The Siemens 5SU9356-8CN25 is a 1+N-pole RCBO (residual current circuit breaker with overcurrent protection) rated 25 A with a 6 kA breaking capacity. It carries a D tripping characteristic and type A residual current sensitivity, from the Construction line — a range built for commercial and light industrial distribution boards where space is tight and coordination with upstream devices matters.
What the ratings mean for fit
The D characteristic means the magnetic trip operates at 10–20× In (250–500 A), so it tolerates the high inrush of motor loads, transformers, or discharge lighting without nuisance tripping — sized for circuits where the starting surge would otherwise pop a B or C curve breaker. Type A residual detection catches pulsating DC fault currents (typical from rectified loads like switched-mode supplies, LED drivers, or VFD front-ends) that a plain AC-sensitive RCD would miss. The 6 kA breaking capacity (Icn) at 230/400 V is the standard for final subcircuits in most commercial panels; it interrupts a bolted fault up to that level without welding the contacts. The 1+N form factor — switching both line and neutral, with overcurrent protection on the line pole only — fits the common single-phase final-circuit layout in European-style distribution boards.
Panel integration
Snap-on DIN rail mount, 2-module width (36 mm). The Construction line uses the same busbar comb footprint as the standard 5SY MCBs and 5SM RCCBs, so it slots into an existing distribution board layout without re-drilling or re-bussing. Neutral bar connection on the right-side terminal; line in at top, load out at bottom — standard wiring order for a 1+N RCBO.