RCD-operated circuit breaker — 32 A, Type A, C-curve
The Siemens 5SU9304-7KX32 is a SENTRON RCBO — an RCD-operated circuit breaker combining overcurrent and residual current protection in a single 18 mm wide module. Rated 32 A at AC with a C tripping characteristic, it handles moderate inrush from motor starters and lighting banks without nuisance trips. The Type A fault-current detection catches pulsating DC residual currents from rectified loads (VFDs, switched-mode supplies) that a plain AC type would miss. Breaking capacity is 10 kA per EN 60898 and IEC 60947-2, so it safely interrupts fault currents up to that level in a 230/400 V distribution board. The 1P+N configuration switches the live pole and monitors the neutral; the neutral is not switched, which matches standard single-phase final circuits in European panel builds.
Thermal derating and installation
Rated current holds at 32 A up to 30 °C ambient; above that it derates stepwise — 30.4 A at 40 °C, 29.12 A at 45 °C, 28.16 A at 50 °C, 27.52 A at 55 °C. The operating ambient range is -25 to +45 °C, storage -40 to +75 °C. Mounting position is any, installation depth 70 mm, overall depth 77 mm. Conductor cross-section accepts 0.75 to 35 mm² solid or stranded. Protection class is IP20 with the distribution board installed; with connected conductors it achieves IP40. Overvoltage category III suits fixed-installation downstream of the main distribution board. Energy limiting class 3 means it limits let-through energy well for downstream equipment protection.