What it is and what the ratings mean
The Siemens 5SU1653-0KV32 is an FI/LS combination device — a residual-current circuit breaker (RCD) and miniature circuit breaker (MCB) in one 1+N-pole unit, saving a DIN-rail position over separate devices. The Type AC (WS) designation means it detects sinusoidal AC residual currents only; it is the standard choice for general-purpose socket circuits and lighting where no pulsed DC or smooth DC fault currents are expected. The 300 mA IΔn (rated residual operating current) is the trip threshold for earth leakage — higher than the 30 mA used for personal shock protection, so this unit is sized for equipment and fire protection rather than direct human contact. The B-curve 32 A overcurrent characteristic trips instantaneously at 3–5× rated current (96–160 A), suited for resistive and moderate inductive loads like lighting banks and small motor circuits. The 4.5 kA breaking capacity at 230/400 V is the maximum prospective fault current the device can safely interrupt; verify the available fault current at the installation point does not exceed this figure.
Integration notes
The 70 mm depth (D=70MM) is the dimension from the DIN-rail mounting surface to the front of the device — check enclosure depth clearance, especially in shallow gland-plate or back-panel layouts. The 1+N-pole format occupies a single module width on the DIN rail; the neutral pole is switched and protected together with the phase. Spring-cage or screw terminals accept 1.5–25 mm² conductors depending on the terminal design; verify the specific terminal range on the device label before terminating.