The Siemens 5SL4150-8 is a 1-pole SENTRON miniature circuit breaker with a D tripping characteristic, rated 50 A at 30 °C and 400 V AC. Its 10 kA breaking capacity is certified per both EN 60898 and IEC 60947-2, so it clears faults up to that level without upstream cascading in residential or infrastructure panels. The D-curve means it tolerates the high inrush of motor or transformer loads — trips magnetically at 10–20× rated current, not the 5–10× of a C-curve. That's the spec that decides fit for inductive circuits.
Derating and thermal reality
The 50 A rating holds at 30 °C. At 40 °C it's 46.19 A; at 45 °C, 44 A; at 55 °C, 39.81 A. If your panel ambient runs hot — say 45 °C inside the enclosure — you're effectively carrying a 44 A breaker. That's the number to spec against for continuous load, not the 30 °C headline. The part is rated for ambient up to 55 °C with 95% humidity, and storage from -40 to 75 °C.
Panel fit and mounting
Occupies 1 modular width unit (18 mm) on a DIN rail. Depth is 76 mm, installation depth 70 mm. Mounting position is unrestricted — can go horizontal or vertical. IP20 with connected conductors, so it's protected against finger contact but not washdown; keep it inside a closed panel. Pollution degree 2, overvoltage category III. Halogen-free and silicon-free construction, sealable for tamper-evident applications.