The Siemens 5SU1356-0DV40 is a combined residual-current and miniature circuit breaker (RCBO) — an FI/LS protector in Siemens' own shorthand. It packs a 40 A B-curve overcurrent trip and a 30 mA Type AC residual-current detection into a single 1+N-pole module with a pig-tail neutral connection. The 6 kA breaking capacity covers most residential and light commercial distribution boards where the prospective short-circuit current stays under that threshold.
What the ratings mean for fit
The B-curve (3–5× In magnetic trip) is the standard choice for resistive and general-purpose loads — lighting circuits, socket outlets, small appliances — where inrush isn't a concern. The 30 mA residual sensitivity is the mandatory level for socket-outlet circuits in most IEC 60364-based wiring regulations, providing personal protection against direct contact. The 6 kA rated short-circuit capacity (Icn per EN 60898) means this unit can safely interrupt a fault up to 6 kA without welding its contacts or failing catastrophically; for installations with higher available fault current, you'd need a current-limiting upstream MCB or a higher-rated RCBO. Type AC detection means it responds to sinusoidal AC residual currents only. That covers the vast majority of domestic and office circuits, but not pulsating DC or smooth DC faults — those need Type A or Type F devices. If your load includes variable-speed drives, LED drivers, or single-phase rectifiers, verify the residual waveform before specifying this unit.
Panel integration notes
The 70 mm depth (D=70MM) is the dimension from the DIN-rail mounting surface to the front of the device — standard for Siemens 5SU series RCBOs. The pig-tail neutral connection exits the bottom; plan your wiring channel to accommodate the factory-fitted neutral lead rather than a busbar pickup. The 1+N-pole format occupies a single module width on the DIN rail, matching the standard 18 mm per pole spacing.