How to Identify Live and Neutral Wire Using a Multimeter?

Last updated on June 8th, 2023 at 12:28 pm

The safest and easiest way to identify live, neutral, and earth wires in a household electric system is by using a digital multimeter. First, select the appropriate AC voltage range(higher than the supply voltage in your area) on your multimeter. Then use the hit-and-trial method to check the voltage differences between different wires. It would help if you had a basic understanding of supply wires.

To test if a wire is live, neutral, and earth, you have to follow these steps:

• Select the appropriate AC voltage range on your multimeter.
• By measuring the voltage difference between wires, determine the live wire first(discussed below).
• Determine neutral and ground out of the remaining two wires.

What is the voltage of Live, neutral, and earth wire?

The ideal voltage of live, earth, and neutral wires in a 220V electric system is 220 V, 0, and 0, respectively. In a 110V electric system, it’s 110 V, 0, and 0, respectively.

Why is the voltage between neutral and earth, not zero?

Ideally, the voltage between neutral and earth is zero. But in practical situations, there is some voltage difference between them. Why? Because the neutral wire carries the same current as the live wire, while the earth wire has zero current.

The neutral wire has some resistance, typically due to its length and connections. And since current flows through it, this resistance results in a voltage difference between the neutral and earth. Which is the product of the neutral wire current and its resistance.

For example, if a 5A current flows through a 200 ft long 12 ga wire with a resistance of 0.30 ohms, the voltage drop across the neutral wire will be 1.50V. Meanwhile, the earth wire will have no voltage drop. Thus, there will be a 1.50V AC difference between the earth and neutral at the load.

In a real case scenario, if the voltage between Live and Earth is 230 volts: The voltage between Live and Neutral, Neutral and Earth is around 225V – 229V and 1V – 5V, respectively.

How to check a Live wire using a multimeter?

• First, select the AC voltage function having a “V~” symbol on your multimeter.

To select the appropriate range(higher than your domestic supply voltage), you must know your country’s domestic supply voltage. It will either be 110V or 220V. (Read more)

• Now take any two wires and, using the multimeter, measure the voltage difference between them. If the multimeter shows 220 to 230 volts, one of the wires is the live wire. Let’s call them Wire A and Wire B.

• Take the third wire(Wire C) and measure the voltage difference between it and Wire A and B separately. If the voltage between wires A and C is close to what you measured before(220V – 230V), Wire A is the Live wire. If it’s different(1V to 5V), and the voltage between wires B and C is close to what you measured before, Wire B is the Live wire.

In my case, Wire A is the live wire.

How to check Neutral and Earth Wires using a Multimeter?

To test which wire is neutral and earth out of the two(Wire B and C), you have to measure the voltage between Wire A and either one of them.

If the voltage between A and B is less than between A and C(approximately 1V to 5V), wire B is the neutral wire and vice-versa. Wire C is the earth wire in this case.

Identify live, neutral, and earth using the color code

Different colors are used in electrical wiring to identify the live, neutral, and earth wires. Please note that the color codes may vary depending on the country or region you are in. Follow the color code table for the same:

Note: You should never rely on this method to identify wire types due to inconsistent standards and the possibility of improper modifications, mislabeling, and mistakes.

FAQs

Do both live and neutral have voltage?

In an ideal electrical system, the voltage of both live and neutral is zero with respect to the earth/ground wire. But since neutral wire also carries current equal to the live one, there is a voltage drop due to its resistance, typically between 1-5 V. So yes both live and neutral have voltage.

What is the voltage between the live and neutral wire?

In a real electrical system, the voltage between live and neutral is less than the actual live wire voltage. If voltage between live and earth is 230V, then the voltage between live and neutral can be anywhere between 225V to 229V.