What this 4-pole C-curve breaker is for
The Siemens 5SY4625-7CV is a 4-pole miniature circuit breaker with a C tripping characteristic, rated 25 A at 35 °C and 440 V AC, with a 15 kA breaking capacity per IEC 60947-2. The C-curve (5–10× In) makes it the standard choice for moderate inrush loads — motor starters, small transformers, banks of LED drivers — where a B-curve would nuisance-trip on startup but a D-curve would delay too long for branch-circuit protection. The 4-pole format (3 phases + switched neutral) suits three-phase distribution panels where the neutral needs to be switched with the phases, common in European and IEC-style industrial switchgear.
Ratings that govern the fit
The headline 25 A rating holds at 35 °C ambient. Above that, the breaker derates linearly: 23.18 A at 40 °C, 22.2 A at 45 °C, 21.2 A at 50 °C, and 20.1 A at 55 °C. If your panel runs warm — and most closed industrial enclosures do — size the continuous load against the derated figure, not the 25 A nameplate. The 15 kA breaking capacity at 440 V AC means this breaker can safely interrupt a fault current up to that level without welding its contacts or cascading failure upstream; that's adequate for most secondary distribution boards fed by a transformer of 630 kVA or less. Vibration resistance per IEC 60068-2-6 (±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz) confirms it holds calibration under pump or compressor vibration — not just a static panel mount.
Panel integration and mounting
Mounts on a standard DIN rail via the quick assembly system — snaps on without tools, releases with a screwdriver push. The 4-module width (72 mm) matches the standard 18 mm per pole footprint. Installation depth is 70 mm, overall depth 76 mm. Any mounting position is allowed, which simplifies layout in crowded enclosures. Combined terminals top and bottom accept copper conductors; the sealable cover option (yes) lets the panel builder lock out unauthorized switching after commissioning. IP20 with conductors connected — protected against finger contact, not against washdown, so keep it inside a sealed enclosure in wet environments.
Environmental and compliance notes
Halogen-free and silicon-free construction — relevant for clean-room or semiconductor-adjacent installs where outgassing contaminates optics or process gases. Ambient temperature range spans -40 °C to 75 °C, with humidity limits: max 95% RH up to 55 °C, derating to 35% RH at 75 °C. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive due to condensation) means it's rated for industrial environments where the panel isn't climate-controlled. Overvoltage category III applies — suitable for fixed installations downstream of the main distribution board. The standard cited is IEC / EN 60947-2, the harmonized European standard for low-voltage switchgear and controlgear circuit breakers.