What it is and what it does
The Siemens 5SU1356-1KV06 is a combined residual current device and miniature circuit breaker — an RCBO, sometimes called an FI/LS protector — in a single 1+N-pole module that snaps onto DIN rail. It's rated C-curve 6 A overcurrent protection with 30 mA residual current sensitivity (Type AC) and a 6 kA breaking capacity. That 30 mA trip threshold is the standard for personal protection against electric shock in residential and light commercial final circuits. The C-curve means it handles moderate inrush from motorized loads like pumps or small compressors without nuisance tripping, while still clearing fast on a hard fault.