What it is and what it does
The Siemens 5SU1353-0KV32 is a combined residual-current and miniature circuit breaker (RCBO) — one unit does both jobs: ground-fault protection and overcurrent/short-circuit protection. It's a Type AC device, meaning it detects sinusoidal AC residual currents only, not pulsating DC or smooth DC. The 30 mA trip threshold is the standard for personal protection against electric shock in residential and commercial final circuits. Rated at 32 A with a B-curve magnetic trip, so it's sized for general-purpose socket outlets and lighting circuits where the inrush isn't severe — think resistive and light inductive loads, not motor starting. The 4.5 kA breaking capacity (Icn) covers the typical domestic or light commercial fault level, but it's worth checking the prospective short-circuit current at the installation point.
Mounting and integration
Snaps onto a standard 35 mm DIN rail in the distribution board. The 1+N-pole format switches the line conductor and disconnects the neutral, which is the usual arrangement for single-phase final circuits in TN and TT systems. 70 mm deep — check the enclosure depth before committing; some shallow consumer units are tight.