FI/LS Protector, Type AC, 30 mA, 6 kA, 1+N-Pole, B 20 A
The Siemens 5SU1356-0KV20 is a combined RCD and MCB in a single 1+N-pole module. It integrates Type AC residual-current detection at 30 mA with a B-curve overcurrent trip at 20 A, rated for 6 kA breaking capacity.
What the Ratings Mean for Fit
The 30 mA residual sensitivity (IFN) covers sinusoidal AC fault currents to ground — the standard for general-purpose socket-outlet protection in residential and commercial final circuits. Type AC means it detects pure AC residual currents only; if the load includes rectified or pulsed DC (e.g., VFDs, LED drivers, UPS), a Type A or Type F device would be required. The B-curve 20 A overcurrent characteristic trips between 3 and 5 times rated current (60–100 A), suited for resistive and moderate inductive loads like lighting, small heaters, and general-purpose outlets. The 6 kA breaking capacity (Icn) is the short-circuit withstand at the device's rated voltage — adequate for most domestic and light commercial distribution boards where the prospective fault current stays under 6 kA. The 1+N-pole format switches the line (L) and provides a switched neutral (N) in a single-width (70 mm) module, matching standard DIN-rail enclosures. The neutral pole opens and closes with the line, ensuring isolation on both conductors when the device trips or is manually switched off.
Deployment Context
Snap-on DIN-rail mounting for 70 mm enclosure width. Terminals accept copper conductors per the manufacturer's wiring specification; strip length and torque settings follow the markings on the device housing. The combined RCD/MCB format saves one module width compared to separate devices in series.