How to Identify the Neutral Wire Using a Multimeter?

Question

I’m working on some wiring in my old house, but all the wires are the same color, which has made it tricky to figure out which one is the neutral wire. I want to avoid any mistakes, so I’m hoping to get some guidance on how to correctly identify the neutral using a multimeter.

Admin · Accepted Answer

Hey there! Here's a quick, step-by-step guide to identifying live, neutral, and earth wires using a digital multimeter:

Set Up Your Multimeter:
Choose the AC voltage mode and set the range higher than your local supply (e.g., 220V or 110V).
Identify the Live Wire:
1. Label your three wires as A, B, and C.
2. Measure the voltage between A and B, B and C, and A and C. The pair that shows ~220V (or 110V) contains the Live and Neutral wires. For example: 220V between A and B i.e., one of them is live.
3. Then, measure between one of these (A) and the third remaining wire (C).
  - If A to C also reads close to 220V (or 110V), then A is likely to live.
  - If it’s much lower (around 1-5V), then the live wire is the other one (B).
Determine Neutral vs. Earth:

Now measure the voltage between the identified live wire and the remaining two wires i.e., first between A and B, then between A and C
- The wire with a lower voltage difference (around 1-5V) compared to the live wire is neutral. For example: Bw A and B = 215 and BW A and C = 220. In this case, wire B is neutral
- The other wire, showing nearly 0V less than the neutral is your Earth i.e., wire C is Earth.

Keep in mind: Ideally, live should be around 220V (or 110V), while neutral and earth are close to 0V (with a slight drop of 1-5V on neutral due to resistance).

For a deeper dive and more detailed instructions, check out this article: How to Identify Live, Neutral, and Earth Using a Multimeter.

Sebastian · Answer

To identifying the Neutral Wire Using a Multimeter you have to follow the steps below.

Set Up the Multimeter: Switch your multimeter to an AC voltage range above your circuit’s expected voltage.
Connect the Probes: Insert the black probe into the "COM" port and the red probe into the "V" port on the multimeter.
Test Each Wire:
- Touch the black probe to a known ground (like a metal box or a ground wire).
- Use the red probe to test each wire individually:
  - A high voltage reading indicates a live wire.
  - A near-zero reading (under 1V) usually points to the neutral wire.

This method should reliably help you find the neutral wire. Remember to always turn off the power before making any connections, and re-energize only for testing.

Kanishk · Answer

This is the safest option to identify the Neutral wire using a multimeter:

1. Set Up Your Multimeter:

Set your multimeter to AC voltage mode (V~).
Choose a range higher than your supply voltage (e.g., 250V for 220V systems).
Insert the black probe in COM and the red probe in V/Ω.

2. Identify the Live Wire:

Place the black probe on a known earth source (e.g., a metallic pipe or grounded screw).
Use the red probe to measure each wire.
- Live to Earth = ~220V (or 110V)
- Neutral to Earth = 0V - 5V
- Earth to Earth = 0V
The wire showing the highest voltage (~220V or 110V) is Live.

3. Identify Neutral vs. Earth:

Measure the voltage between the remaining two wires.
Neutral to Earth should show 0V - 5V due to minor voltage drop.
Earth to Live should still show ~220V (or 110V).
The wire showing nearly 0V relative to Earth is the actual Earth wire.