What it is and what it does
The Siemens 5SU1354-1KK16 is a SENTRON RCBO — a combined residual-current circuit breaker with overcurrent protection, in a 1P+N, 2-pole format. It protects a single-phase line against earth faults and overloads/short-circuits in one 36 mm-wide module, saving a DIN rail position compared to separate RCCB + MCB. Rated 16 A at 30 °C with a C tripping characteristic (magnetic release at 5–10× In), it handles general-purpose loads like lighting circuits, socket outlets, and small appliances where moderate inrush is expected. The 10 kA breaking capacity per EN 60898 covers most domestic and light commercial distribution boards; the 20 kA rating per IEC 60947-2 gives headroom for industrial panel coordination where higher fault currents are possible.
Temperature derating — the real current rating on your panel
The 16 A rating holds only at 30 °C ambient inside the distribution board. At 40 °C it's 15.2 A; at 50 °C it drops to 14.4 A; at 60 °C it's 13.6 A; at 70 °C it's 12.32 A. If your panel runs hot — say, a packed enclosure near a furnace line or in a non-ventilated cabinet — the 5SU1354-1KK16 must be derated accordingly. The full curve is on the nameplate; don't spec it at 16 A unless you can guarantee the 30 °C ambient.
Mounting and integration
Two modular width units (36 mm) snap onto a DIN rail. Depth is 77 mm, height 90 mm, installation depth 70 mm — fits standard distribution boards and sub-distribution panels. Supply can enter from top or bottom; mounting position is any orientation. IP20 with connected conductors, so it's for enclosed use only — not for washdown or outdoor without a weatherproof enclosure. Halogen-free and silicon-free construction matters for panels in clean rooms, semiconductor fabs, or any environment where outgassing from a fault could contaminate optics or sensitive electronics. Degree of pollution 2 and overvoltage category III are standard for fixed-installation distribution boards.