How a 5-minute circuit scan saved me hundreds (and exposed a serious wiring surprise)

ZDNET's key takeaways

• The Klein Tools 80016 Circuit Breaker Finder effectively maps circuits throughout your home.
• It's a useful tool with clear discovery indicators and improved safety features.
• It's somewhat pricey at $65, with minimal directions for beginners.

Do you ever wonder what wall socket corresponds to which circuit breaker or circuit in your main electrical panel? Do you ever wonder how much current a particular socket can handle? I did. I found a cool tool in the Klein 80016 Circuit Breaker Finder that helped me answer those questions. It can help you, too.

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Here's my story. It starts with a mystery, grows into a bafflement, and eventually results in something better than I could have possibly hoped for. But that's the luck of the draw. Going in, I had no idea.

This is the Fab Lab. It's a narrow 8x14-foot room that contains my non-messy desktop fabrication gear. I divide up my fabrication gear into messy (the CNC, resin 3D printers, cutters and saws, etc.) and non-messy (servers, 3D printers, the Glowforge, microscope, etc).

David Gewirtz/ZDNET

The messy stuff lives in my workshop, which I can also vent to the outside by opening the garage door. The non-messy stuff lives in the Fab Lab, which does have a vent for the Glowforge but is otherwise nicely climate-controlled. Both servers and 3D printers like climate control.

The problem with the Fab Lab

That narrow room, the Fab Lab, has six wall sockets. I wanted to find out how much power was going into the room because it supports four servers, seven 3D printers, and a laser cutter. I was concerned about trying to run it all on one 15A circuit, which is not enough juice for all that gear to run at once.

Unfortunately, I had no idea what wall socket went to what circuit. This is an odd house, built up incrementally over the years, with each subsequent owner making homeowner-style hacks to everything. None of the labels in the breaker box could be directly mapped to the small room holding my 3D printers.

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I planned to call my electrician to see if he could add some circuits, but first, I wanted to know what I had. I tried the age-old trick of turning on and off breakers and yelling across the house to my wife, but the accuracy of that practice left something to be desired.

So I bought a tool. I always love it when an actual need justifies buying a new tool. I don't buy tools just to have them. I wait until I need something. When I actually have a legitimate need for something cool and different, that's a cause for celebration. Hey, you get your joy your way. I'll get it my way. Don't even get me started on my love of charts and diagrams.

So, yeah, I bought the tool and made a diagram.

Enter the circuit breaker finder

The tool in question is the Klein Tools 80016 Circuit Breaker Finder. It has two parts. The first is something that looks like a socket tester. It plugs into the wall socket, and indicates if the circuit is good via some lights on the small device.

To find the right circuit in the electrical panel, you first plug the socket tester into a socket. Then you go to the panel and slide the probe up and down all the breakers. You then do a complete cycle of all the breakers, ignoring any sounds. This allows the device to set a baseline.

David Gewirtz/ZDNET

After that, you move the device breaker-by-breaker until you hear a tone. The breaker you're touching when you hear the tone is the breaker that corresponds with the socket.

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I did this with all six of my sockets, fully expecting them all to correspond with a single 15-amp breaker somewhere in the panel.

What I found gave me the… figurative… shock of my life.

Well, that was unexpected

What I found was that there were four 20-amp circuits feeding those six sockets. Three of the sockets had their own full 20-amp circuits; three other sockets shared the one remaining 20-amp circuit.

I discovered one more thing that turned the weird up another notch. There's one socket on the left wall that provides power to my four servers and four 3D printers. I traced that back to a circuit breaker in the panel, which was labeled MB Lights, for master bathroom lights.

So, yeah, the circuit that was handling all my servers and four printers is the same circuit that provides power to part of the bathroom. Fortunately, the load coming from the bathroom (wow, that does not sound right!) is minimal. It's only a few ceiling bulbs.

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In the end (that doesn't sound right either), I had the electrician use conduit to extend one of the other circuits to that same wall. That way, I could isolate the servers to the circuit shared with the bathroom lights, and put the four 3D printers on their own circuit.

I put the Glowforge on its own circuit. The three remaining 3D printers on the right wall all now share their own 20 amp circuit.

ZDNET's buying advice

The fact is, without the Klein circuit finding gadget, I never would have known that I already had more than enough power going into the Fab Lab. I would have assumed that I was working with the one 15 amp circuit that such a room normally is allocated. I would have never allowed myself to run all my gear at the same time. 

But now that I have my circuits identified and properly allocated, I can keep all my printers running, which can be a huge time saver for a big job.

What about you? Have you ever tried to map your home's wall sockets to their circuit breakers? Have you used a circuit finder or relied on trial and error? Do you think your workspace is getting the power it needs, or are you just hoping for the best? Let us know in the comments below.

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