The Siemens 5SU1356-1DA20 is an FI/LS combination unit — an RCD and MCB in one DIN-rail module — rated 20A C-curve with 30mA residual current sensitivity and 6kA breaking capacity. The Type AC designation means it detects sinusoidal AC residual currents only, which covers standard domestic and light commercial circuits without electronic loads that generate pulsed DC fault currents.
The 70 mm depth (D=70MM) and pigtail connection make it a direct swap for existing Siemens FI/LS units in standard distribution boards. The 1+N-pole configuration protects one live conductor and switches the neutral; the pigtail simplifies wiring in pre-assembled panel layouts where busbar access is tight.