The Siemens 5SN6125-8CP is a 1-pole SENTRON miniature circuit breaker (MCB) from the 5SN series, rated for 400 V AC supply voltage at 50 Hz and up to 72 V DC. It occupies one modular width unit (18 mm wide).
The 6 kA rating under EN 60898 covers standard residential and light commercial installations. Multi-phase operation is rated at 440 V AC maximum, single-phase at 440 V AC as well, so it handles line-to-line faults in a 400 V three-phase system. Power loss per pole is 2.1 W in hot operating state at rated current.
Accepts solid conductors up to 35 mm².