The Siemens 5SY8406-7 is a SENTRON 4-pole miniature circuit breaker rated 6 A with a C-curve trip characteristic, designed for mechanical engineering and industrial panel applications. Its 50 kA breaking capacity at 400 V AC (per IEC 60947-2) means it can safely interrupt high fault currents without cascading upstream — a key spec for high-available-fault panels where a standard 10 kA MCB would weld closed.
Depth is 76 mm, installation depth 70 mm — that 6 mm difference is the front toggle overhang, so plan gland-plate clearance for the full 76 mm. Mounting position any, which helps in tight enclosures where you're stacking breakers sideways.
Thermal derating and environmental limits
Rated 6 A at 45 °C ambient; at 50 °C it derates to 5.85 A, and at 55 °C to 5.69 A. That's about 2.5% drop per 5 °C above 45 °C — plan your panel internal temperature if you're loading all four poles near the limit. Ambient range is -40 °C to 75 °C, with humidity limits: 95% RH up to 55 °C, tapering to 35% RH at 75 °C.