The Siemens 5SU1353-1KV32 is a combined residual-current device (RCD) and miniature circuit breaker (MCB) — an FI/LS-protector — in a single 1+N-pole package. It carries a Type AC (WS) trip characteristic for sinusoidal AC fault currents, rated at 30 mA sensitivity and 4.5 kA breaking capacity, with a C-curve overcurrent trip at 32 A.
The 4.5 kA breaking capacity (Icn) means the device can safely interrupt a short-circuit fault up to 4.5 kA without welding contacts or arcing over; that is the typical fault level at the sub-distribution board in most European TN and TT systems. The C-curve (32 A) means the magnetic trip activates at 5 to 10 times rated current — suited for circuits with moderate inrush, like small motors, lighting banks, or socket outlets feeding power tools.