What this MCB is and where it fits
The Siemens 5SL3225-6 is a 2-pole miniature circuit breaker from the SENTRON 5SL3 series, rated 25 A with a B tripping characteristic. It's built for residential and infrastructure panels — think lighting, socket circuits, and general-purpose branch protection in a DIN-rail enclosure. The 4.5 kA breaking capacity per EN 60898 (also rated per IEC 60947-2 at the same value) covers typical domestic and commercial fault levels. At 2 width units (36 mm wide, 90 mm tall, 76 mm deep), it occupies two standard module slots on the rail.
What the ratings mean for your panel
The B curve means the magnetic trip activates at 3 to 5 times rated current (75–125 A for this 25 A unit), so it's a good fit for resistive and general-purpose loads where inrush isn't severe — lighting, small transformers, control circuits. The 4.5 kA breaking capacity per EN 60898 tells you it can safely interrupt a fault up to that level without welding contacts or cascading upstream. Rated 400 V AC phase-to-phase, with a maximum of 440 V in multi-phase operation. The 2-pole configuration switches both live conductors but does not switch the neutral — verify your circuit's neutral switching requirement before specifying. Terminal torque spec is 2.5 to 3 N·m, and the screw terminals accept solid or stranded conductors from 0.75 to 25 mm². Mounting position is unrestricted, and the ambient operating range is -25 to +45 °C.