How to Safely Check if an Electrical Wire Is Live

How to Safely Check if an Electrical Wire Is Live

Electrical
Lighting
By Mateos Glen Hayes November 07, 2022

Testing an electrical wire to check if it’s live is something that requires care and proper procedure for the sake of safety. As general rules, you should never test wires unless you are a qualified electrician, and you should not work on any live wire until the power supply is turned off. 

With that being said, it is important to know the right steps to take to safely test a live wire as this can be necessary over the course of renovations. Even something as simple as a light switch installation or as complex as an electrical fault may require you to test for live wires. Furthermore, the procedure for testing for live electrical wires differs depending on where the live wire is. Knowing the correct precautions will keep you safe and allow you to do electrical work without worry. 

Wire Tester Types 

Different wire testers work best for different applications and some provide more diagnostic data than others.

Different wire testers work best for different applications and some provide more diagnostic data than others.

There are a few tools out there that can help you test for live wires, each of which has its own sets of drawbacks as well as advantages. While it is technically possible to use any one of them, you may choose to use one over another based on where the potential live wire is. Depending on location, some live wires may be difficult to get to, and as we will see, some of these tools can help with that challenge. 

The safest way to check an electrical wire for current is with a voltage live wire tester. There are other tools including electrician’s screwdrivers, but we do not recommend using these unless you are a certified electrician who has a good knowledge of electrical grounding. Without this, the risk of electrocuting yourself - for example through a hot black wire - is much higher.

Digital Multimeter

Multimeters are a device with many uses. They can be used to give you precise measurements of amperage, voltage, and ohmage (a fancy word for electrical resistance measured in Ohms). Multimeters can also function as live wire testers. Simply set the device to “AC”(Alternating Current) mode, and connect the two probes to their corresponding polarity wires.

Digital multimeters provide precise readings for various values you might need to know as an electrician.

Digital multimeters provide precise readings for various values you might need to know as an electrician.

Typically these wires are color coded red (positive) and black (negative). Be sure that the power is switched off before you check that the electrical cable is live. If the multimeter picks up a reading this will be displayed on its LCD screen, typically to the nearest two decimals. Because it gives you more precise readings, you can also test to ensure that electrical wiring is properly grounded - a useful feature if you live in an older home. 

Non-Contact Live Wire Tester 

For maximum safety, you need a non-contact live wire tester. This is the safest way to test if a wire is live because you don't need to touch any wires to get a reading. Instead, this simple device works by taking a reading from electrical sockets, so all you need to do is insert it after turning off the power.

Because these live wire testers are plastic and resin coated, they are quite safe to use as these materials are not conductive. If the wire is live, the device will let you know by beeping continuously. Of course, this device cannot be used to help you test electrical wiring that is not accessible by outlet and it does not give precise voltage readings like a multimeter, meaning it will not be the best solution in all situations.   

Different Locations and How to Check for a Live Wire

Non-contact wire testers provide an easy and safe way to test circuits in your home.

Non-contact wire testers provide an easy and safe way to test circuits in your home.

Alas, not all electrical wire tests are straightforward. If you find yourself redoing wiring as part of a home remodeling or trying to root out a fault in a spider’s web of wiring, things become a bit more complicated. With this in mind, it is important that you are able to identify various wires and what they do, and also know how to test for live wires in various situations.  

Color Codes 

If you end up working on wires directly, meaning not through a socket or an electrical panel, you’re going to need to know what each wire in a given circuit does. Fortunately, electrical wiring in the US is standardized according to colors, thanks to the National Electrical Code. Neutral wires are white or gray, and protective ground wires are green or green-yellow. Additionally, there are 208 volt AC wires that are black, red, or blue, and 480 volt AC wires that are brown, orange, or yellow. 

It is highly recommended that you wear insulated high-voltage safety gloves when working on exposed wiring.

It is highly recommended that you wear insulated high-voltage safety gloves when working on exposed wiring.

Behind a Wall

Sometimes, the electrical wire that you want to test is behind a wall. If that is the case, cutting through the drywall is an extra step you might prefer to avoid as it makes a huge mess and adds time and complexity to any electrical project. In this case, what you need is a UWB or ultra-wideband device. This device allows you to detect and test live electrical wires behind a wall in a matter of seconds without removing any drywall. 

This device wasn’t mentioned earlier because it is an advanced professional electrical wire tester and quite pricey to boot. These devices are also not very user friendly and so you either need to be trained as an electrician or have someone who is an electrician to help you use it.   

Exposed Wires 

Exposed wires are inherently more dangerous to work with and so extra care is always required if this is a mandatory part of your electrical project. As such, it is highly recommended that you wear a pair of insulated high-voltage safety gloves if you plan to handle exposed electricity wires

Another good precaution is to stand on an insulated rubber mat to further reduce the risk of electrocution. To test exposed electricity wires, place one lead from a multimeter on the ground (any metal surface) and then place the other lead so it touches the exposed wires. 

Usually, you will have three exposed electrical wires. One is earth and another is neutral, and neither should give any reading other than zero or near zero. The third wire is the hot one, and so this one should cause your live wire tester to produce a 110V reading, assuming everything is working normally. 

Testing the wires within a switch circuit requires you to remove the switch first.

Testing the wires within a switch circuit requires you to remove the switch first.

Switches

Whether you’re searching for an electrical problem or just replacing a switch, it’s a good idea to know how to test the wiring in your light switches as well. The procedure for testing a live electrical wire in a switch requires a few steps, but is ultimately fairly simple. After turning off the power, remove the plastic cover on the switch by unscrewing it. Once the cover is off, remove the switch itself by unscrewing screws from the metal mounting brackets on either side and disconnect the switch from its electrical wires by removing the corresponding screws. 

You should now have three wires, much as you would if testing exposed wiring. And as with exposed wiring, the procedure for testing the electrical wires is the same. Get your multimeter and place one test lead on the ground (a piece of metal) and the other on the wire you are testing. You can use the standardized color schemes to determine which wire is which, and the multimeter will show you if each wire is working as it should (two with zero or near zero reading, one with 110V reading). 

Safety Tips 

Safety is always a paramount consideration when working on electrics, regardless of what precisely you are doing and how simple the procedure may seem. With that in mind, here are a few safety tips to take note of so that the live electrical wiring test goes smoothly. 

Emergency Electricians

At the end of the day, the internet is a truly bountiful source for any homeowner or handyperson who finds themselves in a jam. If you don’t feel safe or comfortable working on some electricity wiring, or you’re unsure of what to do, remember there are always people you can get in touch with. Certified pros can either offer you advice or complete a thorough electrical inspection of your home for you. 

Always switch off the power before beginning work to reduce the risk of electric shock.

Always switch off the power before beginning work to reduce the risk of electric shock.

Unplug and Turn Off 

You know this is an important step because we repeat it multiple times. It is always crucial that you turn off the power before doing any kind of work on the electrics in your home. Likewise, if you are working on an appliance, you must ensure that said device is unplugged so that it does not pose a shock hazard. 

Watch Out for Backup Power Sources

Additionally, if you plan to work on your electrics or on an appliance, be mindful of backup power sources. In an appliance, this can mean batteries, capacitors, or an uninterruptible power supply unit. Homes can also be installed with inverters, especially in places with rolling blackouts, and these are designed to automatically come on when power from the mains is lost. When working on circuits that feature any of these accumulating devices, either ensure they are turned off or wait for them to exhaust their charge before proceeding. 

MG

Written by
Mateos Glen Hayes

Written by Mateos Glen Hayes

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