What it is and what the ratings mean for fit
The Siemens SENTRON 5SU9304-1KK10 is a combined RCD and MCB in one 18 mm-wide module — an RCBO (residual-current-operated circuit breaker) that saves a DIN-rail position compared to a separate RCD + MCB pair. It protects a single-phase final subcircuit against both overload/short-circuit (C-curve, 10 A rated) and earth leakage (30 mA, Type AC). The C-curve means the magnetic trip operates at 5 to 10 times In (50–100 A), suited for mixed resistive and moderate inductive loads like lighting, small motors, or socket outlets. The 30 mA sensitivity is the standard for personal protection against indirect contact in residential and commercial installations. The 10 kA breaking capacity per EN 60898 tells you it can safely interrupt a fault current up to 10 kA at the rated voltage — adequate for most domestic and light commercial distribution boards where the prospective short-circuit current stays below that level.
Derating and installation constraints
The 10 A rating holds at 30 °C ambient. At 40 °C it derates to 9.4 A, at 45 °C to 9.1 A, at 50 °C to 8.7 A, and at 55 °C to 8.1 A (–). If the distribution board runs warm — say, tightly packed with other breakers — you need to account for that derating or up-size the breaker. The module occupies one 18 mm modular width and installs on a DIN rail in any mounting position. Supply can enter from top or bottom. The IP20 rating applies only when the distribution board is installed with conductors connected — so it's not a standalone outdoor device. Depth is 77 mm, installation depth 70 mm; verify gland-plate clearance in shallow enclosures.