Explore our top-tier DIN-rail compatible miniature circuit breakers, RCCBs, and RCBOs engineered for global OEM/ODM applications.
In modern industrial automation, low-voltage power distribution, and commercial electrical installation, precise dimensional standardized mounting is critical for enclosure panel design, thermal management, and circuit protection integrity. The term Miniature Circuit Breaker (MCB) sizes refers not merely to external physical housing metrics, but to an internationally standardized mechanical topology governed by IEC 60898-1, IEC 60947-2, and DIN 43880 specifications.
Originating from Yueqing, Wenzhou—the world's dominant hub for electrical equipment manufacturing—Wenzhou OFA Electrical Technology Co., Ltd. (operating under the global proprietary brand OFA) has established engineering benchmarks for precision dimensional manufacturing, arc-extinction chamber geometry, and terminal clamp specifications. This technical guide outlines the precise physical dimensional matrices, thermal-magnetic breaking characteristics, and international procurement standards required by electrical engineers, EPC contractors, and OEM panel builders worldwide.
Miniature Circuit Breakers engineered by tier-1 China manufacturers like OFA adhere to strict spatial footprints. The standard width per pole is exactly 17.5mm to 18mm, with a uniform front cut-out height of 45mm and a overall depth ranging between 68mm and 75mm (excluding operating handle clearance).
| Pole Configuration | Modular Width (mm) | Physical Height (mm) | Depth (Overall / Built-in) | Nominal Current Range (In) | Rated Breaking Capacity (Icn) |
|---|---|---|---|---|---|
| 1P (Single Pole) | 17.5 mm – 18.0 mm | 81.0 mm – 85.0 mm | 68.0 mm / 44.0 mm cutout | 1A – 63A (Up to 125A in Frame B) | 4.5kA / 6.0kA / 10.0kA |
| 1P + N (Compact RCBO/MCB) | 18.0 mm (1 Module Width) | 85.0 mm – 90.0 mm | 70.0 mm / 44.0 mm cutout | 6A – 40A | 6.0kA / 10.0kA |
| 2P (Double Pole) | 35.0 mm – 36.0 mm | 81.0 mm – 85.0 mm | 68.0 mm / 44.0 mm cutout | 1A – 125A | 6.0kA / 10.0kA / 15.0kA |
| 3P (Triple Pole - 3 Phase) | 52.5 mm – 54.0 mm | 81.0 mm – 85.0 mm | 68.0 mm / 44.0 mm cutout | 1A – 125A | 6.0kA / 10.0kA / 15.0kA |
| 4P (Four Pole - 3P+N) | 70.0 mm – 72.0 mm | 81.0 mm – 85.0 mm | 68.0 mm / 44.0 mm cutout | 1A – 125A | 6.0kA / 10.0kA / 15.0kA |
Selecting the appropriate miniature circuit breaker physical dimension and electrical frame size requires evaluating operational thermal environments, trip curves, and terminal cable gauge compatibility.
When multiple MCBs are installed side-by-side in high-density commercial distribution boards, internal temperature rise lowers the effective thermal trip current. Sizing guidelines dictate applying a diversity factor (0.8 to 0.9) or incorporating 0.5-module ventilation spacers between high-load breakers to prevent premature nuisance tripping.
MCB sizing involves matching the instantaneous electromagnetic trip curve to the load dynamic. B-Curve (3-5 In) for resistive heating; C-Curve (5-10 In) for general lighting and commercial loads; D-Curve (10-20 In) for high inrush inductive motors and transformer primary protection.
Standard MCB sizes must accommodate copper/aluminum conductor cross-sections up to 25mm² or 35mm² for larger frame sizes (80A-125A). OFA breakers feature dual-purpose terminal tunnel clamps supporting both pin-type and fork-type copper busbars for streamlined panel assembly.
Founded in 2013 and headquartered in Yueqing, Wenzhou—the undisputed center of China's low-voltage electrical industry cluster—Wenzhou OFA Electrical Technology Co., Ltd. has grown into a premier specialized supplier of distribution switchgear, control equipment, and miniature circuit protection devices.
Operating under the proprietary independent brand "OFA", the company maintains continuous investments in dynamic R&D, automated stamping, silver-alloy contact spot-welding, and automated mechanical calibration. Recognized for unyielding integrity, OFA has earned the official Tax Credit Grade A rating for seven consecutive years, cementing long-term strategic supply agreements with global distributors, panel builders, and EPC project managers across Europe, South America, the Middle East, and Southeast Asia.
From high-voltage solar PV strings to sensitive cloud data center servers, OFA provides tailored miniature circuit breaker sizing configurations to handle diverse electrical demands.
Photovoltaic installations operate under sustained direct current (DC) stresses. OFA’s specialized DC MCB series (e.g., OFID and OFDZ47-DC) feature polarity-sensitive or non-polarized arc quenching magnets housed in standard 18mm/pole module widths, capable of interrupting DC voltages up to 1000V DC safely.
