The Siemens 5SV9313-1CN25 is a 1P+N RCD-operated circuit breaker from the SENTRON 5SV9 series — a combined overcurrent and residual current device (RCBO) in a single 18 mm wide module. For a domestic or light commercial distribution board fed from a transformer of similar kA rating, this is the standard coordination point.
Thermal derating and conductor sizing
Per the datasheet, at 40 °C it's 23.75 A, at 45 °C it's 23 A, at 50 °C it's 22.25 A, and at 55 °C it's 21.5 A. If the distribution board runs warm — say, above 40 °C — the load must be reduced accordingly.
Width is 18 mm (1 width unit), height 90 mm, depth 77 mm with an installation depth of 70 mm. Supply can enter from either top or bottom. Power dissipation is rated at a maximum of 1.5 W, which is low enough that thermal buildup in a densely populated enclosure is manageable.