What this MCB is and what the ratings mean
The Siemens 5SY4408-8CC is a 4-pole miniature circuit breaker from the SENTRON 5SY series, designed for DIN-rail mounting in distribution boards and control panels. Its D tripping characteristic means it tolerates the high inrush currents typical of motor loads, transformers, and discharge lighting — the magnetic trip threshold sits at 10–20× rated current, so nuisance tripping on startup is avoided. Rated 8 A at AC and 10 kA breaking capacity per EN 60898, it handles fault currents up to that level without cascading upstream. The 4-pole construction switches all three phases plus neutral; note the neutral is not switched separately — the breaker opens all poles together.
Temperature derating and installation notes
Rated current is temperature-sensitive: at 40 °C ambient the continuous rating drops to 7.52 A, at 50 °C to 7.01 A, and at 55 °C to 6.74 A. If the panel runs hot, factor the derating into the load schedule. The breaker occupies 4 modular width units on a DIN rail, with a quick-assembly fastening system and any mounting position. Installation depth is 70 mm. IP20 with connected conductors — standard for enclosed distribution boards; not rated for washdown. Pollution degree 3 suits industrial environments with conductive dust or condensation.