. The 8/20 µs impulse withstand of 200 A means it survives common lightning-induced surges without nuisance tripping; that's a real advantage in a nacelle or outdoor panel where surge events are routine.
Installation and wiring notes
Mounts via clip-on to a standard DIN rail. Wire stripping length is 14 mm. Neutral is on the left. The 4-module width (36 mm,) takes four 9 mm pitches on the rail.