The Siemens 5SU9304-7KX16 is a 2-pole RCBO from the SENTRON series — an RCD-operated circuit breaker combining overcurrent and residual current protection in one 18 mm-wide module. It's rated 16 A at 30 °C with a 30 mA Type A residual trip, C-curve magnetic release, and 10 kA breaking capacity per EN 60898 (also rated 10 kA per IEC 60947-2). That 30 mA Type A trip catches pulsating DC fault currents from electronics and single-phase rectifiers — common in modern loads like switched-mode supplies and LED drivers. The C-curve (5-10x In) handles motor inrush and capacitive loads without nuisance trips, while the 10 kA SCCR at 230/400 V means it clears a hard fault without upstream breaker coordination issues in a residential or light commercial panel.
Snaps onto standard DIN rail, one modular width (18 mm). Depth is 77 mm, installation depth 70 mm — fits flush in a 125 mm-tall enclosure with the gland plate clear. Mounting position any, so it works in vertical or horizontal busbar configurations. IP20 bare; once the distribution board is installed with connected conductors it achieves IP40 — fine for enclosed panels, not for washdown zones. Supply feeds from below per the position-of-power-supply-cord spec.
Derating matters here: at 30 °C it carries the full 16 A; at 40 °C it's 15.2 A; at 45 °C it drops to 14.56 A; at 50 °C it's 14.08 A; at 55 °C it's 13.76 A. If your panel ambient runs hot near the top of the enclosure, factor that curve into the load schedule — don't load a 40 °C row at 16 A. Halogen-free and silicon-free construction, overvoltage category III, pollution degree 2. Touch protection is built in. Energy limitation class 3 — fast arc quenching limits let-through energy, which helps with downstream coordination on a 10 kA fault.