Whether you intend to work with electrical circuits, or just want to have an understanding of how they work, the hot or live wire is one of the most important elements to take note of.
The hot wire is the one within which electrical current passes through at all times.
Not a lot of people know how to identify it, and with wires coming in the same color, it becomes even more difficult.
Thankfully, you have come to the right place.
We explain the whole process of how to test if a wire is hot with a multimeter.
Let’s get right in.
How To Test If A Wire Is Hot With A Multimeter
Set the multimeter to the 250VAC range, place the red probe on one of the wires and place the black probe on ground. If the wire is hot, the multimeter shows a reading of either 120 or 240 volts, depending on the power output.
The process is quite straightforward, but there is more to it.
- Wear Protective Equipment
When testing if a wire is hot, you definitely expect current to be running through it.
Getting electrocuted is one thing you don’t want, so you wear protective rubber or insulated gloves before getting into it.
You also wear protective goggles in case of sparks, keep your hands on the plastic or rubber part of the multimeter probes, and prevent wires from touching each other.
As a first-timer, you practice with dead wires to avoid mistakes.
- Set The Multimeter To The 250 VAC Range
Your home appliances make use of alternating current (AC voltage) and you set your multimeter to the highest range to get the most accurate reading.
The 250 VAC range is optimal, as the highest voltage reading you expect to get from home appliances and power outlets is 240V.
- Open Up Outlet
To test which of the wires in a wall outlet is hot, you need to open up the outlet.
Just remove any screws holding the pieces together and bring the wires out.
There are typically three wires in the outlet and these are the live, neutral, and ground wires.
- Place Probes On Wires
Ordinarily, only the live or hot wire holds current when exposed, and this makes the whole test even easier.
Place the red (positive) probe on one wire and the black (negative) probe on ground.
- Evaluate Results
Once you position your probes, you check the multimeter for a reading.
If the multimeter presents a reading of 120V (with wires for lighting) or 240V (with outlets for large appliances), then that wire is hot or live.
Remember that the hot wire is the one that the red probe is on when you get this reading.
The black probe remains grounded.
Other wires (the neutral and ground wires) show you a zero current reading.
Use a paper or masking tape to label the hot wire so you easily identify it in the future.
Here is a video that shows exactly how to identify hot wire with a multimeter:
If you did not get a reading from the multimeter, there may be a problem with the wires. We have an article on tracing wires with a multimeter.
There are also other ways to identify which of the wires is hot.
Using A Non-Contact Voltage Tester
An easier and safer method of identifying which of the wires is hot is to make use of a non-contact voltage tester.
A non-contact voltage tester is a device that illuminates when it gets in proximity with electrical current. It doesn’t have to make contact with the naked wire.
To test if a wire is live or not, you simply place the tip of the non-contact voltage tester on the wire or outlet port.
If a red light (or any type of light depending on the model) illuminates, then that wire or port is hot.
Some non-contact voltage testers are additionally designed to make beeping sounds when in proximity with voltage.
Although this device is safer to use, the multimeter is an all-rounder for testing other electrical components.
Using Color Codes
Another method of identifying which wire is hot is to make use of color codes.
Although this method is the easiest, it isn’t as accurate or efficient as other methods.
This is because there are different color codes for wires used in different countries and, sometimes, all the wires could come as the same color.
Check out the table below to identify the common color codes for your country.
The single-phase line represents the live or hot wire.
As you see, color codes are not universal and you can’t entirely depend on them.
Identifying which of your wires is hot is one of the most straightforward procedures to carry out.
While being careful, you simply make use of a multimeter to check for voltage readings.
If this was helpful, you may check out our articles on testing other electrical components using a multimeter.
Frequently Asked Questions
Which Wire Is Hot When Both Are Same Color?
The hot wire brings up a reading on the multimeter when tested. You check by placing the red probe on a wire and placing the black probe on ground to get a 120VAC or 240VAC reading.
How Do You Test A Hot Wire With Ground?
To test a hot wire with ground, you need a multimeter. Place the red probe on one wire and place the black probe on ground. The hot wire presents you with a reading of either 120VAC or 240VAC.
How Do I Make Sure My Power Is Off With A Multimeter?
Set your multimeter to the highest AC voltage range, place the red probe on a wire, and place the black probe on ground. If your power is off, the multimeter does not show any voltage reading.