I installed a new Whirlpool 50-Gallon Energy Smart Electric Water Heater EE2H50RD045V myself several months ago. I thought I did a good job installing it. Just my luck, after returning from a short vacation, I had no hot water. I found the circuit breaker had tripped. I noticed a burn hole in the plastic control panel of my water heater. With the power off, I removed the cover to find that one of the wire nuts melted and the wire (fortunately) shorted on the ground wire. About three inches of wire insulation melted away. I installed this unit so I figure I screwed something up. What might have happened?