Function & Color Code Explained

A 4‑core power cable is a multi-conductor cable that contains four insulated conductors in one sheath. These cables are commonly used in three‑phase systems, although—with proper termination—they can also be adapted for single‑phase applications. The four cores typically follow an international color code which, in modern installations, is:

• Brown – Phase 1 (L1)
• Black – Phase 2 (L2)
• Grey – Phase 3 (L3)
• Blue – Neutral (N)

In three‑phase systems, each colored conductor (brown, black, and grey) serves as a distinct phase, while the blue conductor serves as the neutral return path. In many regions, these color conventions are in line with IEC standards. In older wiring systems (such as the old UK system), the colors might differ (e.g., red, yellow, blue, and green/yellow for earth), but the modern IEC standard is increasingly adopted worldwide.

How to Connect a 4‑Core Power Cable

Step-by-Step Guide

1. Identify the Function of Each Conductor:
   • Brown (L1): Connect to the first live phase terminal.
   • Black (L2): Connect to the second live phase terminal.
   • Grey (L3): Connect to the third live phase terminal.
   • Blue (Neutral): Connect to the neutral terminal.
2. Strip and Prepare the Wires:
   • Remove the outer sheath carefully.
   • Strip the insulation from the ends of each conductor according to manufacturer guidelines.
3. Terminate the Conductors:
   • Use appropriate connectors or terminal blocks designed for the cable’s cross-sectional area.
   • Ensure that connections are tight and secure to maintain electrical integrity.
4. Ensure Proper Grounding (if applicable):
   • If the installation requires an earth conductor and your cable does not include a dedicated earth, an external earth wire must be run alongside.
5. Verify Polarity and Phase Sequence:
   • In three‑phase systems, use a phase rotation tester to confirm the correct sequence.

Frequently Asked Questions

What is the black wire in a 4‑core cable?

Answer:
In a 4‑core cable (following the IEC color code), the black wire typically represents Phase 2 (L2). This conductor is one of the three live wires in a three‑phase installation and carries one of the three alternating currents.
Reference: IEC and industry forums (e.g., Electrical Installation Guide).

What is the grey wire in a 4‑core cable?

Answer:
The grey wire in a 4‑core cable is used as Phase 3 (L3). Like the brown and black wires, it is one of the live phases in a three‑phase system and carries its respective current.
Reference: IEC and technical publications.

Can you use a 4‑core cable for single‑phase applications?

Answer:
Yes, you can use a 4‑core cable for single‑phase systems—but it is not the most economical choice. In a single‑phase setup, only two conductors are required (one for the live and one for the neutral). The remaining conductors should be safely terminated (capped off) or repurposed according to local regulations. In some cases, installers may use the extra cores for future expansion or as an additional safety measure.
Reference: Discussions on professional electrician forums and guidelines from Mike Holt Enterprises.

Comparison Table: 4‑Core Cable Color Code & Applications

Conclusion

A 4‑core power cable is versatile and commonly used in three‑phase electrical installations, following the IEC color code of brown (L1), black (L2), grey (L3), and blue (neutral). While primarily designed for three‑phase systems, it can also be adapted for single‑phase applications if the unused conductors are properly terminated. Always follow local codes and manufacturer guidelines when connecting and installing power cables.

For further details, you can visit:

• IEC Official Website
• Mike Holt Enterprises
• Electrical Installation Guide