What it is and what it does
The Siemens 5SU1653-1KV32 is a combined residual current device (RCD) and miniature circuit breaker (MCB) — an RCBO in one DIN-rail module. It protects a 1+N-POL circuit (single-phase with neutral) at a C-curve 32 A overcurrent rating and a 300 mA residual current trip threshold, Type AC (sensitive to sinusoidal AC fault currents only). Breaking capacity is 4.5 kA. The D=70 mm dimension refers to the overall depth of the device, which matters when fitting into shallow enclosures or gland-plate clearance.
Deployment context
Snap-on DIN-rail mounting for panel integration. The 1+N-POL form factor occupies a single module width on the rail. Type AC detection means it responds to sinusoidal AC residual currents only — suitable for general-purpose socket-outlet circuits, lighting, and resistive loads where no pulsed DC or smooth DC fault currents are expected. The 300 mA sensitivity is a higher threshold than the standard 30 mA for personal protection; this unit is typically selected for equipment or fire protection rather than direct personnel shock protection.