What it is and what it does
The Siemens SENTRON 5SM9633-0 is an electronic residual current (RC) unit designed to snap onto a 5SL4 miniature circuit breaker, creating a combined RCBO assembly. It handles a rated current of 40 A and trips at 300 mA residual current, type AC (sensitive to sinusoidal AC fault currents). The unit occupies 3 modular width units (54 mm) on a standard DIN rail and is rated for a supply frequency of 50 Hz.
Breaking capacity and standards
The assembly's short-circuit breaking capacity is rated at 6 kA per EN 60898 and IEC 61008-1, which covers the majority of residential and light commercial distribution boards. Overvoltage category III means it's rated for fixed-installation downstream of the utility meter.
Mounting and panel fit
Standard rail mounting in any position. Depth is 70 mm, width 54 mm (3 MW), height 100 mm. The RC unit mounts above the MCB — power supply cord connects at the top. IP20 rating applies once the distribution board is installed with conductors connected; the unit itself is not sealed for wet environments.