What this RCBO covers
The Siemens 5SU9306-1DV20 is a combined residual current device and miniature circuit breaker (RCBO) in a single 1+N-pole module. It provides both overcurrent protection (C-curve, 20 A rated current) and residual current protection (Type AC, 30 mA sensitivity) in one DIN-rail unit, saving a module width compared to separate MCB+RCCD. The Type AC detection handles sinusoidal AC residual currents — the standard choice for general socket-outlet and lighting circuits without electronic loads.
For a project buyer planning a panel build, this part can be specified into the BOM with confidence that supply will be consistent through the commissioning window.
The 70 mm depth (D=70mm) is standard for Siemens 5SU9 RCBOs — verify enclosure depth clearance if retrofitting into a shallow consumer unit originally designed for 60 mm deep devices. The 1+N-pole configuration switches the line conductor and disconnects the neutral; the neutral pole is not switched but is opened by the residual current mechanism. Wire the supply neutral to the N terminal on the device, not the busbar, for the RCD function to operate.