The Siemens SENTRON 5SJ4308-8HG41 is a 3-pole miniature circuit breaker (MCB) with a D tripping characteristic, rated 8 A at both 30 °C and 40 °C ambient.
Thermal derating and enclosure fit
Rated current holds at 8 A up to 40 °C, then steps down: 7.8 A at 45 °C, 7.6 A at 50 °C, 7.4 A at 55 °C, and 7.2 A at 60 °C (–). The 70 mm depth and 54 mm width match the standard SENTRON 5SJ4 footprint — no surprises when swapping into an existing DIN-rail layout. Degree of pollution 3 and overvoltage category 3 suit industrial control panels, not just residential.