Necessity and Standards of Electrical Wiring Color Codes

Why are Electrical Wiring Color Codes Important

Before starting any wiring project, it is possible to identify the purposes of the different house electrical wiring if you understand the diverse electrical wire colors and their code. Electrical wiring color codes matter a lot even if there are safety features such as the fuse, the double insulation design and the earth wire in plugs and appliances for electrical connection.

For example, in a home electrical system, there are usually three wires/lines in a power cord or in the whole power link entering into buildings. One wire brings electricity to the appliance and one wire completes the circuit by taking electricity away from the appliance, these two wires are called “live” and “neutral/zero” respectively. The third wire is the earth wire designed for important safety considerations.

Nema 23 red green yellow blue wire. The electrical wiring color code standards not only help in appliance addition, but also offer support when there is a need to replace the old wires with new ones.  Knowing the purpose of each wire will keep you safe and your house's electrical system in top working order.

What is Electrical Wiring Color Code Standard

It is important to abide by the electrical wiring color code standards for safety concerns. Electrical wiring color code standards are specified according to different power distribution branch circuits:

Alternating Current(AC):

AC is widely used in distribution and transmission electrical networks. In the low-voltage (the normal voltages of 240V and 415V delivered to most customers) distribution network, the transmission line generally adopts a three-phase four-wire system, of which three lines represent the three phases of L1, L2, and L3 respectively, and the other is a neutral line N.

Phase 1 Phase 2 Phase 3 Neutral Ground
Homes and offices:120, 208 or 240 Volts Black wire Red wire Blue wire White wire Green, Green with a Yellow Stripe, or Bare Wire
Industrial equipment: 277 or 480 Volts Brown wire Orange wire Yellow wire Gray wire Ground – Green, green with yellow stripe, or bare wire

Direct Current (DC):

DC distribution is limited to use in situations such as tramway and traction systems with a voltage of usually 600V, railway DC traction systems with a voltage of 1.5 kV between rail and overhead collector wire, lifts, printing presses and various machines where smooth speed control is desirable, electroplating or is simply used for battery charging. Usually, DC systems are of 2-wire or 3-wire types, of which a DC power has two terminals, one positive (+) and the other negative (-). The current flows from the positive terminal to the external circuit and returns to the negative terminal. DC is used in cell phones, flashlights, cars and solar panels. It can also be used for industrial processes and to transmit large amounts of power from remote locations.
  • Positive – Red wire
  • Negative – Black wire
  • Ground – White or gray wire

Here is the example of electrical wiring systems below:

Note: Before the power supply enters the home, the PEN (Protective Earth and Neutral) will be grounded and then divided into PE (earth wire) and N. This grounding system is called TN-C-S by IEC 60364 or GB 16895.

Applying Color Codes to Electrical Wiring

Most narrow wires will be color-coded by the manufacturer, using insulation of different colors. When wires are larger than #6 AWG, they will typically be manufactured with black insulation. In these cases, color coding should be added during installation, using colored bands that wrap around the wire.

How to Check and Maintain the Safety of Electrical Wiring Circuit?

Always follow appliance instructions for improved electrical safety. 

"Read the instructions" should top the list of electrical safety tips at home. Understanding home appliance safety improves both the performance of your device and your personal safety. Should any appliance give you even a slight electrical shock, stop using it until a qualified electrician checks it for problems.

Check if there are abnormal smells or black burn marks around electrical devices. 

Place a hand on outlets and light switches, checking for excessive heat. (Remember that dimmer switches often generate heat when the lights are on, but it should never be hot enough to be uncomfortable or painful to the touch.) Is there a “hot wire” smell around a switch or outlet? Turn off the power to the switch or outlet at the breaker, verify the power if off using a non-contact voltage tester, and take a closer look. You may need to replace that switch or outlet.

Finally, if you hear popping and crackling in an outlet or switch, turn off the power to the outlet or switch at the breaker, verify the power if off with a non-contact voltage tester and have the outlet or switch inspected asap.

Maintain a sound electrical wiring circuit:

Do not give much burden to the existing circuit. Normally, there are not enough power points in a room installed in the past to satisfy the growing electrical needs today. Sometimes, appliances like a server, air conditioner, microwave oven, television, satellite video box, wireless access point and other charging devices may be inserted into one wall power socket through a power strip. These appliances will draw current and cause additional strain on the ancient insulation, which is easy to cause a household electrical fire. If necessary, choose power cables supporting high-power electronic equipment and add additional wall power sockets to support the devices you need or rewiring the house with a more suitable distribution of the power points.

Keep electrical devices and outlets away from water to prevent shock:

Water and electricity don’t mix well. To follow electrical safety rules, keep electrical equipment dry and away from water prevents damage to appliances and can protect against personal injury and electrocution. When working with electrical appliances, it’s important to have dry hands. Keeping electrical equipment away from plant pots, aquariums, sinks, showers and bathtubs lowers the risk of water and electricity coming into contact.


In the United States the easiest way to remember what each wire color means is to focus on the neutral and the ground. If you see a white or grey wire you’re looking at a neutral. If you see green, green-yellow, or bare copper wire, then you’re dealing with a protective earth. You should assume that every other color is a live wire and must be treated with caution. 

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