I recently installed a new receptacle and everything was ok. Used the receptacle tester after everything was closed up and everything was good.

I must have hastily put a cap on two joining ground wires in one of the junction boxes. It came loose and one of the wires popped out.

I was operating my air compressor and emptying the condensation out on the bottom using the relief valve when I got a nice jolt! Enough to scare the hell out of me! Put the tester on later and quickly found I had the open ground.

I guess a couple lessons learned here. Unplug the tools when you're done using them and don't be too careless when wiring things up!

 

Good lessons for all of us. To get this shock, you must have two faults: (1) an open ground and (2) a short between hot and the open ground.