The Siemens 5SU1653-1KV16 is a combined residual-current device (RCD) and miniature circuit breaker (MCB) — an FI/LS protector — in a single 70 mm wide unit. It delivers type AC residual-current detection at 300 mA and a C-curve overcurrent trip at 16 A, with a 4.5 kA breaking capacity. This is a 1+N-pole configuration: phase and neutral are switched, protecting single-phase circuits up to 230 V AC.
Snap-mounts onto standard DIN rail in the distribution board. The 70 mm width (4 module spaces) fits alongside standard MCBs and RCCBs. Type AC detection handles sinusoidal AC residual currents — suited for general-purpose circuits in residential and light commercial panels where no electronic loads (rectifiers, inverters) are present on the protected branch.
The C-curve (16 A) trips between 5× and 10× rated current, designed for circuits with moderate inrush — lighting banks, small motors, pumps. The 300 mA residual threshold is less sensitive than the common 30 mA type, reducing nuisance tripping on circuits with natural leakage (long cable runs, multiple loads) while still providing fault protection. Breaking capacity of 4.5 kA is adequate for most domestic and commercial sub-distribution boards where the prospective short-circuit current is below that level.