The Siemens SENTRON 5SU9106-1KK20 is a combined RCD and MCB — an RCBO — in a single 18 mm wide module. It protects a 1P+N circuit (one protected pole, switched neutral) against overload, short-circuit, and earth leakage, all in one unit. The C tripping characteristic means it handles moderate inrush from motorized or capacitive loads without nuisance tripping; the 20 A rating at 30 °C derates to 18.8 A at 40 °C and 16.2 A at 55 °C, so check the ambient inside your enclosure before committing the BOM line. The instantaneous design (no intentional delay) clears fast on high faults, which helps with energy-limiting class 3 coordination downstream.
Snaps onto standard DIN rail. At 18 mm wide (1 width unit), it occupies a single module position. Installation depth is 70 mm; the overall depth including the front is 77 mm. Supply can enter from either top or bottom, which simplifies busbar routing in a crowded distribution board. IP20 protection applies once the distribution board is installed with conductors connected — the front face is touch-protected per the product feature listing.