first, what constitutes a "detached" building? my garage (and a small guest apt) is physically attached via a breezeway of nearly 20'. is it, by NEC definition, a detached or an attached building?
the garage has a subpanel fed by a 3-wire cable (2 hot, 1 gnd) which, in turn, is connected to the main subpanel in the house. from the discussion in a previous thread this seems to be legal prior to the 2008 NEC *if* the garage is a detached structure. however, i question the fact that the gnd of the cable is connected at the main subpanel rather than at the main panel itself. i think it should be ok but what say you?
fwiw, the house was build in the late '50s. thanks