The Siemens SENTRON 5SU9356-8CN06 is a 2-pole RCBO (RCD-operated circuit breaker) combining overcurrent protection with residual current detection in a single 36 mm wide module. Rated 6 A with a D tripping characteristic and 30 mA Type A residual current sensitivity, it's built for circuits where high inrush currents — motor starts, transformer energization, lighting ballasts — would nuisance-trip a B or C curve. The 6 kA breaking capacity per EN 60898 covers most sub-distribution fault levels; the Type A residual current element catches pulsating DC fault currents that a basic Type AC would miss.
What the ratings mean for your panel
The D-curve (tripping characteristic class D) means the magnetic trip fires between 10× and 20× In — so 60 to 120 A instantaneous — which is why this breaker is the go-to for motor feeders, solenoid valve banks, and UPS input circuits where startup current can hit 8–12× running load. The 30 mA trip threshold (tripping fault current rated value 30 mA) provides personal protection against direct contact; it's the standard for socket-outlet circuits in most IEC countries. Type A residual current detection means it responds to sinusoidal AC faults and pulsating DC faults up to 6 mA smooth DC superimposed — critical for modern electronics with half-wave rectification (SMPS, LED drivers, washing machine controllers). Thermal derating is real on this unit: at 40 °C ambient the 6 A rating drops to 5.64 A, at 50 °C it's 5.22 A, and at 55 °C it's 4.86 A. If your panel runs hot — say a packed enclosure with drives — size the upstream protection for the derated figure, not the nameplate 6 A. The insulation voltage (Ui) is rated 264 V, and overvoltage category III suits fixed-installation distribution boards downstream of the main panel. Surge voltage resistance is 4000 V, which covers most industrial transient environments.
Mounting and integration
Two modular width units (36 mm wide) snap onto standard DIN rail. Depth is 77 mm, installation depth 70 mm — check your enclosure depth if you're retrofitting into a shallow gland box. Mounting position is any, so horizontal or vertical busbar feeds are fine; the supply can enter from top or bottom. The IP20 rating applies only when the distribution board is installed with connected conductors — this is a panel-internal device, not a weatherproof field unit. Touch protection is built in (product feature touch protection yes). Pollution degree 2 (non-conductive dust only) is typical for clean industrial or commercial environments.