here is the problom. in an old building that we work in there is a 200a sub panel. It is being feed w/ 3 hot conductors (120/208) there is no grounded or grounding conductors w/ the feed. Coming off the sub panal to a water pipe is a number 10awg, it is terminated under a ground clamp. this number 10 is being used as both the gounded and the grounding conductor. this sub panel feeds a/c units as well as sensitive sound equipment(which periodically hums and buzzes). HOw do i explain to the customer the proploms here and what exactly are my probloms?