What Is A Neutral Wire, And Why Is It Important?

Electrical circuits are constructed with at least three different wires: live, neutral and ground. Power flows in via the live wire and out via the neutral wire. If you have any fault in the neutral wire, the power won’t be able to exit the circuit, and there’ll be a possibility of surges and over-voltage. The electricity will find different paths to discharge its power - via the ground wire, earth or any other material conductor in contact with the circuit. This can lead to dangerous and unpredictable conditions, increasing the risk of electrical shock and serious equipment damage.

How Your Electrical Circuits Work

Control panels, devices and equipment are plugged into the mains power source, which sends the electricity through live wires. These wires carry the electrical load to various locations, where it may be distributed via switches or distribution panels. The live wire carries alternating current (AC) at a high voltage, 230 volts in the UK. For this reason, it’s sometimes called the “hot” wire. As long as it’s hooked up to the power source, the live wire always carries current.

To work properly in an electrical distribution system, this current must complete a circuit that returns the electrical power to its source. This is the function of the neutral wire, which completes the circuit by conveying the current back safely. This is frequently via a busbar in the switchgear or control panel. While it’s operating as the return route for the power, the neutral wire will carry an electrical current. However, in the interests of safety, it makes sense to assume that the neutral wire will always be electrically charged.

Ground wires offer extra protection against electrical overloads. Although the neutral wire is able to channel the current to some form of ground, you won’t always find a ground wire as well. Older installations won’t have them, but they do act as a useful backup. You won’t normally find any current in a ground wire, but if your wiring insulation is damaged or you have a short circuit, any unstable current will be directed through it to protect your electrical system.

Neutral And Ground Wire Confusion

People can sometimes get confused between the functions of neutral and ground wires. It’s important to remember that the neutral wire is necessary to return the current to the source, to complete the electrical circuit. It’s a key component of the live circuit, without which the electrical system won’t function. The neutral wire is also grounded to earth, so it’s capable of diverting excess or unstable current. For additional safety, most equipment will also have a ground wire specifically installed for this purpose.

In industrial settings, some circuits have four wires, especially in applications with a motor. In this type of system, you’ll have two live wires, as well as a neutral and a ground wire. The neutral wire in these circuits helps to balance the electrical load in a three-phase system, which is required for motor-driven appliances and running heavy machinery. Four-wire circuits carrying three-phase electrical current are more efficient when dealing with a large electrical demand.

In the UK, wiring colours were standardised in 2006 to comply with IEC 60446 as well as with BS7671. This made them consistent with European standards and helped to avoid confusion. Under this system, the old black neutral wire became light blue. Earth or ground wires changed from green or green and yellow to plain yellow, and live wires from red to brown. 

Loss Of Neutral

Loss of neutral is an electrical fault that can seriously impact your system. In standard electrical equipment, any breakdown of the neutral conductor will probably cause problems with over-voltage. Loss of neutral in a three-phase electrical system is far more serious.

In a three-phase transformer, the neutral wire is connected to the central point and is grounded. If this connection breaks or becomes otherwise disconnected, you’ll lose neutral. The result of this will be an imbalance in the distribution of current and voltage in the system. You’re likely to experience extremely high voltages and voltage fluctuations, which may damage your electrical equipment and even cause electrical fires.

Some of the most common ways that you might lose neutral are through severe weather, such as storms and lightning. These produce electrical interference that can damage the circuits, or cause unpredictable accidents like something falling on the wires. External wiring can also be damaged by animals or corrosion. Theft is another issue. Valuable copper wires offer a temptation to thieves, due to their high value.

To help prevent the risk of losing neutral, you can equip your system with commercial surge protection, which will protect it against temporary over-voltages. This will be in compliance with BS7671: IET Wiring Regulations, which govern the safety of UK electrical installations.

Safety First

Electricity is a dangerous commodity and must always be treated with caution. The neutral wire is an integral part of the electrical circuit and helps prevent it from overloading. Electrical current always seeks to revert to its source by any available path. In electrical terms, this is what “completing a circuit” means. As long as you provide it with a neutral wire, the circuit will be completed safely. But remember that electricity will always travel along the road of least resistance. If there’s no neutral wire or exit to the ground, the current will take any available route it can find to get back to its source.

If you have any fault in your neutral wire, the electrical current could seek a different way back. This might include diverting via water pipes, metal components, or any other conductive materials. This means there will be a danger of serious electric shocks, a safety hazard if anyone comes into contact with the charged material. In the most extreme circumstances, the electricity might use the human body as a route as it attempts to complete its circuit, which could well lead to fatal injury.