IEC 60446 / ČSN, old DIN, and US NEC — AC mains, DC, automotive, and data
| Function | IEC 60446 / ČSN (current) | Old ČSN / DIN (pre-2004) | US NEC | Notes |
|---|
Valid in EU since 2004. Czech installations must follow this standard. Key change: old black phase → brown/black/grey for L1/L2/L3. Green-yellow for PE has been mandatory throughout.
Still encountered in older Czech and German installations. Phase was often black or red, neutral light blue. Do not mix old and new color coding in the same installation — always label and verify with a tester.
Standard for North America. Hot = Black (or Red for second phase), Neutral = White/Grey, Ground = Green or bare. 3-phase uses Black/Red/Blue for phases L1/L2/L3.
Never assume wire function from color alone. Always verify with a multimeter or voltage tester, especially in older installations or when working with unknown wiring. Incorrect assumptions can be fatal.