What the ratings mean for the panel
The ABB S801S-K25 is a 1-pole miniature circuit breaker from the S800S series, rated at 25 A with a Trip Curve K characteristic. That K-curve means it's designed for inductive loads — motors, transformers, solenoid valves — where the inrush current is higher than a resistive load but not as extreme as a motor-start. The magnetic trip threshold sits between 8 and 12 times rated current, so it holds through a motor's starting surge but clears a hard fault fast. The 50 kA interrupting rating at 230 VAC is the headline number here. That's the fault current this breaker can safely interrupt without welding contacts or venting plasma. For a panel fed by a transformer with high short-circuit capacity — say, a 630 kVA unit close-coupled — that 50 kA rating means the S801S-K25 can sit downstream without needing a current-limiting fuse upstream. Most 1-pole MCBs in this form factor top out at 6–10 kA; this one handles an order of magnitude more. Mounting is standard DIN rail (35 mm per EN 60715), so it clips into any panel enclosure. The 1-pole form factor means it occupies one module width — roughly 17.5 mm — which matters when you're packing 24 circuits into a 600 mm wide cabinet.