What it is and what it does
The Siemens 5SU1656-0KV16 is a combined residual-current device and miniature circuit breaker — an FI/LS protector — in a single 1+N-pole module. It combines Type AC (sinusoidal AC fault detection) with a B-curve overcurrent trip at 16 A, a rated residual operating current of 300 mA, and a short-circuit breaking capacity of 6 kA. The 70 mm wide housing snaps onto DIN rail, so it fits standard consumer units and distribution boards.
What the ratings mean for fit
The B-curve 16 A overcurrent trip means the magnetic release operates at 3 to 5 times rated current (48–80 A), suited for resistive and moderate inductive loads like lighting, socket outlets, and small motor circuits. The 300 mA residual-current threshold is a delayed or selective trip level — it provides fire protection and equipment protection rather than personal shock protection (which typically requires 30 mA). The 6 kA breaking capacity at 1+N-pole is adequate for domestic and light commercial distribution boards where the prospective short-circuit current stays under that level. Type AC detection covers sinusoidal AC faults only; if the installation includes non-sinusoidal loads (VFDs, switched-mode supplies), a Type A or Type F device would be required.