And here I thought I was hardcore taking my laptop on my front porch in the winter haha......the groud temperature should be more then enough to keep your system cool. You also have to take into account the ability of the groud to sink ALOT of heat.

Are you at all concerned about freezing air temperatures in the winter? It is getting into the single digits a few nights a year here in northern virginia (not sure what part you are in) so if there is a part of your piping that is exposed to air that should be a concern.