What it is and what it does
The Siemens 5SU9356-1KK50 is a SENTRON RCBO — an RCD-operated circuit breaker that combines overcurrent protection and residual-current detection in a single 2-module-width (36 mm) package. It's a 1P+N design, meaning it switches and protects the live conductor only, with a switched neutral that follows the pole. Rated 50 A at 30 °C with a C tripping curve, it handles the inrush from motor starters and transformer banks without nuisance trips, while still clearing fast on a hard short.
Breaking capacity — what the numbers mean
This RCBO carries two breaking-capacity ratings: 6 kA according to EN 60898 and 10 kA according to IEC 60947-2. The EN 60898 figure is the standard for household and similar installations — it's the rating that applies when the device is used as a domestic-grade MCB/RCD combo. The IEC 60947-2 rating is the industrial equivalent, tested to a higher standard for fault-clearing in industrial panels. If your panel spec calls out 10 kA SCCR at the branch, the 60947-2 number is the one that satisfies it. The 6 kA rating is fine for residential or light commercial where the prospective fault current is lower.
Temperature derating — don't ignore it
The 50 A rating is at 30 °C ambient. At 40 °C it's 47.5 A; at 45 °C it's 46.5 A; at 50 °C it's 45 A; at 55 °C it's 43.5 A. If this RCBO sits in a crowded panel with other heat sources, the actual continuous current it can carry without tripping drops. A 50 A breaker in a 50 °C enclosure is really a 45 A device. Factor that into your load calculation or you'll get nuisance trips on a hot day.
Mounting and integration
Snaps onto standard DIN rail. Installation depth is 70 mm; overall depth is 77 mm. The 36 mm width (2 MW) means it takes up two 18 mm slots. Supply can come from either top or bottom — no forced orientation. Mounting position is any, so you can lay it sideways in a shallow enclosure if needed. IP20 with the distribution board installed and conductors connected — that's touch-finger protection only, not for wet or dusty locations.