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.