This weekend I was doing a little electrical work at my house, which is probably the riskiest area of Do-It-Yourself home repair. You only need to cross a couple of live AC wires once and see the “pop” (and smell the ozone) before the point hits home.

In my case, I was installing a bunch of new light switches for a home automation project (dual-mode mesh network, if you care about those sorts of things). In the process I’m fixing some screwed up wiring installed by the builder; mostly three-way circuits they set up wrong.

I was getting ready to work on the only four-way in the house (that’s when you have 3 switches controlling one light) and cut the power at the circuit breaker. Each of the switches was in multi-gang boxes with other switches controlling other lights, so I had to kill all those circuits as well. From what I could tell, all the power was off and it was safe to work.

But being the paranoid that I am, I also checked with the AC indicator on my multimeter. I just press a button, wave it over a switch or outlet, and if it’s live the multimeter beeps.

And beep it did. Despite killing (I thought) all the lighting circuits for the first floor of my house, one switch was still hot. I then started the methodical process of hitting the rest of the breakers to find the right one.

About thirty minutes later I’d killed power to just about my entire house and still couldn’t find that damn circuit. Staring at my breakout panel (a second panel with the arc fault protection circuits for the bedrooms) I noticed two unlabeled breakers, figured out one of those was what I needed, and got back to work.

In this case my instincts told me the circuit was safe, but my detection tool dissolved that particular illusion. In other cases, especially with my crappy stud detector, my tools are often wrong and my instincts are right.

I guess it’s all a balancing act.

Now I just need to figure out how to get my alarm panel to stop beeping randomly at me. Something about losing power really pissed it off.