When I worked in the cabinet shop I was the go-to guy for anything electrical. This one lady who was making minimum doing busywork all day kept making a lot of noise about how she was experienced at electrical work and had "wired 3 prisons down south" as an "apprentice electrician". No one really believed her except the VP of the company got her ear bent by Barb one day. She comes to me and the shop foreman with "Did you know that Barb is an electrician? She should be wiring these cabinets. We can't afford any mistakes." to which the foreman responded something like "Well, if it's electrical and I want it done right the first time, I ask [me] to do it." Her response was colorful and included the term "misogynistic" and neeedless to say, she got her way.
So Barb sets about wiring her first cabinet. It had a plexiglas window in the front, around which was to be mounted 6 24" 2-tube fluorescent fixtures on the inside of the cabinet so that when you looked in the window, the interior was illuminated but you couldn't see the lights. There was to be a switch on the back side of the cabinet to turn the lights on and off. I stayed away all day until the foreman called me over for the unveiling about 6 hours later. "You're going to like this," he said "I've been watching her."
So Barb goes and plugs in the power cord to a receptacle and the cabinet illuminates with a beautiful light. The few people who were watching murmured their approval, and the VP who had come out to the shop floor gave a little thumbs up. Then Barb throws the switch and the lights turn off. The foreman (who had a degree in electrical engineering) starts chuckling and says "Hey Barb, turn that back on a second." It was about this time that I notice one of the guys was looking with puzzlement at a nearby table saw as he flipped the switch back and forth, a half-ripped board in his other hand. Barb throws the switch again to no effect as the guy at the saw calls out "Did we lose power or trip a breaker or something?"
To make along story longer, Barb had zero experience with anything electrical. She had worked for an electrician on the "prisons down south", but her duties were limited to screwing down conduit and assisting in wire pulls. The foreman instructed me to open the cabinet and correct whatever she had done, which was:
Each of the six lights had a a wire whip coming from the ballast box of 12/3 appliance cable (like for make-your-own extension cords and stuff) which she got of a spool in the electrical department. The lights were not daisy-chained together even though they formed a shape like a oval. There was just a cable going from each light. All the cables stretched back to a single junction box in the corner of the cabinet. Also entering this junction box was a cable coming from the switch box and the power cable. Inside the light boxes, she had connected the green wire from the cable to the grounding screw, and connected the white from the cable to the white from the ballast, and the black from the cable to the black from the ballast. Not too shabby, aside from the god-awful cable routing. Inside the switch box she had connected the green wire to the grounding screw on the switch, and connected the black wire to one side and the white wire to the other side of the switch. Ok, this could work, depending on how things were in that main junction box. . . .
Inside the junction box were 6 cables coming from lights, one power cable and one cable from the switch box.
All the green wires were cut off flush with the sheath.
All the white wires were nutted together with a giant wire nut
All the black wires were nutted together with a giant wire nut
So basically, the only reason it lit up at all was because the switch was off when she plugged it in. As soon as she flipped the switch (to "ON"), she closed a dead short between the neutral and hot, tripping the breaker.