What it is and what it does
The Siemens 5SL4205-7 is a SENTRON miniature circuit breaker — 2-pole, C-curve, rated 0.5 A at 400 V AC, with a 10 kA breaking capacity per both IEC 60898 and IEC 60947-2. That 10 kA rating means it can safely interrupt a fault current up to 10,000 A without welding its contacts or cascading the fault upstream — critical for panel coordination in residential and light commercial infrastructure.
Ratings that matter for fit
The C-curve (tripping characteristic class C) means the magnetic trip fires at 5 to 10 times rated current — so for a 0.5 A breaker, instantaneous trip occurs between 2.5 A and 5 A. That suits it for moderate inrush loads like small transformers or lighting ballasts, not motor starts. At 30 °C it carries the full 0.5 A; at 40 °C it derates to 0.47 A, at 45 °C to 0.46 A, and at 55 °C to 0.43 A — so if the panel runs hot, factor that derating into the load calculation. The 2-pole design (2 modular width units, 36 mm wide per DIN 43880) snaps onto a standard DIN rail. Mounting position is any — no orientation restrictions. Depth is 76 mm, installation depth 70 mm. IP20 with connected conductors, overvoltage category III, pollution degree 2 — standard for enclosed distribution boards.