The 5SY8504-8 is a Siemens SENTRON miniature circuit breaker (MCB) rated 4 A with a D tripping characteristic, 2-pole construction (1P+N), and a 50 kA breaking capacity per IEC 60947-2 at 400 V AC. At 45 °C ambient it still carries the full 4 A; derate to 3.88 A at 50 °C and 3.75 A at 55 °C. For DC circuits, rated breaking capacity drops to 15 kA at a maximum 72 V DC. The 2-pole format with switched neutral (1P+N) means the neutral pole opens and closes with the phase — useful where isolation on both conductors is required by local code or application.
The quick-assembly fastening system snaps onto the rail; mounting position is any orientation. IP20 with connected conductors, so it belongs inside an enclosure, not exposed to washdown. Sealable terminals support lockout/tagout procedures. Vibration resistance per IEC 60068-2-6: ±1 mm at 5 to 25 Hz, 50 m/s² at 25 to 150 Hz. Pollution degree 3, overvoltage category III — rated for fixed installations in industrial environments where conductive pollution is possible.
The product designation follows EN 61346-2 and IEC 81346-2 function code F (protective device). Suitability for operation listed as mechanical engineering/industry.