What it is and what it does
The Siemens SENTRON 5SL3125-6 is a 1-pole miniature circuit breaker rated 25 A with a B tripping characteristic. It breaks fault currents up to 4.5 kA per EN 60898 and 5 kA per IEC 60947-2, which covers the majority of residential and light-commercial distribution boards. The B-curve means it trips between 3 and 5 times rated current — fast enough for cable protection but tolerant of moderate inrush from lighting or small transformers.
Fit and form factor
Occupies 1 modular width (18 mm) on a DIN rail, with a depth of 76 mm and an installation depth of 70 mm. Mounting position is unrestricted, and the IP20 rating (with connected conductors) is standard for enclosed distribution boards. The housing is halogen-free and silicon-free, which matters for panels in clean-room or corrosive environments.