Wire and Cable Marking Guide – Symbols, Codes, and Applications
Electrical wires and cables come with alphanumeric markings that indicate material, insulation, number of conductors, and safety ratings. Understanding these markings is crucial for safe installation, compliance with electrical codes, and choosing the right cable for the job.
1. What Do Wire and Cable Markings Mean?
Every electrical wire or cable has a printed marking or embossed code that provides essential information, including:
- Conductor Material – Copper (Cu) or Aluminum (Al).
- Insulation Type – PVC, rubber, polyethylene.
- Number of Conductors – How many wires are inside.
- Wire Gauge (AWG/mm²) – Determines current capacity.
- Flame Resistance & Safety Ratings – Fire-retardant, low-smoke, or UV-resistant.
Understanding these markings and codes ensures correct usage, preventing electrical hazards and code violations.
2. Wire Marking System – Letter Codes
Electrical wires and cables are labeled using letter codes, which describe the conductor, insulation, and special properties.
2.1 Conductor Material Identification
The first letter in a cable marking often refers to the type of conductor:
- "A" – Aluminum (e.g., AВВГ for aluminum cables).
- No "A" – Copper (default conductor material for electrical wiring).
2.2 Insulation and Sheathing Codes
The next set of letters defines insulation and sheathing type:
| Letter Code | Meaning | Example |
|---|---|---|
| V | PVC insulation | VVG – PVC-insulated cable |
| P | Polyethylene insulation | APV – Aluminum wire with polyethylene insulation |
| R | Rubber insulation | PR – Rubber-insulated wire |
| G | Flexible cable | VVG-G – Flexible PVC cable |
| K | Shielded cable | VK – Shielded conductor |
| B | Armored cable | VBBShv – PVC-insulated, armored with steel tape |
For fire-resistant cables, additional labels may be included:
| Code | Property | Example |
|---|---|---|
| FRLS | Fire-resistant, low smoke | VVG-FRLS |
| HF | Halogen-free (low toxicity) | NYM-HF |
| NG (A) | Non-flammable, class A | VVGng(A) |
3. Understanding Numerical Wire Markings
Wire markings also include numbers that define:
3.1 Wire Gauge and Conductors
Wires are labeled with their gauge (AWG) or cross-sectional area (mm²), followed by the number of conductors.
Example:
- 3×2.5 – Three-conductor cable, each wire 2.5 mm² in cross-section.
- 2×4 – Two-conductor cable, each 4 mm² thick.
Larger numbers indicate thicker wires, capable of carrying more current.
3.2 Voltage Rating
Some cables include voltage rating in kilovolts (kV), indicating maximum safe operating voltage.
| Marking | Voltage Rating |
|---|---|
| 1 | Up to 1 kV |
| 6 | Up to 6 kV |
| 10 | Up to 10 kV |
4. Specialized Wire Markings
Some cables are labeled for special applications, such as:
4.1 Power Cables (Heavy-Duty Applications)
Power cables often include markings for:
| Symbol | Meaning |
|---|---|
| B | Armored (Steel Tape) |
| Sh | Protective Sheath |
| NYY | Heavy-duty outdoor use |
Example:
VBBShv – Armored cable with steel tape and PVC sheath.
4.2 Control Cables (Low-Voltage Signaling & Automation)
Control cables use "K" to denote signaling applications.
| Example | Description |
|---|---|
| KSPV 4×0.5 | Control cable, 4 conductors, 0.5 mm diameter each |
These cables are used in industrial automation, security systems, and data transmission.
4.3 Fire-Resistant & Safety-Rated Cables
Safety cables have additional fire-resistant and non-toxic labeling.
| Marking | Meaning |
|---|---|
| FRLS | Fire-resistant, low smoke |
| HF | Halogen-free (low toxicity) |
| NG(A) | Non-flammable, Class A |
These cables are used in hospitals, schools, commercial buildings, and areas with high fire safety standards.
5. Color Coding for Electrical Wires
Beyond alphanumeric markings, color coding helps identify wires quickly and safely.
5.1 Standard Wire Color Code
| Function | Color |
|---|---|
| Live/Phase | Black, Brown, Red |
| Neutral | Blue |
| Ground (Earth) | Green-Yellow |
Using incorrect color codes can lead to serious electrical hazards.
5.2 Color Coding in Control & Signal Cables
- Striped wires indicate signal conductors.
- Solid colors are used for primary power distribution.
6. NEC and International Wire Standards
Electrical cable markings must comply with national and international standards to ensure safety and performance.
6.1 National Electrical Code (NEC) – USA
The NEC defines wire ampacity, voltage ratings, and safety codes.
- THHN – Heat-resistant, used in conduit.
- UF – Underground feeder cable.
- NM-B (Romex) – Indoor residential wiring.
6.2 IEC (International Electrotechnical Commission)
The IEC standardizes color codes and cable classifications across Europe and other regions.
- NYM – General-purpose wiring.
- H07RN-F – Rubber-insulated flexible cable for industrial use.
6.3 Fire Safety & Environmental Compliance
- Low Smoke Zero Halogen (LSZH) – Non-toxic emissions during fire.
- CPR (Construction Products Regulation, EU) – Fire-resistant construction cables.
7. Choosing the Right Wire for Your Application
Checklist for Selecting Electrical Wire:
✔ Check voltage and current requirements
✔ Confirm insulation type and fire rating
✔ Use proper color coding for safety
✔ Verify compliance with NEC or IEC standards
✔ Consider environmental factors (outdoor, underground, industrial use)
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If you’re unsure about wire selection or compliance, consult a licensed electrician to ensure safe and code-compliant installations.