The Siemens 5SL4210-8 is a 2-pole SENTRON miniature circuit breaker with a D tripping characteristic, rated at 10 A and 10 kA breaking capacity per EN 60898 and IEC 60947-2 at 400 V AC. The D-curve is built for loads with high inrush — motor starters, small transformers, or capacitor banks — where the magnetic trip holds off until roughly 10–20× rated current, avoiding nuisance trips on startup.
Ratings and thermal derating
At 30 °C ambient the breaker carries the full 10 A; at 40 °C it derates to 9.24 A, at 45 °C to 8.8 A, and at 55 °C to 7.96 A. The DC-side rating is 72 V maximum, so this is an AC-primary breaker; for a DC sub-circuit at higher voltage you need a different pole configuration. IP20 with connected conductors — finger-safe once installed, but not protected against dripping water.
Sealable — you can lock the toggle position to prevent unauthorised switching.