What it is and what it does
The Siemens 5SU9356-8CN50 is a 1+N RCBO (residual current circuit breaker with overcurrent protection) rated 50 A, 6 kA breaking capacity, D characteristic, Type A. The D curve means it tolerates high inrush currents — common on motor or transformer loads — without nuisance tripping. Type A residual protection catches pulsating DC fault currents (typical from rectified loads) as well as sinusoidal AC. The 6 kA short-circuit capacity is sized for final subcircuits in residential or light commercial distribution boards where the prospective fault current stays under that level.
Where it goes
Snap-on DIN-rail mount for standard 18 mm per pole enclosures. The 1+N form factor occupies two modules — one for the line pole (overcurrent + residual) and one for the switched neutral. Wiring in and out via tunnel terminals; torque to the value marked on the device side.