What this RCBO is and what it does
The Siemens 5SU9304-7KK32 is a SENTRON RCBO — a residual-current-operated circuit breaker that combines overcurrent protection and earth-leakage detection in a single 1-module-width (18 mm) package. It is rated 32 A at 30 °C with a 30 mA residual-current trip threshold, Type A (pulsating DC and sinusoidal AC), C-curve magnetic trip characteristic, and a 10 kA breaking capacity per EN 60898. This is the variant with two poles switched but only one pole protected against overcurrent — the neutral pole is switched but not monitored for overload. The C-curve means the magnetic trip operates at 5 to 10 times rated current — suited for mixed resistive-inductive loads where moderate inrush is expected, like small motors, lighting banks, or control transformers. The 30 mA trip threshold catches leakage currents that could be hazardous to personnel, while the Type A detection handles the rectified waveforms common in modern electronics.
Temperature derating — the real-world current rating
The 32 A rating holds at 30 °C ambient. At 40 °C it derates to 30.08 A; at 45 °C to 29.12 A; at 50 °C to 27.84 A; and at 55 °C to 25.92 A. If the panel ambient runs warm — common in a crowded enclosure — the actual continuous current the RCBO can carry without nuisance tripping is lower than the label. Plan the load at the derated figure for the expected cabinet temperature.
Panel fit and mounting
Snap-on DIN rail mount, 1 module width (18 mm), 77 mm depth, 125 mm height. Installation depth is 70 mm. Supply can enter from top or bottom. Touch protection is built in. Rated IP20 once installed in a distribution board with conductors connected — this is a panel-interior device, not for wet or dusty locations. Pollution degree 2, overvoltage category III. Halogen-free and silicon-free construction.