The C25F4TM125C is a Schneider Electric ComPacT NSX250F moulded-case circuit breaker (MCCB) with a 125 A thermal-magnetic TM-D trip unit, 4 poles, and an F breaking capacity code — 36 kA Icu at 380/415 V AC 50/60 Hz per IEC 60947-2. That 36 kA figure at 415 V is the one that governs most European and Asian distribution panels; the breaker also carries 85 kA Icu at 240 V and 8 kA at 690 V, so it's usable across a wide voltage range without swapping frames.
The TM-D trip unit combines thermal overload (L) and fixed magnetic short-circuit (I) protection — no electronic adjustment, no ground-fault module. At 125 A and 50 °C ambient, it's sized for a 100–125 A feeder or a large motor branch circuit where you want simple, field-proven thermal-magnetic coordination. The 4-pole version (4P) switches the neutral as a switched pole with protection set at 1 x Ir (full rated current), which matters for TN-S or IT systems where you need neutral protection. Breaking capacity is voltage-dependent: 85 kA at 240 V, 36 kA at 415 V, 30 kA at 500 V, 22 kA at 525 V, 8 kA at 690 V. If your fault current at the board exceeds 36 kA at 415 V, step up to the NSX250H or NSX250L frame. IP40 enclosure protection means it's suitable for clean indoor panels — no washdown, no dust ingress. The IK07 impact rating (per IEC 62262) means the front cover withstands a 2 J impact, typical for accidental tool drops during maintenance.
Electrical durability: 20,000 cycles at 440 V at half rated current, 10,000 cycles at full rated current.