50amp outlet in the garage

westend wrote:
I'd suggest to break out the hammer drill, drill a hole close to the load center you installed, and install a ground rod. Yeah, drilling through old barn floors and feed lot slabs can be tedious but a ground rod with short path to the load center is an ideal situation. If any device does short to ground, the length of the ground wire will be energized. A jacketed wire won't be too much of an issue but if the ground wire is bare copper, any flammable stuff on it may ignite.
It sounds like there was little thought to bringing any new service up to a reasonable state by the owner or past occupants. Now would be the time to get it as close to good as possible.

So long as ground and neutral are properly bonded together at the panel, a short to ground will trip the breaker and the ground will not stay energized.

Remember that the ground system serves two distinct (but somewhat related) purposes. It provides a low-impedance return path for fault current so that the current doesn't go through your fleshy bits. It also prevents the overall voltage of the system from floating to dangerously high levels above the local "ambient" voltage. The first purpose can be served without the overall system being grounded at all, so long as the ground and neutral systems are properly bonded together at the main panel. The second is what the lead to the ground rod is intended to do.

Particularly in a less than ideal electrical setup like this one, it would be a good idea IMHO to use a double-pole GFCI breaker for the RV outlet.