The C125H420FM is a 4-pole, 1250 A fixed-mount circuit breaker from the ComPacT NS new generation range, built for distribution duty in industrial and commercial switchboards. Its MicroLogic 2.0 electronic trip unit provides L (long-time overload) and I (instantaneous short-circuit) protection, with a 20-minute thermal memory that prevents nuisance reclosing on a hot breaker after a fault clears.
Fixed-mount on a backplate, with front-front connections (upside and downside both front) and a 70 mm connection pitch — standard for panel builder layouts where busbar and cable entry are on the same face.
Durability and electrical life
Electrical durability depends on load: 2,000 cycles at full rated current (1250 A) at 690 V, 3,000 cycles at half current at 690 V, and up to 5,000 cycles at half current at 440 V. For a distribution breaker that's not cycled daily, that's a long service life — but if your application involves frequent switching (like a capacitor bank or welding line), factor the electrical endurance curve into your maintenance schedule.