What this MCB is and what it does
The Siemens SENTRON 5SY4320-6CC is a 3-pole miniature circuit breaker (MCB) with B-curve tripping characteristic, rated 20 A at 35 °C and breaking 10 kA per EN 60898 or 5 kA per UL 1077 / CSA C22.2 No. 235. B-curve means it trips between 3 and 5 times rated current — suited for resistive and general-purpose loads where inrush is modest, not motor-heavy circuits. The 10 kA SCCR at 400 V AC means it safely interrupts fault currents up to that level without cascading upstream, which is the standard requirement for most distribution panels in commercial and light industrial builds.
Panel fit and mounting
Snaps onto DIN rail via the quick assembly system; mounting position is any, so it works in horizontal or vertical busbar layouts. Occupies 3 modular width units (54 mm wide). Depth is 76 mm, installation depth 70 mm — standard for a 3-pole MCB in a distribution board. IP20 with connected conductors; finger-safe terminals top and bottom (touch protection per the spec). Accepts ambient from -40 °C to 75 °C, with derating above 35 °C: 18.8 A at 40 °C, 18.18 A at 45 °C, 17.52 A at 50 °C, 16.84 A at 55 °C.