What this MCB is and where it fits
The Siemens 5SY5425-7 is a 4-pole miniature circuit breaker from the SENTRON family, designed for universal current operation (AC/DC) and rated at 400 V AC (multi- and single-phase) with a C tripping characteristic. It carries a 10 kA breaking capacity per IEC/EN 60898-2 and a 15 kA rating per IEC 60947-2 at DC, making it suitable for branch-circuit protection in distribution boards and control panels where moderate inrush currents — typical of motor starters, contactor coils, and lighting banks — are expected. The C-curve trips between 5 and 10 times rated current, so it holds through the short-duration surge of a motor start but clears a hard fault fast.
Key ratings and what they mean for fit
Rated for 400 V AC (multi-phase) and 440 V AC (single-phase), with a DC operating voltage up to 1,000 V. The 10 kA breaking capacity at AC per EN 60898-2 means it can safely interrupt a fault current up to that level without welding contacts or cascading upstream; the 15 kA DC rating per IEC 60947-2 gives additional headroom for DC bus protection in industrial supplies. The C characteristic is the standard choice for general-purpose loads — it avoids nuisance trips on transformer inrush or motor start while still protecting the cable. The 4-pole design (4P) switches all phases; neutral is not switched, which is the common arrangement for TN and TT systems where the neutral is bonded at the source.
Mounting and integration into a panel
Occupies 4 modular width units (72 mm wide) on a DIN rail, with a quick-assembly fastening system that snaps onto the rail without tools. Mounting position is any orientation, which simplifies layout in crowded enclosures. Depth is 76 mm (installation depth 70 mm), so it fits standard 100 mm deep distribution boards with room for wiring. The combined terminal top and bottom accept conductors up to the rated cross-section; the terminals are sealable for metering applications where tamper evidence is required. IP20 with connected conductors — suitable for dry indoor panels; not rated for washdown or outdoor exposure.
Environmental and compliance
Rated for ambient temperatures from -40 °C to 75 °C, with a derating curve above 55 °C (95% humidity up to 55 °C, 55% up to 70 °C, 35% up to 75 °C). Halogen-free and silicon-free construction, which matters for installations in clean rooms, semiconductor fabs, or areas with sensitive electronics where outgassing can cause contact corrosion. Vibration resistance per IEC 60068-2-6: ±1 mm at 5 to 25 Hz, 50 m/s² at 25 to 150 Hz — sufficient for mounting on machinery or in mobile equipment. Pollution degree 2 and overvoltage category II, standard for fixed-installation distribution.