The Siemens 5SU9304-1KK20 is a SENTRON RCBO — an RCD-operated circuit breaker combining overcurrent and residual-current protection in a single 1 MW (18 mm) module. Rated 20 A at 30 °C with a C tripping curve, it breaks 10 kA per EN 60898 and IEC 60947-2, covering most residential and light commercial final circuits. The 1P+N design protects the live conductor only; the neutral is switched but not protected.
What the ratings mean for fit
The 20 A rating at 30 °C derates to 18.8 A at 40 °C and 16.2 A at 55 °C — if the distribution board sits in a hot attic or near a boiler, size the upstream MCB accordingly. The C-curve (magnetic trip at 5–10× In) suits motor and lighting loads with moderate inrush; for purely resistive circuits a B-curve would trip faster. The 10 kA breaking capacity at 230/240 V matches the typical prospective short-circuit current at the service entrance in most European domestic installations. The 1 MW width (18 mm) and 77 mm depth fit standard DIN-rail enclosures; the 70 mm installation depth leaves room behind the gland plate. Operating temperature spans -40 °C to 75 °C, so it handles outdoor cabinets and unheated plant rooms. The IP20 rating applies only when the distribution board is installed and conductors are connected — not for open-panel use. Halogen-free and silicon-free construction matters for clean-room or high-reliability environments where outgassing contaminates optics or contacts.
Panel integration notes
Mounts in any position on a 35 mm DIN rail. The 1 MW width (18 mm) means it occupies one slot in a standard modular enclosure. Supply can enter from top or bottom — no orientation restriction. The test button requires a minimum 115 V to function; verify the test circuit voltage before commissioning.