How to Trace Electrical Wiring in a Wall

By: Rosalind Jackson  | 

With the right tools and techniques, you can trace your wiring without damaging your walls. ­
With the right tools and techniques, you can trace your wiring without damaging your walls. ­

­If you need to find the wires inside your walls, you'll probably want a non-invasive way to look for them. After all, without a method to your madness, you'd just be hammering unsightly holes through your drywall in a vain attempt to cross paths with your wires. Instead, there's a better way: With the right tools and techniques, you can locate, or trace, your wiring without damaging your walls.

Tracing electrical wiring in walls can be tricky, and it involves more than just looking for the wires themselves. To figure out exactly where the wires are, you'll look f­or the outlets and appliances that each wire connects to. You'll also figure out which circuit breaker applies to which section of your home's wiring.


­You may be wondering why someone would go through all that trouble just to figure out the locations of wires. Knowing where your wires are can help you make repairs, plan for home improvement projects and even make your home safer. By knowing which outlets are on which circuits, you can decide where to plug in power-hungry appliances without overloading your electrical system. If one of your outlets is on the fritz and you don't have an electrical blueprint of your home to use as a reference, tracing the wiring can help you figure out exactly where the problem is. If you want to run new wires to a home theater system or other electronics, knowing your current wires' locations can help cut down on electrical interference, which can lower the quality of your picture and sound. And you'll definitely need to know where the wires are if you plan to do any renovation or demolition projects to your inside walls. Breaking into a live wire could damage your home and cause serious injury.

Read the next page to find out what tools you need to trace electrical wiring in walls.


Tools Needed to Trace Electrical Wiring in Walls

You can use a range of tools to trace electrical wiring in your walls, and some of the tools you already have might help you in your project, too. One such tool is a stud finder. A magnetic stud finder detects the metal nails in the wall studs. An electronic stud finder produces a small electrical field, which changes when it reaches a denser region of the wall -- like the area over a stud. The stud finder's circuitry detects this change and lets you know with a light or a sound [source: Berendsohn]. Some electronic stud finders also have the ability to detect wires behind walls.

Voltage detectors are helpful once you find your wires -- they let you test whether the wires are live. A neon-bulb version, also known as a neon circuit tester, is an inexpensive tool used for the purpose of detecting voltage. Another option is an audible alarm voltage detector. These are also known as tone generators and probes or tone and probe kits. Tone generators make sound when they find a live wire. If you have a tangle of wire and can't figure out which goes where, you can use the probe to help you identify which wire is which.


You can also buy circuit and wire tracers made specifically for the purpose of locating electrical wiring behind walls and underground. These tools tend to be expensive, though, making them most suitable for professionals and people who plan to do lots of wiring work.

Tracing electrical wiring can be tricky and involved. Click to the next page to discover the best practices for tracing electrical wiring.


Best Practices for Tracing Electrical Wiring

­All-in-one wire tracers come with instructions that allow you to trace the wiring in your walls. You can also use stud-finders with wire-sensing modes to track down specific wires. But you can also get a good idea of where your wires are without such sophisticated devices. There's no one right way to do it. The method you choose simply depends on what your purpose is for tracing wires and what works best for you.

You can find out which wires are connected to which circuit breaker without any tools at all. If you have any kind of electrical wiring blueprint for the building you're testing, this is a decent method to use. If you already know where the wires run behind the walls, testing the circuit breakers simply verifies that the wires and switches are connected. Work with a partner -- one of you should stay at the breaker box to flip the switch, and the other should observe which outlets get power. You can do this without a partner as well, although running back and forth between outlets and breakers is time- and labor-intensive.


Start with all the breakers off, and plug a lamp -- turned on -- into an outlet. Flip breakers on and off one at a time until the lamp lights up. Then, plug the lamp into the other nearby outlets to determine which ones are on the same circuit. Flip light switches to see which circuit the lights are on. Circuits that run to large appliances, like clothes dryers, often have no other outlets or appliances on the circuit.

Another practice of finding electrical wires behind walls is to use a metal detector. This can be an efficient method if you know there are very few wires and if there aren't many other metal objects, like nails, in the walls.

If you're tracing electrical wiring so you can add new outlets or lighting, or if you're getting ready to make electrical repairs, you'll need your voltage detector and other tools for safety reasons. Read on to the next page for more on safety when tracing your electrical wiring.


Safety Concerns When Tracing Electrical Wiring

Any project involving electricity can be dangerous. For this reason, some areas allow only licensed electricians to repair or add to a home's wiring. Before you start, consult your local laws as well as any building codes that apply to your project. Faulty wiring can cause a fire or electrocution, so follow directions to the letter and consult a professional if you have questions.

If you're working on lighting, outlets or wiring, cut the power at the circuit breaker first. If you need to test wires while you're tracing, use caution. Handle all your tools with care, and wear gloves and eye protection if you need to cut into the wall or floor to find or fix your wires. Handle hammers and saws carefully, and keep an eye out for exposed nails, wires and other potentially dangerous items. Never reach into wall or floor spaces if you're not sure whether the wires behind them are live, and use nonconductive tools when working on wiring.


If you're going to use the method of switching the circuit breakers on and off, keep in mind that you'll be in the dark as you move from one location to another. Don't cut the power to areas where lights are necessary for safety reasons. Before flipping circuit breakers on and off, unplug appliances so they aren't damaged by the constant changes in power.

To learn more about tracing electrical wiring, visit the links on the following page.


Originally Published: Mar 24, 2009

Wire Tracer Tool FAQ

How do I find electrical wires in a wall?
There are two kinds of stud finders that can help you find wires in a wall – magnetic and electric.  A magnetic stud finder is used to detect metal nails in wall studs. Electronic stud finders produce a tiny electrical field that changes when the finder reaches a denser region in a wall.
How do wire tracers work?
Wire tracers help locate both energized and de-energized cables, wires and pipes, no matter where they’re hidden. By bouncing a signal off a target pipe or wire, it helps determine the target and direction it's going in.
How does a tone tracer work?
A tone generator sends a signal into the cable so that it can be traced. It is a square wave reverberating a warbling tone. An Inductive Amplifier is a probe tool, working by capacitive coupling from the tone injected on the wire.
What is a tone generator used for?
Tone generators are used to send a tone signal into a wire pair or single conductor. Technicians can identify a single wire buried in a bundle by combining it with an amplifier probe.
How far into the wall are wires located?
Wiring usually runs horizontally, about an inch into the wall. The parameters are 6 inches or 12 inches above the receptacle.

Lots More Information

Related HowStuffWorks Articles

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  • Black & Decker. "Carpentry: Remodeling." Googlebooks. (Accessed 3/16/09),M1
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