In electrical wiring and cable manufacturing, a 4G cable is a four-core cable where one of the conductors is a dedicated protective earth (ground) wire, universally identified by green/yellow insulation. When you are sourcing wire for a 3-phase motor, a commercial HVAC unit, or an industrial control panel, the 'G' in the part number dictates your earthing topology and fault-clearing capabilities. Confusing this designation with cellular '4G' networks or misinterpreting it as a generic '4-core' cable without a dedicated ground can lead to dangerous installations, failed inspections, or equipment damage.
Decoding the IEC Harmonized Cable Code
To understand what 4G means, you have to look at the CENELEC harmonized cable codes (widely adopted across Europe, the UK, and referenced globally in IEC standards). A typical part number looks like H07RN-F 4G2.5. Here is exactly how to read that string:
- H: Harmonized to European/IEC standards.
- 07: Voltage rating (450/750V RMS).
- R & N: Insulation and sheath materials (Ethylene Propylene Rubber insulation, Polychloroprene outer sheath).
- F: Flexible (Class 5 stranded copper).
- 4: Total number of conductors in the cable.
- G: Green/Yellow protective earth conductor is included.
- 2.5: Cross-sectional area of each core in square millimeters (mm²).
Worked Numeric Example: Sizing a 4G Cable for a 3-Phase Load
Let's look at what this changes in a real installation. You need to wire a 5.5 kW 3-phase induction motor (nominal 400V, power factor 0.85) located 45 meters from the distribution board. The motor requires a 4-core supply (3 phases + Earth) because it is a balanced load and does not require a neutral.
1. Calculate Full Load Current (FLC):
Using the 3-phase power formula: $I = \frac{P}{\sqrt{3} \times V \times PF}$
$I = \frac{5500}{1.732 \times 400 \times 0.85} \approx 9.35A$. We will design for 10A to allow a margin for startup inefficiencies.
2. Select the Cable:
A standard 4G2.5mm² PVC/SWA (Steel Wire Armoured) cable in conduit (Reference Method B) has an ampacity of roughly 18.5A. This easily handles the 10A load.
3. Verify Voltage Drop:
The voltage drop factor for 2.5mm² copper is approximately 15 mV/A/m.
$Drop = \frac{15 \times 10A \times 45m}{1000} = 6.75V$.
Percentage drop = $(6.75 / 400) \times 100 = 1.68\%$. This is well within the standard 5% maximum limit for non-lighting circuits.
The Installation Reality: Because you selected a 4G cable, the green/yellow core is terminated directly to the motor's chassis earth terminal and the panel's earth bar. If a phase-to-chassis fault occurs, the low-impedance path through the 'G' core ensures the 16A Type C breaker trips in under 0.4 seconds, clearing the fault safely. If you had mistakenly pulled a 4X cable, you would have no dedicated earth path, leaving the motor chassis energized at 230V-to-ground during a fault—a lethal hazard.
Where You Meet 4G Cables in Practice
You will primarily encounter 4G designations in commercial and industrial electrical work, specifically where 3-phase power is utilized without a neutral requirement:
- 3-Phase Motors: Lathes, CNC mills, large air compressors, and conveyor drives. These are star or delta wound and only need L1, L2, L3, and Earth.
- Delta-Wired Heating Banks: Industrial immersion heaters or duct heaters wired in a delta configuration do not use a neutral, making 4G the correct feeder.
- Commercial HVAC: Large rooftop chillers and AHU (Air Handling Unit) fans often utilize 4G feeds.
Common Confusions: 4G vs 4X, 4C, and Cellular IoT
When sourcing parts, the '4G' label is a frequent trap for the uninitiated. Here is how to avoid the most common mistakes:
| Term | What It Actually Means | The Danger / Confusion |
|---|---|---|
| 4G | 4 cores, including Green/Yellow Earth (IEC/CENELEC). | None, provided you need an earth core. |
| 4X | 4 cores, NO Green/Yellow Earth (IEC/CENELEC). | Ordering 4X for a motor feed leaves you without a dedicated ground wire. |
| 4C | Colloquial for '4-Conductor'. Not an official harmonized suffix. | Suppliers might send 4X, 4G, or even 4-core control cable. Always specify G or X. |
| Cellular 4G | 4th Generation LTE mobile networks. | Searching '4G wire' on Amazon/AliExpress often yields LTE antennas and IoT modem pigtails, not mains cable. |
Frequently Asked Questions
What is the exact difference between 4G and 4X cable?
The only physical difference is the color of the fourth core's insulation. In a 4G cable, one core is strictly extruded with green/yellow PVC or rubber to designate it as the protective earth. In a 4X cable, all four cores are standard phase colors (e.g., Brown, Black, Grey, and Blue). Electrically, the copper inside is identical, but the 'G' designation is a mandatory safety and code-compliance marker for grounding.
Can I use a 4G cable for a standard single-phase 240V circuit?
Yes, but it is usually overkill and wasteful. A standard single-phase circuit requires Line, Neutral, and Earth (3 cores). If you use a 4G cable (which has 3 phase colors + 1 earth), you would use Brown (Line), Blue (Neutral), and Green/Yellow (Earth). The remaining Black and Grey cores would simply be cut short and capped at both ends. For single-phase runs, a standard 3G (3-core with earth) cable like H05VV-F 3G1.5 is the correct and cost-effective choice.
Does the 'G' in 4G mean the cable is rated for direct ground burial?
No. The 'G' stands exclusively for the Green/Yellow earth conductor. It tells you absolutely nothing about the cable's outer jacket or its suitability for direct burial. If you need to bury a 4-core cable directly in the earth, you must look at the jacket material and construction—specifically, you need an SWA (Steel Wire Armoured) cable or a specialized direct-burial UF/USE rated cable, not just a standard flexible H07RN-F 4G rubber cable.
How do I identify the phase cores in a modern 4G harmonized cable?
Under modern IEC 60445 / BS 7671 harmonized color codes, a 4G cable (3-phase + Earth) will contain the following core colors: Brown (L1), Black (L2), Grey (L3), and Green/Yellow (Earth). If you are working on older legacy installations (pre-2006 in the UK/EU), you may encounter the old colors: Red (L1), Yellow (L2), Blue (L3), and Green (Earth). Always verify with a multimeter before terminating.
