The Siemens 5SU9356-1CR20 is a SENTRON RCD-operated circuit breaker (RCBO) combining overcurrent and residual current protection in a single 2-module-width package.
The 20 A rating is at 30 °C ambient; at 40 °C it derates to 18.8 A, at 45 °C to 18.2 A, at 50 °C to 17.4 A, and at 55 °C to 16.2 A. If your distribution board runs warm — say, tightly packed with other breakers — size the circuit load against the derated figure, not the nominal 20 A.
DIN-rail footprint and integration
Depth is 77 mm, height 90 mm, installation depth 70 mm. Mounting position any, supply feed from top or bottom. IP20 with conductors connected — meaning it's protected against finger contact only when wired inside a closed distribution board. Pollution degree 2, overvoltage category III, suitable for fixed installations downstream of the main panel.