Modern mission-critical IT infrastructure requires selective tripping coordination to prevent widespread power outages. Compact RCBOs combining overcurrent and Class A/B leakage protection within a 1P+N (18mm) envelope ensure continuous uptime for uninterruptible power supplies (UPS).
Vibration resistance, terminal clamping reliability, and compact DIN-rail mounting are mandatory for industrial control panels (CPs). OFA's high-breaking capacity 10kA MCBs provide reliable short-circuit clearing in harsh ambient environments up to 70°C.
The global low-voltage circuit protection market is undergoing a paradigm shift from passive thermal-magnetic tripping mechanism towards active digital telemetry and solid-state power electronic switching. OFA's engineering laboratory is pioneering key innovations expected to define the next decade of low-voltage switchgear:
Integrating wireless communication protocols (RS485 Modbus, Zigbee, Wi-Fi) directly inside standard 18mm DIN-rail footprints allows real-time current, voltage, temperature, and power consumption metering without requiring external power transducers.
Combining AFDD microprocessors with traditional MCB thermal protection in compact 2-module sizes dramatically reduces fire hazards caused by carbonized cable degradation and loose terminal joints in compliance with IEC 62606.
Transitioning to 100% recyclable, halogen-free, high-temperature flame-retardant polyamide (PA66-V0) materials reduces carbon footprints during manufacture while maintaining self-extinguishing safety ratings under severe short-circuit arc flash testing.
Developing ultra-fast semiconductor switching elements capable of breaking short-circuit faults in microseconds, virtually eliminating mechanical contact erosion and extending breaker operational life past 100,000 operations.
Every miniature circuit breaker produced by Wenzhou OFA Electrical Technology Co., Ltd. undergoes multi-stage rigorous laboratory type testing and 100% routine factory testing.
| Standard / Certification | Scope & Governance | Key Test Criteria Met | Target Regional Markets |
|---|---|---|---|
| IEC / EN 60898-1 | Low-voltage circuit breakers for household & similar installations | Thermal trip dynamic, short-circuit breaking (Icn), dielectric strength, mechanical endurance | European Union, UK, Asia, South America, Africa |
| IEC / EN 60947-2 | Low-voltage switchgear for industrial applications | Ultimate short-circuit capacity (Icu), service capacity (Ics), temperature rise limits | Global Industrial EPC Projects, Heavy Industry |
| CE Marking & RoHS | EU Health, Safety, and Environmental protection directives | Electromagnetic Compatibility (EMC), restriction of hazardous substances (lead, cadmium) | European Economic Area (EEA) |
| ISO 9001:2015 | Quality Management System | Full-process traceability from raw copper/silver inspection to automated calibration | Global Manufacturing Guarantee |
As a seasoned China Miniature Circuit Breaker supplier, Wenzhou OFA Electrical Technology Co., Ltd. provides comprehensive white-label OEM manufacturing and technical co-development services for international low-voltage brands and regional electrical distributors.
Get immediate expert answers to fundamental technical questions regarding MCB physical sizing, selection criteria, and China factory procurement.
A standard 1-Pole MCB built to DIN 43880 standards has a modular width of 17.5mm to 18mm, a front cutout panel height of 45mm, an overall height of approximately 81mm to 85mm, and a depth of 68mm to 75mm. This standard profile ensures seamless snap-on mounting on 35mm top-hat DIN Rails (EN 50022).
While standard MCBs rated up to 63A maintain the 18mm module width per pole, heavy-duty high-current MCBs (80A, 100A, 125A) utilize a larger frame size. These high-current breakers typically feature an expanded width per pole of 27mm (1.5 modules) to accommodate larger arc chute grids, thicker internal bimetals, and heavier wire terminal lugs up to 50mm².
A compact 1P+N breaker fits both the live pole and neutral switched pole into a single 18mm module width, whereas a standard 2P breaker occupies two modules (36mm). A 2P breaker contains independent thermal-magnetic trip units in both poles, whereas a 1P+N breaker provides thermal-magnetic protection on the live pole only while simultaneously isolating the neutral line.
Wenzhou OFA Electrical Technology Co., Ltd. combines over a decade of dedicated low-voltage R&D with Yueqing's robust supply chain advantage. OFA offers factory-direct pricing, 100% full quality control inspection SOPs, international standard certifications (CE, IEC), 7 consecutive years of Tax Credit Grade A credibility, and flexible OEM/ODM customization capabilities.
MCB thermal trip calibration is typically standardized at 30°C ambient temperature. When breakers are installed in compact enclosures or high ambient regions (e.g., solar combiner boxes exposed to sunlight), thermal derating must be calculated. For ambient temperatures exceeding 50°C, the nominal current capacity (In) can decrease by 10% to 15%, requiring proper panel ventilation or upsizing the breaker rating.
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