Home Electrical Wiring Color Code Standards

The standard color of the electrical cable in the single phase home electric grid, where there are 3 (three) wires with different colors, namely blue, yellow, black. This cable colour code (CCC) for fixed electrical installations are applicable in some countries such as: Indonesia, Singapore, Hong Kong,, Russia, etc.. For other regions such as US and Europe, please read below explanation.

The basic principle of the circuit can be described as the schematic above.

The blue wire is used for a neutral electric charge or neutral conductor. Sometimes it is also called the negative wire.

Yellow or green wire, or yellow-green striped, for ground or earth, or protective conductor. This wire is sometimes has no insulation or bare wire, directly wrapped with an outer insulator of the cable, which is usually white.

Black or dark brown wire, as active wire that are electrically charged, are also referred to as: phase, live fire, hot, positive.

Actually the term positive wire and negative wire are not quite right. Because the grid has alternating current (a/c). So the black and blue wires will alternate as positive and as negative.

The hot wire must pass through a fuse or MCB (Miniature Circuit Breaker). So that the current can be cut off in case of damage or short circuit, or when repairing the electric grid. The photo above shows a Philips MCB.

The blue wire is neutral, it is connected to earth or ground in the distribution transformer. Or in the generator set, if the electric grid does not pass through the transformer. That is why this wire has no voltage, when touched by fingers or hands. If it is touched by an electric test pen, the neutral wire also does not turn on the test pen light. Actually there is still voltage in the neutral wire, but the voltage is very weak.

The ground wire (green yellow) is connected to ground or earth. The house must have grounding system for this wire to work. The ground wire is connected to a metal body, chassis or metal frame of electrical devices, such as: refrigerator, air conditioner (a/c), washing machine, dishwasher, desktop computer, tv (television), water heater, room heater, clothes iron, audio device (sound system), and others. So that if there is a leakage of electric current, it can be directly discharged to the ground. Thus preventing electrocution, if someone touches the body of an electrical device. On audio device, grounding can improve sound quality to be clearer, because it removes unwanted signals (noise).

Ungrounded soldering can damage sensitive components such as ICs, transistors, MOSFETs, etc.. But many soldering irons are not earthed. Because of the consideration that the price is cheaper, and the cable is lighter so that the solder is easy to move.

If it is grounded, some experts think it's best to ground the soldering rod through a resistor with value about 100 kilo ohms to 1 mega ohms. So if the soldering rod touches the live voltage circuit, then the resistor prevents the electric current from flowing to the ground through the solder rod. This can interfere a working circuit, or even damage sensitive circuit.

In most houses, the power grid is permanently grounded via a metal rod embedded into the ground. The metal can be: stainless steel pipe, copper, galvanized pipe, aluminum, which extend from inside the house, to moist soil or water in the ground.

The depth of the grounding conductor depends on the ground conditions. Conductor can be planted shallowly if the soil condition is always moist throughout the year. Generally, a depth of 4 to 8 feet, or about 1 to 3 meters is quite safe.

A good grounding has resistance below 5 ohms, by measuring it with an earth resistance tester.

If there is a lightning rod installed in a house or building, the grounding will conduct a lightning electric current into the ground. The grounding system for lightning must be separated from the grounding of the power grid. In order to prevent lightning electric current to enter to the power grid, and damaging electrical devices and electronic equipments.

Clean water network pipes in urban areas can be used as grounding. Especially if the pipe is always full of water. But disturbances in the surrounding environment can produce electric current flow back to sensitive equipment in the house. So that it interferes and even damages sensitive electronic device. In some areas, grounding via the clean water network is prohibited, one of the reasons is because electricity can cause electrolysis and damage water quality.

Grounding can also be connected to the home water pump metal body, although the pump suction pipe is made of PVC (Polyvinyl chloride) plastic. As long as the suction pipe and water pump are fully filled with water, earthing will be good. But if the water is reduced, then the grounding is not good. When the water is reduced, chances are the water pump will work hard and then short circuit. So that the electric current leaks, and damages other equipment that is grounded via the water pump.

So grounding via clean water channels is only suitable as temporary grounding. For the long term must use separate and permanent earthing.

For United States (US) a/c power circuit wiring color codes

Protective ground: bare, green, or green-yellow

Neutral : white or grey

Line, single phase: black

IEC (International Electrotechnical Commission) AC power circuit wiring color codes, applicable for most of Europe:

Protective earth: green-yellow

Neutral : blue

Line, single phase: brown

More detail about wiring rules can be read on Wikipedia Electrical wiring.