The Schneider Electric C25R42D100 is a ComPacT NSX circuit breaker from the ComPacT range, rated 100 A at 40 °C with a MicroLogic 2.2 electronic trip unit. It is a 4-pole (4P) device with a breaking capacity of 200 kA Icu at 415 V AC, certified to EN/IEC 60947-2. This is the part you spec when you need a 100 A frame with serious fault current headroom — the 200 kA rating at 415 V means it can sit upstream of a high-capacity transformer or generator bus without worrying about cascading failure. The electronic trip unit gives you L (long-time overload), So (short-time short-circuit with fixed delay), and I (instantaneous) protection curves, all adjustable via the front interface.
At 690 V AC it still holds 45 kA Icu, which is relevant for 690 V distribution in mining or marine installations. For a site electrical engineer coordinating selectivity with downstream breakers, the 200 kA figure at 415 V gives you headroom to set the instantaneous trip higher, keeping nuisance trips off the main while still protecting the bus. The MicroLogic 2.2's So function (short-time with fixed delay) lets you cascade with downstream devices rated at lower SCCR, as long as the let-through energy is coordinated.
The 35 mm connection pitch matches standard DIN-rail terminal blocks for the load and line side. Front connections on both upside and downside simplify panel wiring and busbar alignment. The toggle control is manual; no motor operator or rotary handle is included in this order code. Five accessory slots are available for shunt trips, auxiliary contacts, or undervoltage releases.
Trip unit and protection
The protection functions are: L (long-time overload, adjustable), So (short-time short-circuit with fixed delay, adjustable), and I (instantaneous short-circuit, adjustable). The electronic design gives better accuracy and repeatability than a thermal-magnetic breaker, especially for low-level overloads where a bimetallic strip drifts with ambient temperature. The flashing green LED signals 'ready to operate'; red LED at 105 % Ir indicates overload; orange LED at 90 % Ir warns of approaching overload. This is useful for a field service tech doing a quick visual check without opening the panel door.