What it is and what it does
The Siemens 5SU9356-1KN50 is a 2-pole RCD-operated circuit breaker (RCBO) from the SENTRON family, combining overcurrent protection and residual current detection in one 36 mm-wide module. It's rated 50 A at 30 °C with a 30 mA Type AC residual current trip and a C tripping characteristic — the standard choice for general-purpose socket circuits and mixed resistive-inductive loads in commercial and residential distribution boards. Rated breaking capacity is 10 kA per IEC 60947-2 and 6 kA per EN 60898, covering most sub-distribution fault levels. The C-curve means magnetic trip occurs at 5 to 10 times rated current — suited for loads with moderate inrush like small motors, lighting banks, and power supplies.
Sizing and derating
Full 50 A rating holds at 30 °C ambient. Derate to 47.5 A at 40 °C, 46.5 A at 45 °C, 45 A at 50 °C, and 43.5 A at 55 °C — important when the breaker sits in a crowded enclosure with other heat sources. Operating range spans -40 °C to 75 °C, so it handles unheated utility rooms and outdoor-adjacent installs.
Panel fit and wiring
Occupies 2 modular width units (36 mm) on standard DIN rail. Depth is 77 mm (70 mm installation depth), height 90 mm. IP20 rating applies when installed in a distribution board with conductors connected. Touch protection is built in. Halogen-free and silicon-free construction suits environments sensitive to outgassing — clean rooms, medical facilities, or telecom shelters.