Understanding the 3-phase wire color code is essential for safe and correct wiring in electrical installations. This guide explains the color codes used in different regions, including the U.S., UK, and international standards, along with common applications and safety tips.
three phase wire color code
What Is 3-Phase Wiring?
Three-phase wiring is a type of AC power used in industrial, commercial, and large residential applications. It delivers power through three separate conductors (phases), each 120° out of phase with the others. This system offers:
Consistent power delivery
Greater efficiency
Reduced electrical loss
Why Wire Color Codes Matter
Wire color coding:
Enhances safety
Prevents wiring errors
Aids in troubleshooting
Ensures code compliance
3 phase wire color code
U.S. 3-Phase Wire Color Code (Based on NEC)
For 208V/120V (Wye Configuration)
| Function | Wire Color |
|---|---|
| Phase A | Black |
| Phase B | Red |
| Phase C | Blue |
| Neutral | White |
| Ground | Green or bare |
For 480V/277V (Wye Configuration)
| Function | Wire Color |
|---|---|
| Phase A | Brown |
| Phase B | Orange |
| Phase C | Yellow |
| Neutral | Gray |
| Ground | Green or bare |
🔧 Tip: Orange is commonly used to indicate a 'high-leg' in delta systems.
UK 3-Phase Wire Color Code (IEC Standard)
In the UK and much of Europe, color codes follow IEC 60446 (harmonized standard):
| Function | Wire Color |
|---|---|
| Phase L1 | Brown |
| Phase L2 | Black |
| Phase L3 | Gray |
| Neutral | Blue |
| Ground (Earth) | Green/Yellow |
International IEC 3-Phase Color Code
IEC color coding is commonly used in many countries across Europe, Asia, and Africa.
| Function | Wire Color |
|---|---|
| Phase L1 | Brown |
| Phase L2 | Black |
| Phase L3 | Gray |
| Neutral | Blue |
| Ground | Green/Yellow |
Older UK Color Codes (Pre-2004)
| Function | Wire Color |
|---|---|
| Phase L1 | Red |
| Phase L2 | Yellow |
| Phase L3 | Blue |
| Neutral | Black |
| Ground | Green |
⚠️ Important: Older buildings may still use this scheme. Always check during repairs or retrofits.
3-Phase Color Code Comparison Table
| Region | L1 | L2 | L3 | Neutral | Ground |
|---|---|---|---|---|---|
| USA (120/208V) | Black | Red | Blue | White | Green or bare |
| USA (277/480V) | Brown | Orange | Yellow | Gray | Green or bare |
| UK/IEC | Brown | Black | Gray | Blue | Green/Yellow |
| UK (Old) | Red | Yellow | Blue | Black | Green |
Common Applications of 3-Phase Wiring
Industrial motors and machines
Large commercial HVAC systems
High-powered lighting systems
Elevators and lifts
Data centers and server rooms
Safety Tips for Working with 3-Phase Systems
Always turn off power before starting work.
Use a voltage tester to verify.
Label wires during installation or servicing.
Follow local electrical codes (NEC, IEC, etc.).
When in doubt, consult a licensed electrician.
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Conclusion
Understanding the 3-phase wire color code is essential for anyone dealing with electrical systems. Whether you're following NEC standards in the U.S. or IEC standards internationally, knowing the right color codes helps ensure safety, code compliance, and reliable operation.
For more technical wiring guides, diagrams, or to purchase 3-phase cable products, feel free to contact us today.
