The Siemens 5SU1354-6KK20 is a SENTRON RCBO — a combined residual-current circuit breaker and overcurrent protection device in a single 2-module-wide housing. It protects a single-phase final subcircuit: one pole switched, neutral switched but not protected. The B-curve tripping characteristic means it clears short-circuit faults between 3 and 5 times the rated current (60–100 A instantaneous), which suits resistive and general-purpose loads where inrush is modest — lighting, small heaters, control transformers, socket outlets in residential or light commercial distribution boards.
Ratings and what they mean for fit
Rated 20 A at 30 °C ambient, this RCBO derates linearly as the panel temperature climbs: 18.8 A at 40 °C, 17.4 A at 50 °C, 15.4 A at 65 °C, and 14.6 A at 70 °C. If your distribution board sits in a hot mechanical room or next to a furnace, the 30 °C figure is not the one you spec against — use the 50 °C or 65 °C column. The breaking capacity is 10 kA per EN 60898 (the standard for household-type MCBs) and 20 kA per IEC 60947-2 (the industrial standard) — so it handles fault currents up to 20 kA in an industrial panel where the prospective short-circuit current is higher. Overvoltage category III and pollution degree 2 are standard for fixed-installation distribution boards. Operating temperature range spans -40 °C to 75 °C, which covers unheated outdoor enclosures in cold climates and hot roof spaces. The unit is halogen-free and silicon-free — relevant for semiconductor fabs, clean rooms, or any environment where outgassing from a fault event must not corrode nearby contacts or optics.
Mounting and panel integration
Two modular-width units (36 mm) snap onto standard DIN rail. Depth is 77 mm, installation depth 70 mm — check your enclosure depth before committing the BOM; a shallow 80 mm enclosure leaves only 3 mm clearance behind the device. Supply can enter from top or bottom, which simplifies busbar routing in a crowded board. Rated IP20 with conductors connected and distribution board installed — this is a panel-internal device, not for standalone outdoor use without an enclosure.