What this MCB is and where it goes
The Siemens 5SY4580-7 is a C-curve miniature circuit breaker from the SENTRON family, rated 80 A at 35 °C ambient. Two poles in a 1P+N design means it switches and protects the line conductor while switching the neutral — standard for single-phase final circuits in European panel builds. The 10 kA breaking capacity per IEC/EN 60898-1 covers most commercial and light industrial fault levels; the dual rating also meets IEC/EN 60947-2 for industrial applications where the fault current might push higher. Mounts on DIN rail via the quick-assembly system, any position, occupying 2 modular width units (36 mm). The IP20 rating applies with conductors connected — standard for enclosed distribution boards. Depth of 76 mm and installation depth of 70 mm mean it sits flush in a standard 125 mm deep enclosure without crowding the gland plate.
Temperature derating — real-world current capacity
At 35 °C this MCB carries its full 80 A. At 40 °C it derates to 76.16 A, at 45 °C to 74.16 A, at 50 °C to 72.16 A, at 55 °C to 70 A, and at 60 °C to 67.84 A. If your panel runs warm — and most enclosed distribution boards do — the 40 °C figure is the one to spec against, not the 35 °C headline. The C-curve characteristic trips between 5× and 10× In, so it handles motor inrush and transformer magnetizing current without nuisance trips on circuits that aren't purely resistive.
Compliance and approvals
Certified to IEC/EN 60898-1 and IEC/EN 60947-2. Overvoltage category III, pollution degree 3 — suitable for fixed installations inside a distribution board. Halogen-free and silicon-free construction. Sealable for lockout/tagout. Touch protection is built in. The combined terminals top and bottom accept the same conductor range, so wiring direction doesn't matter — speeds up panel assembly.