The first thing you will notice when you open up a circuit box is the different coloured wires. Black, red, white — each wire in the box has its own purpose. While the wiring codes might be different all over the world. Electrical wiring colours are colour-coded to indicate the function they serve in the electrical wiring in a house.
The United Kingdom now follows the IEC AC wiring colour codes. The table below lists all the new and old ones.
| Function | label | Colour, IEC | Old UK colour |
|---|---|---|---|
| Protective earth | PE | green-yellow | green-yellow |
| Neutral | N | blue | black |
| Line, single phase | L | brown | red |
| Line, 3-phase | L1 | brown | red |
| Line, 3-phase | L2 | black | yellow |
| Line, 3-phase | L3 | grey | blue |
in this article
Hot Wires
Hotwires are the first to supply power to a circuit and carry the current to the electrical outlet from the power source.
The colours of hot wires are
Black Wires: These wires carry power from an electrical panel to a destination like a light bulb or an outlet. These wires are termed hot wires and are a part of household circuits. Black wires are never used for ground or neutral wiring — nor should they be used for any other purpose than carrying live electrical loads.
Red Wires: Red insulation is also used to designate hot wires. They are secondary hot wires in 240-volt installations. Red wires are also used as the interconnection between smoke detectors, which are hardwired into the system. This means that if one alarm is triggered, all others go off simultaneously. A red wire can be connected to another red wire or a black wire.
White Wires with Black or Red Tape: When a white wire has black or red tape, it is being used as a hot wire.
Blue and Yellow Wires: Blue and yellow wires are sometimes used as hot wires inside an electrical conduit.
Neutral Wires: The term neutral is a dangerously deceiving term to imply to a non-electrified wire. Neutral wires can also carry power in the electrical wiring in a house.
After the hot wire carries current at the beginning of the circuit, the neutral wire has the current back to the original power source — the neutral wire carries the course to the ground connection at the electrical panel. This means that the current circulates through the electrical system and follows electricity to be fully utilised. It also prevents faulty or excess currents.
Colours of neutral wires
White and Gray Wires: White and grey insulation indicate neutral wires. White colours interconnect a ground bus bar (a conductive metal that attracts electric current for distribution outward to feeders.) You can connect white and grey wires to only white and grey wires.
Ground Wires: These are bare wires connected to metal parts in appliances like microwave ovens and coffee pots. They are a safety feature if hot or neutral wires have come in contact with metal parts. Connecting a ground wire to the earth eliminates the possibility of shock if there is a short circuit.
Green Wires: Green insulation indicates the grounding of an electric circuit in electrical wiring colours. A green wire can only connect to another green wire. Green cables run from the outlet box to the ground bus bar within an electric panel. This way, the green wire can provide a path to the current if a live wire in the circuit touches metal or some other conductive metal.
Not all homes have green wiring, but newly built homes are mandated to have green wiring after a law passed by the NEC. Houses where there are outlets with three prongs have green wire, and houses with only two prongs don’t have a ground wire.
Electrical Wiring Tips
Now that you know the electrical wiring colour code, here are a few tips for electrical repairs. Dealing with electrical wiring in a house is all about safety since an improper current passage can mean an electrical current.
1. Make Sure the Power Supply is Off
When doing a DIY job repairing electrical wiring, the first step is to be extra mindful of the safety precautions. One of the first steps you should take is shutting down the power at the circuit breaker. Then you need to test the wires and devices for power with a non-contact voltage tester before you start working on them.
2. It’s Imperative to Choose the Right Amperage
When you are replacing a light fixture, switch or working on any other power outlet, you need to make sure the device’s amperage matches that of the circuit. Especially when you are replacing a power outlet, you need to make sure the power outlet you are working on matches the amperage of the course.
For example, installing a power outlet or receptacle rated at 20-amps in a 15-amp circuit is a surefire way to cause a short circuit. But there is no danger in installing a 20-amp receptacle in a 20-amp circuit.
3. Make Sure Your Wiring Connections Are Tight
Electricity travels along conductors like wires and metal contacts of outlets and sockets. Loose connections can disrupt the flow of electricity from one point to another, creating friction and heat.
Very loose connections can lead to arcing, where electricity jumps in the air from one conductor to another, creating tremendous heat.
The way to prevent fire hazards from loose connections is to ensure the wire connections are tight and have complete contact of the conductors being joined.
4. Grounding and Polarization Are Important
Grounding is a safe path for stray electrical currents caused by any problems in the circuit. Polarisation stops electrical current, which travels from the source of hot wires and returns to the head through neutral wires.
5. An Electrical Box Is Important
National Electrical Code mandates that all wiring connections can be made in an enclosure, like an electrical box. Enclosure act as insulators to protect people from accidental contact with those connections. They also provide means for securing conductors and devices.
Whenever you take on a project like electrical wiring in a house by yourself, you must lay a premium on safety, since electrical wiring can be dangerous. It is best to take the help of an electrician in case a DIY job seems too intimidating.