How to check if a wire is hot with a multimeter
Content
Whether you're about to work with electrical circuits or just want to understand how they work, a hot or live wire is one of the most important things to look out for.
A hot wire is one through which an electric current is constantly passing.
Few people know how to identify it, and with wires of the same color, it becomes even more difficult.
Fortunately, you have come to the right place.
We explain the whole process of how to check if a wire is hot with a multimeter.
Let's get started.
How to check if a wire is hot with a multimeter
Set the multimeter to the 250VAC range, place the red test lead on one of the wires, and place the black test lead on ground. If the wire is hot, the multimeter shows either 120 or 240 volts, depending on the power output.
The process is quite simple, but that's not all.
- Wear protection
When you test to see if a wire is hot, you definitely expect current to flow through it.
Being electrocuted is something you don't want, so put on protective rubber or insulating gloves before getting into it.
You also wear goggles in case of sparks, keep your hands on the plastic or rubber part of the multimeter's probes, and keep the wires from touching each other.
As a beginner, you train with de-energized wires to avoid mistakes.
- Set the multimeter to the 250V AC range
Your appliances use alternating current (AC voltage) and you set your multimeter to its highest range to get the most accurate reading.
The 250VAC range is optimal because the maximum voltage you would expect from appliances and electrical outlets is 240V.
- open exit
To check which of the wires in the outlet is hot, you need to open the outlet.
Simply remove all screws holding the pieces together and pull out the wires.
Usually there are three wires in the socket: phase, neutral and ground.
- Place sensors on wires
Usually only a live or hot wire will hold current when it's open, and this makes the whole test even easier.
Place the red (positive) test lead on one wire and the black (negative) test lead to ground.
- Rate results
After you position your probes, you check the multimeter readings.
If the multimeter reads 120V (with lighting wires) or 240V (with large appliance outlets), the wire is hot or live.
Remember that the hot wire is the one with the red probe when you get this reading.
The black probe remains grounded.
The other wires (neutral and ground) show zero current readings.
Use paper or masking tape to mark the hot wire so you can easily identify it in the future.
Here is a video showing exactly how to determine the hot wire with a multimeter:
If you don't get a multimeter reading, the problem might be with the wires. We have an article about finding wires with a multimeter.
There are other ways to determine which wire is hot.
Using a non-contact voltage tester
An easier and safer way to determine which wire is hot is to use a non-contact voltage tester.
A non-contact voltage tester is a device that lights up when an electrical current is applied to it. It must not come into contact with bare wire.
To check if a wire is live, simply place the tip of the non-contact voltage tester on the wire or outlet.
If the red light (or any other light, depending on the model) is on, that wire or port is hot.
Some non-contact voltage testers are additionally designed to beep when near voltage.
While this device is safer to use, the multimeter is a versatile tool for testing other electrical components.
You can optionally use a multimeter to check which wire is neutral and which is ground.
Using color codes
Another way to tell which wire is hot is to use color codes.
Although this method is the simplest, it is not as accurate or efficient as other methods.
This is because different countries use different wire color codes and sometimes all wires can be the same color.
Please refer to the table below to determine the common color codes for your country.
A single-phase line is a live or energized wire.
As you can see, color codes are not universal and cannot be completely relied upon.
Conclusion
Determining which of your wires is hot is one of the easiest procedures.
Being careful, you simply use a multimeter to check the voltage reading.
If it was helpful, you can check out our articles on testing other electrical components with a multimeter.
F.A.Q.
Which wire is hot if both are the same color?
The hot wire shows the multimeter reading when testing. You test by placing the red probe on the wire and placing the black probe on ground to get a reading of 120VAC or 240VAC.
How do you test a hot wire to ground?
To test the hot wire to ground, you will need a multimeter. Place the red test lead on one wire and place the black test lead on ground. The hot wire shows a reading of 120VAC or 240VAC.
How to make sure the power is off with a multimeter?
Set the multimeter to the highest AC voltage range, place the red test lead on the wire and the black test lead on ground. If your power is off, the multimeter does not show any voltage reading.
