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How can I work out where an electrical cable runs through walls/floors?

I am building a circuit map of a 1941 house with unfinished basement. I shut off all circuits at the main service panel, switch on the circuit I wish to trace, and track the cable from the panel and through the basement till it disappears into the floor above, then run upstairs and see what's powered and tag it. 2 cable runs I have tracked to where they disappear into the wall/floor leaving the basement and lost there. Checking outlets (switches/receptacles/luminaires) throughout the house indicated none were powered by the circuit.

Is the only option to start cutting holes in the wall and hope I can pick up the path of the cable run from there?

Would an analog tone and probe kit work? I guess I would switch off main breaker, pop the service panel, and hook up the probe directly to the start of the circuit within the panel, then chase the tone through the walls?

isherwood
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Jeremy W. Sherman
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2 Answers2

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Pick up a middle of the road tone generator and probe kit from a company you've heard of. No need to buy the most expensive model you can find, it will likely have features you'll never use.

I've used this one Gardner Bender Wire-Tracker Wire Tracer, which can be purchased from Home Depot for ~$40.00.

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It's not the best model on the market, but it worked very well for me. It was sensitive enough to accurately trace cables through both walls, ceilings and floors, and was able to attach to a variety of cables.

Make sure the power is off before connecting the tone generator. Some models can work on hot lines, but it's still safer to kill the power.

Tester101
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I plugged an old electrically noisy computer power supply in the outlet of interest and used a portable AM radio to detect which circuit breaker it was on. In my case, the nasty power supply was very noticeable around 550 KC.

So basically the AC filtering section capacitors are undoubtedly shot. I was listening to my radio one day in the kitchen area of my house when I came across the noise. It drove me crazy trying to locate the source. Turned out it was an old pentium computer running in my shop in the backyard.

Bill
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