The Siemens SENTRON 5SL3125-6MB is a 1-pole miniature circuit breaker with a B tripping characteristic, rated 25 A at 400 V AC. It breaks faults up to 4.5 kA per EN 60898, which covers residential and light commercial service entrance and subpanel protection where the prospective short-circuit current stays under that threshold.
What the ratings mean for fit
B-curve tripping (3–5× In) means this breaker holds through modest inrush — think lighting, resistive heaters, general-purpose outlets — but will nuisance-trip on motor-start surges. If the load has a motor or transformer inrush, step to a C-curve sibling. The 4.5 kA breaking capacity is the fault current it can safely interrupt; if your service panel's prospective short-circuit current exceeds that, you need a higher-rated breaker or a current-limiting upstream device. Rated 25 A continuous at 400 V AC. Also carries 250 V AC single-phase rating. The 440 V max multi-phase rating covers 3-phase line-to-line applications. At 50 Hz only.
Panel fit and wiring
Snaps onto standard DIN rail, 18 mm wide (1 width unit), 76 mm deep with 70 mm installation depth behind the panel. Accepts conductors from 0.75 mm² up to 25 mm² — solid or stranded. Mount in any position. IP20 with conductors connected, so it belongs inside a closed enclosure, not in a wet location. Sealable and touch-protected. Halogen-free and silicon-free construction matters for panels in clean rooms or environments where outgassing can't contaminate optics or electronics. No neutral switching function — this pole breaks the phase only.