The Siemens 5SV3347-6KK12 is a SENTRON 5SV3-series residual current circuit breaker (RCCB) — 4-pole, Type A, rated 80 A at 40 °C and 400 V AC.
The 80 A rating is at 40 °C ambient; above that, the device derates linearly — 77.57 A at 45 °C, 74.59 A at 50 °C, 70.22 A at 55 °C, 64.47 A at 60 °C, 57.35 A at 65 °C, and 48.84 A at 70 °C. If your panel runs warm (say, 50 °C inside the enclosure), the continuous load must stay under 74.59 A. The conductor range accepts solid or stranded from 0.75 mm² up to 35 mm² — covers most branch-circuit wiring from 1.5 mm² through 10 mm² comfortably. The 70 mm depth and 72 mm width (4 width units on DIN rail) mean it occupies four 18 mm module spaces; verify your rail has room before pulling the old unit.