Color codes of electrical wires : correspondence and nomenclature

Who has never got lost in the colors of electric wires? With the evolution of electrical standards, each generating new colors, there is plenty! What are the colors for, how to identify the role of each thread? Once you know how to decipher the color code, it’s ultimately not that complicated. Follow the guide, the safety of your electrical installation depends on it. And yours.

The reference standard NF C 15-100 imposes its code.

Since 1970, it has been the reference standard for all electrical installations. In the new or in renovation, it is the NF C 15-100 which takes precedence. Any intervention must be carried out in compliance with this electrical standard designed to improve the safety of homes and their occupants.

Keep in mind that a single-phase (low voltage) electrical circuit is always made up of three wires: phase, neutral and earth. Each has a specific function and color code. Between phase and earth, or between neutral and phase, the voltage is 220 volts. It is zero between neutral and earth.

It was therefore in 1970 that the current color code was introduced. Its objective: to rationalize the identification of cables. The new nomenclature simplifies the understanding of the role of each wire, so as to secure the installation. But what are the colors indicated by the reference standard? And what wire do they correspond to?

Red, brown or black: the phase

The phase conductor is the cable that supplies the house with electricity. Thanks to him, energy circulates everywhere. Usually red, it also comes in black or brown. But the color of the sheath is always plain.

Blue: neutral

The neutral conductor has a specific function. This cable measures power consumption. If necessary, it is he who trips the circuit breaker. It cuts the current, or restarts it. The neutral cable has a protective role: by making sure to stop the current in the event of an overvoltage, it protects you from any electrocution. Its sheath is a more or less light blue.

Yellow and green: the ground wire

With its two-tone dress, the third yarn is the prettiest. Attention: no wire only yellow, or solid green; it’s forbidden. The ground wire is striped yellow and green. This cable does not conduct electricity. It plays a protective role by redirecting abnormal current losses to the earth connection, buried in the basement. This can happen when an electrical device is poorly insulated or faulty. By thus ensuring the safety of the installation, the ground wire protects you against any risk of electrification, or even electrocution. It became mandatory in 1970.

Orange or purple: the shuttle

It is possible that one or the other of these two colors (or both) is missing from your installation. This is not abnormal, since their presence is not mandatory, unlike the previous three. Purple and orange indicate “shuttle wires”, used to connect two switches or when installing a two-way switch. The shuttle cable is placed just after the receiver. Purple signals a back and forth, while orange is in the return of a push button. But the color of the shuttles is not regulated as strictly as that of the three obligatory wires (phase, neutral and ground).

Please note: the code has changed!

If your electrical installation is old, that is to say if it dates from before 1970, the colors are different. As long as it has known some not very scrupulous interventions, and here you are in front of a pretty firework of colors!

Green or yellow: the phase

This is why solid green or yellow cables are now prohibited! Until 1969, the phase conductor was identified in yellow or green. No need to add confusion.

Gray or white: neutral

Before switching to blue, the neutral cable was colored… neutral. But it still has the same function: measure consumption, cut or restart the current.

Red or black: the ground wire

Before 1970, this cable was not always present in installations, as it was not yet compulsory. The absence of a ground wire is also an indication of dilapidation. Make no mistake when you come across a red wire… Phase or earth? To be sure, it is better to test it. We explain how a little later.

To tell the truth, the standard of the time was less strict and these colors are not an absolute reference. The test is essential as soon as you have to carry out renovation work in an old house. You could even discover wires sheathed in fabric, which was practiced well before 1969. If this is the case, do not hesitate to bring everything up to current standards: NF C 15-100!

The three-phase circuit has its own code

Some homes are equipped with a three-phase installation, which therefore includes…? Three phases, well done! In this type of circuit, electricity flows with a voltage of 380 volts. The diameter of the cables is larger (it goes up to 16 mm2), which allows it to withstand higher voltage and higher amperage. The three phase wires are differentiated according to a precise nomenclature.

  • Marron for the phase n° 1.
  • Noir for the phase n° 2.
  • Gris for the phase n° 3.
  • Bleu : neutralas in the classic single-phase installation.
  • green and yellow : Earth. Again, no difference with the low voltage circuit.

I’m colorblind, colors confuse me!

If you are lost between the colors, or simply have doubts about your installation – fearing that the color code is a little whimsical – there is a solution. You can test the cables to better identify them. To do this, take a tester screwdriver or a multimeter. The screwdriver tester is used to identify the flow of current. As for the multimeter, it measures the intensity and the voltage of the electric current. By testing the electrical flow between the different wires, you can determine the role of each and especially identify the phase.

With a luminous screwdriver, the phase lights up

When its tip is placed on a bare phase wire, the tip of the screwdriver lights up. Like Frodo’s sword when an Orc approaches… Be sure to put on gloves and be careful during this test: you have to touch part of a bare electric wire (without its sheath)! Be careful that nothing metallic comes into contact with the rod of the screwdriver, it is dangerous. In any case, you are sure to identify the phase for sure.

With a multimeter, locate the flow of current

First and foremost, ground yourself. This device has two tips. To use it, do the following: dip a spike into the earth (directly into the ground), and test the cables one by one. The tips touch the base of the cable, thus locating the current. When the device does not detect any voltage, it is because it is a neutral wire or a ground wire. When it reports a measurement (between 220 and 230 volts), you have found the phase. Between neutral and earth: no voltage. It only appears between phase and neutral, and between phase and earth.

Safety first!

  • Once you have located the phase wire, do not begin any work on your electrical installation until you have cut the power at the level of the general table.
  • The switchboard is also mandatory equipment. Its circuit breaker allows you to cut off the power supply to work in complete safety. No more old pre-fuses! From now on, your panel must include differential circuit breakers.
  • If your installation is not connected to Earth, install it without delay! It is a mandatory and indispensable protection. Hundreds of fire outbreaks and accidents are avoided each year thanks to earth.
  • Make sure that each electrical cable passes through the GTL, the Housing Technical Sheath. Be careful that no humidity, no stagnant liquid is there. The cables must be properly sheathed or protected by rods. At the slightest damaged cable, do not connect anything.
  • When working on an electrical installation, equip yourself Consequently. Opt for crepe or rubber soles (non-conductive) and tools with insulated handles.
  • Do not make any electrical installation in the immediate vicinity of a point waterespecially the shower or the bathtub.
  • Find out about the instructions and obligations related to the standards NF C 15-100, it’s very instructive!

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