The 5SU1653-1KV25 is a Siemens FI/LS combination unit — an RCBO that packs both overcurrent protection and residual-current detection into a single 1+N-pole module, 70 mm wide on the DIN rail. The C-curve 25 A thermal-magnetic trip handles motor-starting inrush and moderate inductive loads without nuisance tripping; the 300 mA Type AC residual element catches sinusoidal AC earth faults.
Deployment context
The 70 mm width occupies four standard 17.5 mm DIN-rail modules in a consumer unit or sub-distribution board. Type AC detection means it is intended for sinusoidal AC residual currents — not pulsed DC or smooth DC fault types, so it suits general lighting and socket-outlet circuits but not equipment with rectifiers or VFDs that generate DC fault components.