Siemens 5SY7220-8CC — 2-pole D-curve MCB for industrial branch circuits
The Siemens 5SY7220-8CC is a 2-pole miniature circuit breaker from the SENTRON 5SY7 series, rated 20 A at 400 V AC with a D tripping characteristic. The D-curve (10–20× In) is designed for loads with high inrush currents — motor starters, transformers, and discharge lighting — where a B or C curve would nuisance-trip on startup. The 25 kA breaking capacity per IEC 60947-2 (5 kA per UL 1077) means it can safely interrupt fault currents up to that level without upstream coordination issues in most industrial panelboards. It snaps onto a 36 mm wide (2 MW) DIN rail and accepts solid or stranded conductors from 0.75 to 35 mm² at the screw terminals.
D-curve and breaking capacity — what they mean for your panel
The D tripping characteristic (magnetic trip at 10–20× rated current) means this breaker holds through the short-duration inrush of a motor or transformer without opening, then clears a hard fault fast. The 25 kA IEC 60947-2 rating (5 kA UL 1077) gives you the SCCR headroom for most industrial distribution boards — if your available fault current exceeds 25 kA, you need a current-limiting upstream device. Overvoltage category III (pollution degree 2) suits fixed-installation panels. The breaker is touch-protected (IP20 with conductors connected) and rated for ambient temperatures from -25 to +55 °C.
Mounting and wiring — DIN-rail fit and terminal details
Snaps onto a 35 mm DIN rail via the quick-assembly system; mounting position is any orientation. The 2-pole unit occupies 36 mm (2 width units). Installation depth behind the panel is 70 mm; overall depth is 76 mm. Screw terminals accept solid or stranded copper from 0.75 to 35 mm²; tightening torque is 2.5 to 3.5 N·m. Combined terminals (top and bottom) allow busbar or ring-lug connections. The breaker is sealable for lockout/tagout. Halogen-free and silicon-free construction suits clean-room or sensitive environments.