Breaking capacity and trip curve
The 5SY4420-6 carries a dual breaking-capacity rating: 10 kA per EN 60898 for general-distribution duty, and 20 kA per IEC 60947-2 for industrial panel applications where the prospective fault current is higher. The B-curve characteristic (tripping between 3 and 5× rated current) is the standard choice for resistive and general-purpose loads — lighting, small transformers, control circuits — where inrush is low and fast magnetic trip on short-circuit is wanted.
Temperature derating in the panel
Rated current is 20 A at 35 °C ambient. The SENTRON derating table is explicit: 19.04 A at 40 °C, 18.54 A at 45 °C, 18.04 A at 50 °C, 17.5 A at 55 °C, and 16.96 A at 60 °C. If the breaker sits in a crowded enclosure with multiple heat sources, use the 40 °C or 50 °C column for the continuous-load budget — the thermal-magnetic element responds to internal temperature, not just the nameplate value.
DIN-rail fit and wiring
Four modular-width units (72 mm wide) on a standard 35 mm DIN rail. Depth is 76 mm, height 90 mm. The quick-assembly system snaps on without tools; mounting position is any orientation. Combined terminals top and bottom accept the supply from either end — no need to flip the breaker for top-feed vs bottom-feed. IP20 with conductors connected; overvoltage category III, pollution degree 3.