The Siemens 5SU1154-1KV16 is a combined residual-current device and miniature circuit breaker — an FI/LS protector — in a single 1+N-pole module. The C-curve 16 A overcurrent trip handles motor-starting inrush and general-purpose branch circuits up to 16 A, while the 10 mA residual-current element (Type AC, sinusoidal only) catches the leakage a person or livestock would receive in a direct line-to-ground fault. The 70 mm width (D=70 mm) is a standard 4-module DIN-rail footprint, so it occupies four adjacent 18 mm slots in a consumer unit or sub-distribution board. The Type AC designation means it detects only sinusoidal AC residual currents — not pulsed DC or smooth DC — so it is suitable for circuits without electronic loads that generate DC fault components.
Snap-on DIN-rail mounting for standard 35 mm rail in a distribution board or enclosure. The 1+N-pole arrangement switches the line conductor and provides a switched neutral — the neutral pole is not overload-protected but is switched with the line for isolation. The 10 mA sensitivity is below the 30 mA threshold used for general socket-outlet protection in most IEC 60364 installations, so this unit is typically specified for circuits where a lower trip threshold is required — such as wet rooms, medical locations, or equipment that demands a higher touch-voltage safety margin.