The Siemens 5SU1156-7KV10 is a combined residual-current device and miniature circuit breaker — an FI/LS-protector — in a single 1+N-pole module. It integrates Type A earth-leakage detection (sensitive to pulsating DC residual currents up to 10 mA) with a C-curve overcurrent trip set at 10 A, all within a 70 mm wide DIN-rail housing. The 10 mA residual sensitivity (IΔn) is the key differentiator here: it is far more sensitive than the typical 30 mA RCD used for socket-outlet protection. A 10 mA device is specified for circuits where even a small leakage current poses a risk — for example, in medical locations, wet areas, or circuits supplying equipment with low leakage tolerance. The Type A classification means it detects both sinusoidal AC residual currents and pulsating DC residuals, which covers most modern electronic loads (switched-mode power supplies, variable-speed drives, LED drivers) that generate half-wave fault currents.
Deployment context
The 1+N-pole format (switched phase plus switched neutral) is common in UK and European final-circuit installations where the neutral is isolated when the device trips, ensuring full disconnection.