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Product Overview & Model Breakdown
C125N420FM is a 4‑pole molded case circuit breaker from Schneider Electric’s ComPacT NS1250N series, equipped with a MicroLogic 2.0 control unit.
It is used for overload and short‑circuit protection in low‑voltage power distribution systems, widely applied in industrial plants, commercial buildings, and infrastructure projects.
| Model Segment | Description |
| C125N | ComPacT NS1250N series, frame size 1250A, breaking capacity 50kA@415VAC |
| 4 | 4‑pole configuration (4P) |
| 20 | MicroLogic 2.0 control unit (basic protection functions) |
| FM | Fixed mount, manual operation, front connection |
- Core Technical Specifications
| Item | Value | Notes |
| Model | Schneider Electric C125N420FM | Full description: ComPacT NS1250N 4P 1250A 50kA MIC2.0 |
| Frame current | 1250A | Maximum rated operational current |
| Poles | 4 poles (4P) | 3 phases + neutral protection |
| Trip unit | MicroLogic 2.0 | Long‑time (L), short‑time (S), instantaneous (I) protection |
| Rated current (Ir) | 1250A | Adjustable via trip unit |
| Ultimate breaking capacity (Icu) | 50kA@415VAC | Complies with IEC 60947‑2 |
| Mounting | Fixed, front connection | Suitable for standard switchgear |
| Operation | Manual | With mechanical indication and lockability |
| Rated insulation voltage (Ui) | 1000VAC | IEC 60947‑2 |
| Rated operational voltage (Ue) | 400/415VAC (50Hz) | Standard 3‑phase voltage |
| Short‑time withstand current (Icw/1s) | 50kA | Ensures system stability during faults |
| Protection degree | IP30 | Protection against solid foreign objects |
| Wiring capacity | Max. 300mm² copper | For high‑current loads |
- Features & Advantages
- Comprehensive protection
MicroLogic 2.0 provides 3‑stage protection (L‑S‑I) with adjustable settings.
Supports fault diagnostics and alarm output for easy maintenance.
- Efficient design
Green “T” design reduces panel wiring time by 40%.
Ergonomic operating handle for improved safety and comfort.
Modular structure supports accessories: auxiliary contacts, alarm contacts, undervoltage release, etc.
- Reliable performance
50kA high breaking capacity for fast fault interruption.
Mechanical life: up to 10,000 operations; electrical life: up to 5,000 operations.
Ambient temperature: −5°C to +40°C (full rating), −25°C to +70°C (derated).
- Installation & Applications
4.1 Installation Requirements
Suitable for standard distribution boards with industry‑standard mounting depth.
Front connection for easy wiring and maintenance.
Sufficient heat dissipation space required for stable long‑term operation.
4.2 Typical Applications
Incoming protection for main power distribution boards in industrial plants
Power distribution systems for large commercial complexes
UPS input/output protection in data centers
Critical load protection in infrastructure (hospitals, airports, metros)
Main protection for Motor Control Centers (MCC)
- Related Models & Alternatives
5.1 Derived models in the same series
| Model | Difference | Application |
| C125N320FM | 3 poles (3P) | 3‑phase loads without neutral protection |
| C125N450FM | MicroLogic 5.0 trip unit | Energy measurement and advanced protection |
| C125N420PM | Draw‑out installation | Easy maintenance without power interruption |
| C125N420RM | Plug‑in installation | Fast replacement for backup equipment |
5.2 Cross‑series alternatives
| Replacement | Series | Main difference | Price reference |
| NSX1250N 4P MIC2.0 | ComPacT NSX | New generation, breaking capacity 65kA | Approx. +10% |
| Masterpact MTZ12 | Masterpact MTZ | Air circuit breaker for higher power systems | Approx. +50% |
5.3 Competitive brand equivalents
| Brand | Replacement | Rating |
| Siemens | 3WL1212‑3CB36‑4GA4 | 1250A 4P 50kA basic protection |
| ABB | Tmax T6H1250 PR221DS‑LSI 4P | 1250A 4P 50kA LSI protection |
| Eaton | NZM4‑1250N 4P | 1250A 4P 50kA basic protection |
- Purchasing & Usage Tips
- Authentic procurement: Purchase via authorized Schneider Electric distributors or official channels to ensure quality and service.
- Accessories: Optional auxiliary contacts, alarm contacts, shunt trip, undervoltage release, etc.
- Parameter setting: MicroLogic 2.0 can be programmed; adjust according to load characteristics.
- Maintenance: Routine inspection every 1–2 years, including mechanism, terminals, and protection functions.
> Note: C125N420FM complies with IEC 60947‑2, GB 14048.2 and other international & national standards. It is fully compatible with Schneider Prisma E, Blokset and other panel systems.
- Selection & Replacement Guidelines
- Compatibility Rules
Industrial relay sockets follow international standard dimensions and are interchangeable across brands if:
Pin count matches relay pole number
Rated current (≥10A) meets load
Mounting (DIN-rail/screw) matches panel design
- Terminal Type Selection
Conventional screw: PTF08A / PTF11A / PTF14A-suitable for low-vibration environments
Finger protection: PTFZ series-suitable for areas with frequent access
Push-In Plus: PTF-PU series-ideal for mass wiring, high vibration resistance
- Discontinued Models
PTF08A-E / PTF14A-E are discontinued with limited stock.
Use PTFZ series as the preferred replacement.
> Note: PTF series sockets are rated 10A/250VAC, dielectric strength AC 2000V, operating temp −25 °C to +55 °C, suitable for 0.5–2.5 mm² copper wires.
