Siemens 5SY5150-7 — C-curve MCB for universal-current branch circuits
It breaks 10 kA per IEC/EN 60898-2 at 400 V AC and 15 kA per IEC 60947-2 at 250 V DC — the higher DC rating matters when clearing faults on control-power or PV-string circuits where DC arc extinction is harder. Rated operating voltage is 400 V AC single-phase (440 V max) and 220 V DC (250 V max).
Depth is 76 mm (70 mm installation depth). Mount in any position — no derating for orientation. The IP20 rating applies with connected conductors; the sealable option (padlockable toggle) allows lockout/tagout without an external lockout hasp. Combined top and bottom terminals simplify daisy-chaining busbars or looping feed-through. Halogen-free and silicon-free construction avoids outgassing concerns in sealed enclosures or clean-room panels.
The 10 kA rating at 400 V AC (IEC/EN 60898-2) covers most commercial and light-industrial service-entrance fault levels. The 15 kA DC rating per IEC 60947-2 applies at 250 V DC — useful for DC distribution or battery-backed control circuits where the higher interrupting rating avoids cascading failure. Energy limitation class 3 means it lets through less let-through energy (I²t) than class 1 or 2 breakers, improving downstream device protection. Vibration resistance per IEC 60068-2-6 (±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz) covers most machine-mounted and conveyor-line applications.
Ambient derating and operating limits
Humidity derating applies above 55 °C: max 95% RH at 55 °C, dropping to 55% at 70 °C and 35% at 75 °C. In a hot panel near drives or transformers, expect the breaker to carry full rated current only up to 55 °C; above that, the thermal trip element shifts — account for derating in the branch-circuit ampacity calculation.