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. It's rated 20 A with a Type C tripping characteristic and 30 mA residual current sensitivity, breaking capacity 6 kA per EN 60898. This is the go-to for final subcircuits in residential and light commercial distribution boards where you need both MCB and RCD in one DIN-rail slot.
What the ratings mean for your panel
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. The Type C curve (5-10x In magnetic trip) handles moderate inrush from small motors, transformers, or fluorescent lighting without nuisance trips. The 30 mA residual current rating is the standard for personal protection against direct contact in IEC 60364 installations. The AC-type RCD detects sinusoidal AC fault currents only — fine for general socket-outlet circuits, but not for appliances with rectified or pulsed DC fault profiles (those need Type A or F). The 6 kA breaking capacity (EN 60898) is adequate for domestic and light commercial panels where the prospective short-circuit current at the board doesn't exceed that level.
DIN-rail footprint and integration
Occupies 2 modular width units (36 mm) on a standard DIN rail. 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.