What it is and what it does
The Siemens 5SU9304-7KK10 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's a 1P+N design (switches the line, monitors both line and neutral) with a C-curve tripping characteristic, rated 10 A at 30 °C and breaking 10 kA per EN 60898. That 10 kA SCCR means it can safely clear a fault up to that level without welding its contacts or cascading damage upstream — standard for final subcircuits in commercial and light industrial panels.
Thermal derating — the real current you get
The 10 A rating holds at 30 °C ambient. At 40 °C it's 9.4 A; at 45 °C it's 9.1 A; at 50 °C it's 8.7 A; at 55 °C it's 8.1 A. If your panel runs hot — say a crowded enclosure near a motor drive — size the load to the derated figure, not the nameplate 10 A. The 5SU9304-7KK10 also carries a 1 kA surge current withstand at 8/20 μS, which covers most lightning-induced transients on a TN system.
Panel fit and mounting
Snaps onto standard DIN rail, 18 mm wide (1 modular width unit). Depth is 77 mm, installation depth 70 mm — leaves room for wiring behind the gland plate. Mounting position is any orientation; supply can feed from top or bottom. IP20 rated once installed in a distribution board with conductors connected — so it's strictly for enclosed panels, not standalone outdoor use. Pollution degree 2 and overvoltage category III, which is the usual spec for fixed-installation final circuits.