The Siemens 5SU9346-1CN50 is a 4-pole RCD-operated circuit breaker from the SENTRON 5SU9 series. It combines overcurrent protection with residual current detection in a single DIN-rail module, rated for 50 A at 30 °C with a C tripping characteristic and a 6 kA breaking capacity per both EN 60898 and IEC 60947-2. This is an instantaneous-type device for AC fault currents, covering 4 poles with protection on all poles. The C curve handles moderate inrush from motor and lighting loads.
DIN-rail fit and wiring
Occupies 7 width units (126 mm wide) on the DIN rail, with a 77 mm depth and 70 mm installation depth. The 90 mm height fits standard distribution boards. Mounting position is unrestricted — any orientation works. Terminals accept solid or stranded conductors from 0.75 mm² up to 35 mm². Supply can enter from top or bottom. IP20 rating applies only when the distribution board is installed and conductors are connected. Touch protection is built in. Power dissipation maxes at 2.25 W under full load — factor that into enclosure thermal calculations if the panel is densely packed.
Thermal derating — the real current rating
The 50 A rating holds at 30 °C ambient. At 40 °C it derates to 46.5 A, at 45 °C to 44.5 A, at 50 °C to 43.5 A, and at 55 °C to 42.5 A. If your panel runs warm — and most do — size the load against the derated figure for your actual ambient. Ambient operating range is -25 to +45 °C; storage range extends from -40 to +75 °C. That storage spec governs handling and warehousing, not running conditions.