I was working installing a 2 pole 50A 240V GFCI breaker and trying to debug an appliance. I turned off the GFCI breaker I was working on, but the main breaker was on. About the time I had one of the wires undone I put my hand on the metal enclosure of the breaker box and received a shock. What could possibly have caused this? The main was on, and the GFCI breaker was connected to the box via the pigtail to the neutral terminal. Any heuristics/diagnostics to determine why the external enclosure became electrified?
The subpanel (in a detached garage) has 4 wires coming in: 2 hot to the main breaker, one to the grounding bus, and neutral to the neutral bus. In addition, there is a very thick copper wire running outside the conduit that appears to terminate in the ground below the deck on the outside of the building.
There is continuity between the neutral and ground bus, which I understand is not normal for a subpanel.
Am I right in suspecting that the grounding electrode is not grounded? How would I test this?