The Siemens SENTRON 5SJ4125-7HG42 is a 1-pole miniature circuit breaker with C-curve tripping characteristic, rated 25 A at 30 °C and 40 °C.
Ratings and fit
Full rated current holds at 30 °C and 40 °C (25 A), then derates linearly to 22 A at 60 °C — useful if the breaker sits in a warm cabinet near drives or transformers. The 70 mm installation depth matches standard SENTRON 5SJ4 enclosures and most DIN-rail distribution boards; no extra clearance needed at the back. Overvoltage category 3 and pollution degree 3 mean it's rated for fixed installations in industrial environments, not just clean residential panels. IP20 with connected conductors, IP40 in the handle area — fine for enclosed panels; not for washdown zones without a separate enclosure. Vibration resistance to 50 m/s² at 25–150 Hz and 60 m/s² at 35 Hz means it holds up on machine-mounted subpanels near rotating equipment.