20 A C-curve MCB for 400 V AC panels — 25 kA IEC breaking capacity
The Siemens 5SY7420-7CC is a 4-pole miniature circuit breaker from the SENTRON 5SY7CC series, rated 20 A at 400 V AC with a C tripping characteristic. Its 25 kA breaking capacity per IEC 60947-2 handles high-fault scenarios common in industrial distribution boards — enough to clear a bolted fault downstream of a 630 kVA transformer without cascading upstream. For UL 1077 / CSA C22.2 No.235 installations the interrupting rating is 5 kA, so confirm the available fault current if the panel is destined for a North American job site. Four poles (4P, 4 MW wide) with no switched neutral — the neutral conductor is not broken, so this breaker suits three-phase loads where a solid neutral is required. Mounts in any position on the DIN rail via the quick-assembly system. The housing is halogen-free and silicon-free, which matters for panels going into clean-room or food-bev environments where outgassing contaminates optics or product.
Terminal and wiring detail
Screw-type terminals accept solid or stranded conductors from 0.75 mm² up to 35 mm². Tightening torque range is 2.5 to 3.5 N·m — a standard Pozidriv or hex driver, no special tooling. Combined terminals at both top and bottom mean you can feed-through or loop out without separate ring lugs. Strip length isn't stated in the spec; typical practice for this terminal class is 12-14 mm, but verify against the actual lug pocket on first sample. Depth is 76 mm, installation depth 70 mm. Width 72 mm (4 MW), height 90 mm. The sealable cover option (yes) lets the panel builder lock out tampering after commissioning — useful for rental or shared-access enclosures.
Ambient limits and storage
Operating ambient -25 to +55 °C. Storage range -40 to +75 °C — that wider band governs shipping and warehousing, not running. Humidity influence: max 95% RH at 55 °C, derating to 55% at 70 °C and 35% at 75 °C. Overvoltage category III, pollution degree not explicitly listed but typical for this class is PD2.