What it is and what it does
The Siemens 5SU9304-7PK32 is a combined residual-current circuit breaker with overcurrent protection (RCBO) from the SENTRON family — one modular-width unit (18 mm) that packs both an MCB and an RCD into a single 1P+N pole. It protects a single-phase final subcircuit against overload, short-circuit, and earth leakage in one go. Rated at 32 A with a C tripping curve, it handles moderate inrush loads like small motors, lighting banks, and control transformers. The 10 kA breaking capacity per EN 60898 and IEC 60947-2 means it can safely interrupt a fault current up to 10,000 A — enough for most commercial and light-industrial distribution boards. The built-in residual-current element is Type A, 30 mA sensitivity, so it detects both sinusoidal AC ground faults and pulsating DC fault currents — typical for electronics-heavy circuits (switched-mode PSUs, VFDs, LED drivers) where pure AC-only RCDs may not trip.
Where it goes and how it fits
Snaps onto a standard DIN rail in any mounting position. The 18 mm width (1 MW) means it occupies one slot — tight for retrofit panels where space is already allocated. Supply can come from top or bottom, and the solid neutral is switched internally (1P+N). IP20 rated with conductors connected. Installation depth is 70 mm; total depth is 77 mm. Overvoltage category III and pollution degree 2 suit it for fixed installations downstream of the main distribution board — typical in commercial buildings, small workshops, and residential risers.