The official Chinese wire color code is governed by the GB 50303 building electrical standard and GB/T 5023 cable standard. For 3-phase AC power, China uses Yellow (L1), Green (L2), and Red (L3). For single-phase, Red or Brown is Line, Light Blue is Neutral, and Green/Yellow stripe is Protective Earth (PE). If you are troubleshooting imported Chinese machinery or wiring a panel with Chinese-sourced cables, you must treat Yellow, Green, and Red as energized phase conductors—not as ground or neutral, which is a fatal mistake when applying US NEC or modern IEC logic.

MAINS HAZARD: Chinese 3-phase Green (L2) carries full line voltage (typically 220V to neutral, 380V line-to-line). Never assume a solid green wire is a safety ground. Always de-energize, lock out the breaker, and verify dead with a tested multimeter before touching any conductor.

The Complete Chinese Wire Color Code Reference (GB Standards)

China's national standards (Guobiao or GB) align partially with IEC but retain legacy 3-phase colors that are deeply embedded in domestic manufacturing and construction. Below is the definitive reference for AC and DC wiring sourced from mainland China.

Function / Phase Chinese GB Standard Color Typical Application Context
3-Phase L1 (Phase A) Yellow Main busbars, 3-phase motor feeds, industrial panels
3-Phase L2 (Phase B) Green Main busbars, 3-phase motor feeds, industrial panels
3-Phase L3 (Phase C) Red Main busbars, 3-phase motor feeds, industrial panels
Single-Phase Line (Hot) Red or Brown Residential branch circuits, appliance internal wiring
Neutral (N) Light Blue (or Blue) Return path for AC circuits, mandatory for all N connections
Protective Earth (PE) Green/Yellow Stripe Equipment grounding, chassis bonding, panel ground bars
DC Positive (+) Brown (Legacy: Red) Solar arrays, battery banks, control circuit power
DC Negative (-) Blue (Legacy: Black) Solar arrays, battery banks, control circuit return

Regional Clashes: China GB vs. IEC vs. US NEC

When integrating Chinese-manufactured equipment (like CNC machines, solar inverters, or industrial battery racks) into a Western facility, the color code mismatch is the primary source of wiring faults. The table below maps the exact conflicts.

Conductor China (GB 50303) International (IEC 60446) United States (NEC / NFPA 70)
3-Phase L1 Yellow Brown Black (or Brown)
3-Phase L2 Green Black Red (or Orange for high-leg)
3-Phase L3 Red Grey Blue (or Yellow)
Neutral Light Blue Blue White or Grey
Ground (PE) Green/Yellow Green/Yellow Green, Green/Yellow, or Bare

The Critical Takeaway: Under NFPA 70 (NEC), green is strictly reserved for equipment grounding. Under Chinese GB standards, solid green is an energized 3-phase conductor (L2). If you wire a Chinese machine into a US panel and connect the machine's solid green wire to your ground bar, you will immediately create a dead short or energize the machine's chassis upon startup.

The Rows People Get Wrong (And How They Cause Faults)

In the field, theoretical standards meet the reality of cheap manufacturing, UV fading, and mixed supply chains. Here are the specific rows from the reference table that cause the most bench and jobsite failures.

1. Solid Green (L2) vs. Green/Yellow Stripe (PE)

The Error: Treating a faded Green/Yellow ground wire as a solid Green phase wire, or vice versa. The Reality: On low-cost Chinese cables, the yellow stripe on the PE wire is often printed poorly or fades under UV/heat exposure, making it look solid green. If you terminate this into a 3-phase contactor instead of the ground bar, the machine chassis becomes live. Conversely, if you terminate a true L2 (solid green) into the PE bar, you trip the main breaker or cause a ground fault.

2. Black Wire in Control Circuits

The Error: Assuming black is always an AC 'Hot' wire (US NEC logic). The Reality: In Chinese control panels and DC systems, black is frequently used as the DC Negative return, a switched AC leg, or a low-voltage signal wire. Always trace black wires to their terminal block labels (e.g., '0V', 'COM', or 'N') before applying power.

3. Single-Phase Red vs. Brown

The Error: Mixing up single-phase line colors in mixed-origin panels. The Reality: Modern Chinese export cables use Brown for single-phase Line to comply with IEC harmonization standards. However, domestic Chinese building wiring and internal appliance wiring still heavily favor Red. If you see both Red and Brown in the same enclosure, verify which one is actually carrying the switched load.

Decision Path: Identifying Unmarked or Mixed-Origin Wires

When you open a control cabinet and the wire colors don't match the terminal labels, or the panel contains a mix of Chinese, European, and US components, use this decision tree to safely identify and terminate the conductors.

Condition / Observation Immediate Action Final Termination / Tool Pick
Wire is Solid Green Test for voltage to known ground. Do NOT assume it is PE. If hot: Treat as L2. If dead: Verify continuity. Mark with 3M Scotchlok Red Heat Shrink to re-identify as Phase.
Wire is Green/Yellow but stripe is faded Perform continuity test to the metal chassis/ground bar. If < 1 ohm: Terminate to PE bar. Wrap with Green/Yellow electrical tape at both ends to restore code compliance.
Wire is Black (unknown origin) Check terminal labels for '0V', 'COM', or 'L'. Use a Klein Tools NCVT-2 non-contact tester. If it beeps, treat as AC Hot. If silent, measure DC voltage to ground.
Wire colors completely mismatch panel labels Stop. Do not trust the insulation color. Trace point-to-point with a multimeter. Re-label all wires using a Brother PT-D210 label maker with wrap-around flags.

Safe Interpretation When Markings Are Missing

If you are dealing with a bundle of Chinese-sourced wires where the insulation is degraded, unmarked, or entirely the wrong color (e.g., a manufacturer used all black wire to save costs), you must abandon color-code reliance entirely and rely on electrical measurement.

Bench Tip: Never use a 'wiggy' or solenoid voltage tester on modern Chinese switch-mode power supplies or VFDs (Variable Frequency Drives). The high-impedance inputs can give false readings or be damaged by the tester's low impedance. Always use a CAT III or CAT IV digital multimeter (DMM) with a low-impedance (LoZ) mode to bleed off phantom voltages.

Step-by-Step Verification Protocol:

  1. Visual Trace: Physically trace the wire from the component back to the terminal block. Look for printed numbers on the wire jacket (e.g., 'L', 'N', 'PE', or numbers like '101', '102' which denote control lines).
  2. De-Energize and Test Continuity: With the breaker OFF and locked out, use your DMM's continuity setting. Check the suspect wire against the known ground bus. A reading of < 0.5 ohms confirms it is a Protective Earth (PE) conductor, regardless of its color.
  3. Energize and Test Voltage: If continuity to ground is open, restore power safely. Measure AC voltage from the suspect wire to a known ground.
    • If you read ~220V (or ~120V depending on local step-down transformers), it is a Line/Hot conductor.
    • If you read 0V to ground, but ~220V to a known Hot wire, it is likely a Neutral or a switched return leg.
  4. Re-Identify: Once identified, you must permanently re-mark the wire at both termination points. Slip a piece of correctly colored heat shrink (Brown for Hot, Blue for Neutral, Green/Yellow for Ground) over the wire and apply heat. This ensures the next technician does not repeat your troubleshooting process.