The Siemens 5SU1354-3KK25 is a 2-pole (1P+N) RCBO from the SENTRON 5SU1 series, combining overcurrent protection and residual current detection in a single 36 mm wide unit. Breaking capacity is 10 kA per EN 60898 at 230/240 V AC, overvoltage category III, pollution degree 2. Energy limiting class 3 means it limits let-through energy well enough for most downstream equipment protection.
Thermal derating — what the numbers mean
The 25 A rating holds only at 30 °C ambient. At 40 °C it's 23.5 A, at 50 °C it's 21.75 A, and at 60 °C it drops to 20.25 A. By 70 °C you're down to 18.25 A.
Mounting position is any — no restriction on upright or sideways. IP20 with conductors connected and distribution board installed. Halogen-free and silicon-free construction for environments sensitive to outgassing.