The Siemens 5SU9356-7KN25 is a 1P+N RCD-operated circuit breaker (RCBO) from the SENTRON 5SU9 series, combining overcurrent and residual-current protection in a single 36 mm-wide (2 MW) module. The Type A fault-current detection catches pulsating DC and AC residual currents — common on single-phase electronics, variable-speed drives, and switching power supplies.
Ratings that matter for panel fit
Rated current is 25 A at 30 °C ambient, but the thermal derating curve is worth noting: at 40 °C it's 23.5 A, at 45 °C it's 22.75 A, and at 55 °C it drops to 20.25 A. If your panel runs warm — say, a packed enclosure with multiple breakers — size the load side accordingly. Solid and stranded conductors from 0.75 to 35 mm² are accepted — that covers everything from 1.5 mm² lighting circuits up to 10 mm² feeder tails.
The 5SU9356-7KN25 carries IP20 protection (finger-safe, with conductors connected and distribution board installed). Touch protection is built in. The design references EN 60898 and IEC 60947-2 for breaking capacity, and the component function code is F per DIN EN 61346-2 and DIN EN 81346-2.