The Siemens 5SY7425-8CC is a SENTRON miniature circuit breaker (MCB) with a D tripping characteristic, 4 poles, rated 25 A at 400 V AC. It carries a 15 kA breaking capacity per IEC 60947-2 — that's the fault-clearing rating that governs its use in industrial distribution panels where high inrush loads (transformers, motor starters) are downstream. The D curve means magnetic trip occurs at 10–20× rated current, sized to ride through the startup surge of inductive loads without nuisance tripping. Physically it occupies 4 modular width units (72 mm wide) on a DIN rail, with a depth of 76 mm and height of 90 mm. The quick-assembly fastening system and any-position mounting simplify panel layout — no orientation restrictions when fitting into a crowded enclosure.
Breaking capacity and compliance
The IEC 60947-2 rated breaking capacity of 25 kA at 400 V AC is the headline figure for industrial installations. For UL 1077 / CSA C22.2 No. 235 supplementary protection applications, the rating is 5 kA — a different standard, not a downgrade; it reflects the UL test protocol for branch-circuit protection. The overvoltage category is III (distribution-level) and pollution degree 3 (conductive pollution typical in industrial environments). Mechanical service life 10,000 operating cycles typical. Power loss per pole 2.1 W at rated current in hot state.
Environmental and installation
Ambient temperature range -40 °C to 75 °C. Humidity derating: max 95% RH at 55 °C, 35% at 75 °C. IP20 with connected conductors. Housing halogen-free and silicon-free. Sealable for tamper-evident applications. Combined terminals at top and bottom.