The Siemens 5SU9346-1CN25 is a 4-pole RCD-operated circuit breaker (RCBO) from the SENTRON 5SU9 series, combining overcurrent protection and residual current detection in a single DIN-rail mounted unit. The RCBO detects AC fault currents only (Type AC) and trips instantaneously — no time delay, so it reacts to earth faults without intentional lag. That means it's suited for general-purpose circuits where nuisance tripping from transient leakage is unlikely, but not for circuits with downstream electronics that generate smooth DC fault currents.
At 40 °C it derates to 23.3 A, at 45 °C to 22 A, at 50 °C to 21.5 A, and at 55 °C to 20.8 A. Size the upstream protective device and cable accordingly. Terminals accept solid or stranded conductors from 0.75 mm² up to 35 mm² — covers everything from 1.5 mm² lighting circuits to 10 mm² feeder tails. The 77 mm depth and 70 mm installation depth fit standard 80 mm deep enclosures; the 126 mm width (7 modular width units) means it occupies 7 x 18 mm on the DIN rail.
Halogen-free and silicon-free construction means it meets the material restrictions common in rail, marine, and high-reliability building specs. Touch protection is built in — no separate finger-safe covers needed after installation.
IP20 rating applies only when the distribution board is installed and conductors are connected; the front face is finger-safe, but the terminals are not sealed against dust ingress before wiring.