What this MCB does on the line
The Siemens 5SY7420-8 is a 4-pole miniature circuit breaker from the SENTRON family, rated for 400 V AC and 60 V DC. Its D tripping characteristic means it handles inrush currents typical of motor loads, transformers, or welding equipment — the magnetic trip threshold is 10 to 20 times rated current, so nuisance tripping on startup is avoided. The breaker carries a 15 kA breaking capacity per EN 60898 and 25 kA per IEC 60947-2, giving headroom for high-fault installations. At 72 mm wide (4 modular units), it occupies standard DIN-rail space; the quick-assembly system and any mounting position simplify panel integration.
Breaking capacity and standards — what the ratings mean
The 15 kA rating under EN 60898 is the standard for residential and light commercial panels in IEC markets. The 25 kA rating under IEC 60947-2 covers industrial installations where fault currents are higher — that's the number a panel designer uses for SCCR coordination. For UL 1077 / CSA C22.2 No.235, the breaker is listed at 5 kA, which is typical for supplementary protection in North American control panels. The part also meets overvoltage category III and pollution degree 3, so it's suited for fixed installations in industrial environments.
Panel fit and environmental limits
The breaker mounts on a DIN rail via the quick-assembly system; the 72 mm width (4 MW) matches standard modular spacing. Depth is 76 mm, installation depth 70 mm. Ambient temperature range is -40 °C to 75 °C, with derating for humidity (95% at 55 °C, 55% at 70 °C, 35% at 75 °C). The IP20 rating with connected conductors means it's protected against finger contact but not washdown — suitable for enclosed panels. Vibration resistance per IEC 60068-2-6 covers ±1 mm at 5 to 25 Hz and 50 m/s² at 25 to 150 Hz, which is typical for industrial machinery.