About 2 years ago, my neighbor asked me to look at a new sink disposal installation that was performed by a plumbing contractor, not some jackleg.
The problem is that when she flipped the wall switch, it would spark and trip the breaker. When she confronted the installation technician about the electrical problem, late in the afternoon, his response was " I can't fix it. I'm not an Electrician". At the time, her husband (a Civil Engineer) was out of town, not due back until the next day.
When I got there, I noticed that the disposal was mounted and piped correctly. However, the
Professional Installation Technician wired the
motor wires together and the
supply hot to neutral. Also, he didn't install a separate ground. The wall switch that operated the disposal had exploded.
I took a picture of the botched wiring job (see below), disconnected any unsafe wiring, and sent the picture to her husband. I figured that he could take appropriate action. Unfortunately, he couldn't get anywhere with the contractor.
Assuming that he's a Civil Engineer, he would know where to get the best bang for the buck, if he had to file a complaint at the county office for contractor's licenses.
I came back, corrected the wiring and installed a heavier switch in the wall. I don't know if the plumbing contractor made right or not.