What it is and what it does
The Siemens 5SU1653-6KV16 is a combined residual-current device and miniature circuit breaker (RCBO) — an FI/LS-protector in Siemens' own nomenclature. It integrates Type A residual-current detection (sensitive to pulsating DC fault currents) with a B-curve overcurrent trip into a single 1+N-Pol module, saving a DIN-rail position over separate RCD + MCB. Rated at B 16A for the overcurrent side and 300 mA IΔN for the earth-leakage side, with a 4.5 kA breaking capacity. The 70 mm depth (D=70mm) is the standard for Siemens' 5SU series RCBOs, fitting the same enclosure cutouts as the 5SL MCBs.
Panel integration notes
Snap-on mounting to 35 mm DIN rail per EN 60715. The 1+N-Pol module occupies a single modular width (18 mm per pole, so 36 mm total for the 1+N). Terminals accept 1–25 mm² conductor; strip length 10 mm. The neutral is switched and protected internally — no external neutral bar required downstream of this device. Type A RCD function means it meets the requirements of VDE 0100-530 for circuits where electronic loads can generate pulsating DC fault currents. Common in commercial and light-industrial final subcircuits feeding IT equipment, LED drivers, or small VFDs.