The Schneider Electric C40F42D250 is a ComPacT NSX moulded-case circuit breaker on the NSX400F frame, 4-pole, rated 250 A at 40 °C. It carries a MicroLogic 2.3 electronic trip unit with L-So-I protection: long-time overload, short-time short-circuit with fixed delay, and instantaneous short-circuit. The 40 kA Icu at 240 V AC (36 kA at 415 V, 30 kA at 440 V, 20 kA at 525 V, 10 kA at 690 V) means it safely interrupts fault currents up to those levels without upstream cascade — sized for distribution panels where high available fault current is a given.
Trip unit and protection logic
That matters for motor or transformer feeders where repeated inrush can nuisance-trip a plain thermal breaker. The L (long-time) curve handles overload, So provides a fixed-delay short-time window for selective coordination downstream, and I clears instantaneous faults. No earth-leakage module on this variant.
Dimensions: 255 mm high, 185 mm wide, 110 mm deep. Front connections both top and bottom. IP40 enclosure protection, IK07 impact resistance. Six accessory slots on the left-side neutral position give room for shunt trips, aux contacts, or motor mechanisms.
Overvoltage category III, utilisation category A. Relative humidity 0–95 %. The breaker carries UL 60947-4-1 listings for the North American market with 85 kA Icu at 240 V AC, 35 kA at 480 V, 20 kA at 600 V.