The Siemens 5SL4503-6 is a SENTRON miniature circuit breaker — 1P+N, B-curve trip at 3 A, 230 V AC, 50/60 Hz. It breaks 10 kA per EN 60898 and IEC 60947-2, so it clears faults up to that level without upstream cascading in a residential or light-commercial panel.
The B curve trips between 3 and 5 times rated current (9–15 A magnetic release), which suits resistive and general-purpose loads — lighting, socket circuits, small appliances — where inrush stays moderate. The 3 A rating at 30 °C derates to 2.84 A at 40 °C and 2.59 A at 55 °C; if the panel runs hot, size up one step. Two modular width units (36 mm wide, 76 mm deep, 70 mm installation depth) snap onto DIN rail in any mounting position. IP20 with conductors connected — enclosed in a distribution board, not exposed to washdown. Rated for overvoltage category III (fixed installation) and pollution degree 2.