The C25W42D100 is a Schneider ComPacT NSX moulded-case circuit breaker, 4-pole, rated 100 A at 40 °C with a MicroLogic 2.2 electronic trip unit. The 100 kA Icu at 690 V AC (also rated 100 kA at 500 V and 525 V) means it can interrupt a fault current up to that level without failing — essential for high-fault-capacity distribution boards where upstream transformers can deliver tens of kiloamps into a bolted short. The electronic trip gives you LSI protection: long-time overload (L), short-time short-circuit with fixed delay (So), and instantaneous short-circuit (I). The 20-minute thermal memory before and after tripping means the breaker remembers prior heating, so it won't reclose into a still-hot conductor and nuisance-trip again — useful on motor or transformer feeders that draw high inrush.
Mounts on a backplate — no DIN rail here. The 35 mm connection pitch and front-facing connections (both upside and downside) keep wiring accessible. It sits in any orientation: horizontal, vertical, or flat on the back. IP40 front face keeps out tools and fingers; IK07 impact rating means it survives a 2 J knock during panel assembly.
Utilisation category A (no intentional short-time delay for selectivity with downstream breakers — the So protection provides a fixed short-time delay within the breaker itself). Electrical durability: 20,000 cycles at 440 V In/2, 10,000 at 440 V In, 10,000 at 690 V In/2, 5,000 at 690 V In. Mechanical durability: 20,000 cycles. Neutral on the left, toggle control, 50/60 Hz network. Operating altitude 0–2000 m without derating, 2000–5000 m with derating.