The Siemens 5SM9322-6KN is a SENTRON RC unit electronic, a 2-pole residual current device (RCD) with a 40 A rated current and a 30 mA tripping threshold, Type A, for 230 V AC at 50 Hz. The instantaneous design means it trips with no intentional delay, so it's the right choice where fast disconnection is needed — typically on final circuits supplying socket outlets or handheld equipment.
The 2-pole form factor snaps onto a DIN rail inside the distribution board. Rated 40 A continuous, it feeds directly from a 40 A upstream MCB or as a standalone RCD for a subcircuit. The 30 mA trip level provides additional fire and personnel protection on socket-outlet circuits. Power dissipation is 0.8 W per pole in the hot operating state, so thermal buildup in a crowded enclosure stays manageable — no forced cooling needed for normal residential or light commercial panels.
The 40 A rating means this RC unit can carry a 40 A load continuously without overheating, matching a 40 A MCB upstream for full selectivity. Type A detection handles the pulsed DC from rectified circuits (computers, LED drivers, variable-speed drives), so it's not limited to purely sinusoidal faults. The 230 V AC, 50 Hz supply voltage is the standard single-phase European residential and light commercial mains.