What it is and what it does
The Siemens 5SU9304-1KK32 is a SENTRON RCBO — an RCD-operated circuit breaker that combines overcurrent protection and residual-current detection in a single 18 mm-wide module. It is rated 32 A at 30 °C with a 30 mA residual-current trip threshold and a Type C tripping characteristic, meaning it handles moderate inrush loads like small motors or lighting banks without nuisance tripping. The 10 kA breaking capacity per EN 60898 covers most commercial and light-industrial distribution boards. It occupies one modular-width unit (18 mm) on a DIN rail, with a depth of 77 mm and height of 125 mm. The RCBO is designed for 1P+N (switched phase, switched neutral) and is rated for overvoltage category III, pollution degree 2 — standard for fixed-installation distribution panels. Mounting position is any, and the supply cord can enter from either top or bottom. The IP20 rating applies only when the distribution board is installed with connected conductors.
Thermal derating and real-world current
The 32 A rating is at 30 °C ambient. At 40 °C the continuous current drops to 30.08 A; at 45 °C to 29.12 A; at 50 °C to 27.84 A; and at 55 °C to 25.92 A. If the panel runs warm — common in crowded enclosures — the effective capacity is lower than the label. Factor this into the load schedule.