What it is and what it does
The Siemens 5SL3225-6MB is a 2-pole miniature circuit breaker rated for 400 V AC with a 4.5 kA breaking capacity, B-curve trip characteristic, and 25 A rated current. It belongs to the Basic Devices family within the SENTRON series. The B-curve (3–5× In) means it trips fast on moderate overloads — typical for residential or light commercial lighting and socket circuits where inrush is low. The 4.5 kA breaking capacity at 400 V is sufficient for most final subcircuits in a TN or TT system; it safely interrupts a fault up to that level without upstream cascading.
Panel integration note
Snap-on DIN rail mount, 2-pole width (about 36 mm). Packaging dimensions 216 × 93 × 82 mm. The 25 A B-curve is a common choice for general-purpose final circuits; watch derating if ambient exceeds 40 °C or if multiple breakers are ganged without spacing.