What this part is and what it does
The Siemens 5SU1354-1KV32 is an FI/LS combination unit — an RCD and MCB in one DIN-rail module — rated 30 mA residual-current sensitivity (Type AC, waveform-sensitive) and 10 kA breaking capacity, 1+N-pole, C-curve 32 A. Type AC means it detects sinusoidal AC residual currents only; for pulsed DC or mixed-frequency faults you would need a Type A or Type F variant. The C-curve trip characteristic (5–10× In) suits it for loads with moderate inrush, such as motor-driven pumps or compressors in a panel.