What this MCB does and where it fits
The Siemens SENTRON 5SL4250-8CC is a 2-pole miniature circuit breaker with a D tripping characteristic, rated 50 A at 400 V AC and a breaking capacity of 10 kA per EN 60898. The D-curve means it's designed for loads with high inrush currents — typically motor circuits, transformers, or discharge lighting — where the magnetic trip threshold (10–20× In) avoids nuisance tripping on startup. Rated current derates with ambient temperature: 46.19 A at 40 °C, 44.17 A at 45 °C, 42.05 A at 50 °C, and 39.81 A at 55 °C. If the panel ambient runs above 30 °C, size the upstream protection for the derated value, not the 50 A nameplate. Occupies 2 modular width units (36 mm) on a DIN rail. Depth is 76 mm, installation depth 70 mm. Mounting position is unrestricted — can be oriented vertically, horizontally, or flat against the rail.
Lifecycle and sourcing status
No official successor has been published. The part is a standard catalog item in the SENTRON portfolio, so lead times are typically consistent with Siemens' production schedules for this class.
Compliance and environmental ratings
Rated for overvoltage category III, pollution degree 2. The housing is sealable, halogen-free, and silicon-free — relevant for clean-room or sensitive electronics environments where outgassing must be minimized. Touch protection is integrated (finger-safe terminals). IP20 with connected conductors — suitable for enclosed distribution boards, not for wet or washdown locations. Vibration resistance tested to IEC 60068-2-6: 50 m/s² at 25 to 150 Hz, which covers typical industrial panel vibration from nearby drives or contactors.
Electrical ratings and coordination notes
Maximum operating voltage on multi-phase AC circuits is 440 V. Single-phase supply rated at 400 V AC. For DC circuits, the maximum rated voltage is 72 V — this is not a general-purpose DC breaker for higher-voltage battery banks or solar strings. The neutral conductor is not switched (2-pole design switches both phase conductors, no integral neutral pole). Suitable for 2-phase or single-phase 2-wire applications where both lines are protected. Suitability listed for residential buildings and infrastructure — standard distribution board installation. Not specifically rated for motor-starting duty beyond the D-curve's inrush tolerance; verify coordination with downstream contactors if used in a motor branch circuit.