The Siemens 5SU1656-1KK20 is a 2-pole (1P+N) RCBO from the SENTRON 5SU1 series, combining overcurrent and residual current protection in a single 36 mm wide module. Rated 20 A at 30 °C with a C tripping characteristic, it breaks fault currents up to 6 kA per EN 60898 at 230/240 V AC. The residual current element is type AC, covering sinusoidal AC fault currents. This is the instantaneous (non-time-delayed) version, so it trips without intentional delay on earth faults — suitable for circuits where selectivity with upstream RCDs is not required.
Thermal derating and mounting
Rated current drops with ambient temperature inside the panel: 18.8 A at 40 °C, 18.2 A at 45 °C, 17.4 A at 50 °C, 16.2 A at 55 °C and 60 °C, 15.4 A at 65 °C, and 14.6 A at 70 °C. The device can be mounted in any position, with an installation depth of 70 mm. Supply can enter from the top or bottom — no mandatory orientation. It occupies 2 width units (36 mm) on a DIN rail. IP20 rating applies only when installed in a distribution board with connected conductors; the enclosure provides the final seal.