Recently, my wife found a great deal on a Skutt 41" oval kiln that a school had to get rid of. It had never been used, and they were offering it for $1200 (a great deal). So we borrowed a friend and a pickup truck and retrieved it. The next task was to wire it in. This particular kiln drew 50 amps at 240 volts and would require me to run special, low-gauge (very thick) wire and install a new breaker in the box. I'd done this previously for regular outlets and was only mildly terrified of the idea of opening my breaker box again.
So earlier this week, I began to pull the wire from one end of the basement to the other. Normally, this would take about 30 minutes, but this wire as bigger around than my thumb and weighed a ton. Drilling through the joists and securing it took most of an evening. Then I went to install the breaker. Except that there were no more holes in the breaker box through which to pull fresh wire. But I was game. I opened the breaker box (a 200 amp service) and began to loosen wire nuts to try to fit in this monstrous wire.
The smell of ozone was amazing. So was the sound. All the lights in the house went out. Somehow in removing a dead run that I'd earlier cut and safed off, I managed to trip the mains for the whole house. 200 amps worth of ozone. And I was about six inches from it. Oops. This is where everyone who reads this exclaims that I'm an idiot and should have killed the mains to start off with. But it was night, and I really didn't want to work by flashlight, and what's the worse that could happen, anyway? Yes, I'm an idiot.
My wife, ever patient, volunteered at that point to get a flash light since I needed to figure out what I'd done and whether it was wise to turn the mains back on. So she went to our emergency, earthquake kit in the basement to get the flashlight. Note to self: don't store the flashlight on the bottom of a 20-gallon crate of earthquake stuff. So she trundled upstairs in the dark to get the flashlight up there and returned after only about 10 minutes of me standing in the dark, knocking over power tools.
Work proceeded apace until I got to actually snapping the new breaker in. This is where I learned the difference between a 120/240 breaker and a straight 240 breaker. Seems that the latter was what I needed and the former was what I'd bought. Since a straight 240 breaker is 2" wide, and I was going to have to get one, I took this opportunity to actually make 2" of space for a new breaker by moving 25 breakers around. Our breaker box is now full.
The end of the story went well: the new kiln is now level and powered on. And I have to admit that I saved myself some money. And learned something. Namely that I should have hired an electrician in the first place.