Neutral wires are not as neutral as they sound, often carrying the same amount of electricity as any other wire in the power system. In a confusing tangle of cables and wires, industry standard wire color codes are used to communicate to electricians, maintenance workers, and employees the function of the wire how many volts that particular wire is carrying. Often, the quickest way to identify electrical wiring is by its color.
Neutral wires work as a circuit conductor, carrying power back to the source and completing the circuit. The return path a neutral wire provides is a hallmark alternating current (AC) systems, meaning no neutral wires are used when wiring for direct current (DC) power. In a single panel installation, neutral wires are connected at two points, one of them usually being the ground (earth).
In the United States, the National Electrical Code (NFPA 70) standardizes wire color codes, including requirements for neutral wire colors. Only two colors are approved for neutral wires, dependent on the type of AC power being used.
- AC Power (120/208/240 volts): Neutral wiring should be indicated using a white wire.
- AC Power (277/480 volts): These high-voltage connections are much more powerful making them ideal for industrial systems. In this case, neutral wires should be grey.
It’s important to understand what system is being used and have the correct color wires because the difference between the two systems can be a deadly amount of electricity.
Neutral wires and ground wires are often mixed up and used interchangeably, but these are two different types of wires and must be color coded as such. Ground wires work to provide a low-impedance path to prevent hazardous spikes in voltage and will normally not carry any current. Ground wiring should be solid green, green with a yellow stripe in the middle, or copper.