What this RCBO does on the rail
The Siemens 5SU9304-0KK32 is a 1P+N RCBO from the SENTRON family — a combined residual-current device and miniature circuit breaker in one 18 mm-wide module. It protects a single-phase final subcircuit against overload, short-circuit (B-curve, 10 kA per EN 60898 and IEC 60947-2), and earth leakage (Type AC, 30 mA sensitivity). The neutral is switched and solid, with a 600 mm factory-attached pigtail for the N connection. It occupies one modular-width unit on the DIN rail, so it fits standard distribution boards without crowding the gland plate. Rated operational voltage is 230/240 V AC at 50/60 Hz. The B-curve means magnetic trip occurs at 3–5× In (96–160 A for this 32 A unit), which suits resistive and general-purpose loads — lighting, small heaters, socket circuits — where inrush is modest. The 30 mA residual sensitivity catches direct-contact leakage and protects against fire risk from tracking faults.
Mounting and integration
Snap-on DIN rail mount, any orientation. The 18 mm width and 77 mm depth leave clearance in standard 125 mm-tall enclosures; the 70 mm installation depth accounts for the pigtail bend radius behind the rail. Supply can enter from top or bottom — no mandatory orientation. IP20 rating applies once the distribution board is installed and conductors are connected; the device itself is not rated for washdown environments. Halogen-free and silicon-free construction matters for panels in clean-room or corrosive-gas environments — no outgassing that could tarnish contacts or optics nearby. Mechanical service life is rated at 10,000 operating cycles typical, sufficient for most fixed-installation switching duties.
Selectivity and coordination notes
Overvoltage category III and pollution degree 2 mean it is rated for fixed-installation mains distribution, not for outdoor or wet locations. The 4 kV surge voltage resistance and 1 kA surge current (8/20 µs) give it reasonable immunity to lightning-induced transients on the supply side. Energy limitation class 3 indicates it limits let-through energy to a level that protects downstream wiring in a fault condition. Power dissipation per pole at rated current in hot operating state is 0.75 W — negligible for thermal management in a populated enclosure, but worth summing across multiple RCBOs in a dense board to avoid internal temperature rise above the 75 °C maximum.