The Siemens 5SU1653-7KV20 is a combined residual-current and overcurrent protective device — an FI/LS protector — in a single 1+N-POL module. It carries a C-curve 20 A overcurrent trip, a 300 mA Type A residual-current sensing circuit, and a 4.5 kA short-circuit breaking capacity. The D=70 mm housing width matches standard Siemens modular devices for DIN-rail panels.
What the ratings mean on site
Type A residual-current detection means it catches pulsating DC fault currents from single-phase rectifier loads (switched-mode supplies, LED drivers, variable-speed drives) in addition to sinusoidal AC faults. The 300 mA sensitivity is the standard for fire protection and general shock prevention in fixed installations — not the 30 mA personal-protection threshold, so this unit is sized for sub-distribution or equipment-level protection where the loop impedance and leakage profile allow a higher trip level. The C-curve 20 A overcurrent element handles moderate inrush from motorized or capacitive loads without nuisance tripping, while the 4.5 kA breaking capacity suits domestic or light commercial panels where the prospective fault current stays under that level.