Siemens 5SY4280-6 — 2-pole B-curve MCB for general distribution
It breaks fault currents up to 10 kA per EN 60898 at 400 V AC, 50/60 Hz — enough for most commercial and light industrial sub-distribution boards.
Thermal derating and ambient limits
Rated current drops with panel ambient temperature: 80 A at 35 °C, 74.16 A at 45 °C, 72.16 A at 50 °C, 70 A at 55 °C, and 67.84 A at 60 °C. If the enclosure runs hot — say next to a transformer or in a sealed cabinet — size the upstream protective device for the derated figure, not the 35 °C nameplate.
IP20 with connected conductors — no washdown rating, so keep it inside the enclosure.