How to Trace Electrical Wiring in a Wall

By: Rosalind Jackson & Talon Homer  | 

tracing electrical wiring
Finding, or tracing, electrical wiring in walls can be tricky but it's not impossible. sestovic/Getty Images

If you need to find the electrical 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 drywall in a vain attempt to cross paths with your wires. Thankfully, there is a better way: With the right tools and techniques, you can locate— or trace— the wiring without damaging anything.

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, look for the outlets and appliances that each wire connects to.

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You also need to determine which circuit breaker applies to which section of your home's wiring. It's best to get the blueprints of the building or home you're working on before modifying electrical circuits. You can often obtain them from the local county government, or from the construction company that built the structure. Blueprints are helpful for just about every renovation, but all hope isn't lost if you can't find them.

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. Breaking into a live wire could damage your home and cause serious injury.

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Tools Needed to Trace Electrical Wiring in Walls

stud finder
A stud finder like this one is just one of the tools you can use to trace the electrical wiring behind your walls. Alex Ratson/Getty Images

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, and there are a few different kinds. A magnetic stud finder detects the metal nails in the wall studs, while an electronic stud finder produces a small electrical field that 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.

Some electronic stud finders also can detect trace amounts of electrical current behind walls. Stud finders with this feature will give you a general idea of where wires are, and where they're going, but won't tell you exactly how many wires are in that spot.

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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 volt ticks or probes. These detectors make a sound when they find a live wire.

Volt probes commonly utilize sharp pins that can be stuck into electrical outlets or breakers. Another type uses circuit-sensing clamps that can be placed over wiring insulation.

Any type of voltage detector is a crucial tool when working with electricity, as they will allow you to verify that the circuit is working correctly, or verify that it's been turned off before making modifications to the wiring. Probes can also be paired with an electronic voltmeter to give exact data for current draw and resistance.

If you have a tangle of wire and can't figure out which goes where, you can also use a tone generator to help you identify which wire is which. The tone generator consists of two devices: One that sends out a high frequency signal, and a receiver made to detect that same signal. The generator end clamps to a particular wire, sending the signal through. The receiver end can then be swept along a bundle of wires, and will let out a chirp when it finds the one that matches. This presents a simple method to find both ends of a circuit without having to physically trace the wire through a wall.

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

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Best Practices for Tracing Electrical Wiring

tracing electrical wiring
It's a good idea to make your own diagram of where your wires are and to what outlets they connect. Once you locate the paths of the wires, you can sketch them onto paper. Mikael Vaisanen/Getty Images

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.

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.

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You can find out which wires are connected to which circuit breaker without any tools at all. 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.

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

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.

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Safety Concerns When Tracing Electrical Wiring

circuit breakers
If you're planning a demolition or remodeling project, always turn off the electricity before you begin cutting into walls. Otherwise, just one cut could hit a live wire. BanksPhotos/Getty Images

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.

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Never reach into wall or floor spaces if you're not sure whether the wires behind them are live, and use non-conductive tools when working on wiring. If you have any doubts about your ability to work around wiring, then consulting a professional electrician will be the best bet.

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.

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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.

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