Old vs new wiring colours: Why did they change and how to spot old wiring

The current system

The current wiring colours were introduced by the IEC in 2004, and fully came into effect in March 2006 under the British Standard BS 7671 wiring regulations.

These changes meant that all new wiring installations after March 2006 had to adopt the new colours, which are green/yellow, blue and brown in standard wiring, with black and grey being introduced in 3 phase wiring setups.

Green/yellow wires are indicative of the PE or Protective Earth wire, designed as a safety precaution to direct current into the ground to prevent electrocution.

Brown, grey and black wires are used as live wires, with black being used as line 2 of three phase wiring, and grey as line 3. As the name suggests, the live wire delivers live power from the electricity source to the appliance.

The blue wire completes the circuit as the neutral wire, responsible for regulating voltage within the setup.

Pre 1977 system

In this iteration of electrical wiring setups, earth wires were coloured green, neutral wires were black, and live wires were red. Three phase wiring consisted of red, yellow and blue wires for lines 1, 2, and 3 respectively.

Pre 2004 system

Following on from the 1977 system, the pre 2004 system had one slight change with the introduction of the green/yellow earth wire as opposed to the solid green used pre-1977.

Why were the colours changed?

The colours of wiring were changed mainly to match the European wiring regulations when the UK was still a part of the EU, in a process known as harmonisation. The change was made around 3 decades after most of Europe, as the IEE did not consider the change to the neutral and phase colours to be a safe choice at the time.

How to spot old wiring

Due to the fact that the post 2004 wiring colour changes only applied to new installations, there is a chance that your domestic or commercial property could be wired to the old standard.

You can find this out by inspecting your wiring, if your setup includes red and black wires, and your three phase wiring features red, blue, and yellow lines, this means your wiring is outdated.

Does old wiring need to be replaced?

While the old standard of wiring isn’t considered dangerous in itself, considering the length of time since the old standards have been used, it is highly recommended that a rewire is completed.

If you find during a wiring inspection that your PE wires are solid green as opposed to green/yellow, it should be treated as a high priority to replace this wiring, as the older the wiring setup is, the greater the risk for issues and faults, possibly even as severe as electrical fires.

The colours of standard and three phase wires have undergone numerous changes over the years, and keeping up to date with the regulations and knowing when wiring needs to be replaced is incredibly important. Here at ElectricalDirect, we offer anything you could need to create a new wiring installation, or upgrading an existing one, including cables and cable management solutions, as well as an expansive range of sockets, switches and other wiring products.