The Siemens 5SY5125-6 is a 1-pole SENTRON miniature circuit breaker with a B tripping characteristic, rated to break 10 kA per IEC/EN 60898-2 and 15 kA per IEC 60947-2 at DC. It handles 400 V AC (single or multi-phase) and up to 220 V DC, making it suitable for universal-current branch circuits in distribution boards.
In a panel with mixed loads, a B-curve MCB avoids nuisance tripping on modest surges while still clearing fast on a hard fault. If your fault-current study shows available short-circuit current above 10 kA at the panel, the 15 kA DC rating under IEC 60947-2 gives extra headroom for DC circuits — a useful margin for battery-backed or solar-combiner applications. The IP20 rating applies only with connected conductors — treat the busbar area as live when the cover is off.
Where it goes in the panel
Mounting position is unrestricted — horizontal, vertical, or flat — which helps when you're packing breakers into a tight gland plate layout. Combined terminals at both top and bottom accept copper conductors without separate busbar clamps.
Listed to IEC / EN 60898-2 for residential-style MCB duty and to UL 1077 for supplementary protection in North American panels. The halogen-free and silicon-free construction means no corrosive off-gassing during a fault — important for sealed enclosures housing sensitive electronics. Vibration resistance per IEC 60068-2-6 covers ±1 mm at 5–25 Hz and 50 m/s² at 25–150 Hz, so it holds up on a machine skid or near a reciprocating compressor.