What this breaker is and what it protects
The Siemens 5SL4403-6 is a 4-pole miniature circuit breaker from the SENTRON family, rated 3 A with a B tripping characteristic. That B-curve means it trips between 3 and 5 times rated current — so 9 A to 15 A — making it the right choice for resistive or general-purpose loads where you want fast clearing on short circuits but tolerance for small inrush spikes like lighting or control transformers. Breaking capacity is 10 kA per both EN 60898 and IEC 60947-2 at 400 V AC, so it can safely interrupt fault currents up to 10 000 A without welding contacts or cascading failure upstream. That rating is the same under both standards, which simplifies specification across residential and industrial panel builds. Rated for 400 V AC multi-phase operation, maximum 440 V AC, at 50/60 Hz.
Depth is 76 mm, installation depth 70 mm, so it sits flush with other SENTRON 5SL series breakers in a row. Halogen-free and silicon-free construction — no corrosive off-gassing if the breaker arcs internally, which matters in sealed or sensitive electronics panels.