Today, in seeking to relocate the disconnect serving a ground-source heat pump, I got a mild shock. Almost a gentle tingle. I even felt this from the neutral, as well as the hot lines (on the line side).
I suspect the ground source heat pump is providing a different ground than the utility ground.
Remember lightning strikes taking out well pumps due to the casing being a better ground electrode.
I suspect the heat pump heat collectors are better grounds than the service earth electrode.
