A subpanel is not necessary to ground separately, but a new SERVICE needs to be grounded separately. A subpanel runs off a circuit from the panel using whatever breaker/wire combination necessary to handle the amperage. But in Jay's case, if BOTH are 200 Amp circuits, well, there's no breaker big enough to do that job except in a new service panel, so probably Jay DOES need the second panel to be grounded to it's own ground point. It cannot be grounded to the original service's grounding point or tied back into that braid. -- Roger W. Norman SirMusic Studio Roger@SirMusicStudio.com 301-585-4681 "Scott Dorsey" <email@example.com> wrote in message news:firstname.lastname@example.org... > Jay Levitt <email@example.com> wrote: > > > >The ground itself is a thick braided cable, 3/0 gauge if I'm reading the > >smudged printing correctly. Oddly, I only see this cable going to one > >of the two panels, and one is NOT a sub-panel of the other; perhaps the > >ground is tied between them with regular Romex? These are 200-amp > >panels, FWIW. > > The code says that each individual service needs to be grounded, so that > second panel should have a connection to a ground. Pull the cover off > and look inside and see if it doesn't. > > It might be done with insulated wire, if the installing electrician had > some lying around, but that is not necessary or useful and costs more. > > >The other bad part is that the ground cable runs at LEAST 30 feet before > >disappearing into a crawlspace. That doesn't seem like a good thing. I > >suspect that this ground wire was not redone when the house was rewired, > >so it could be as old as 1970, when the house was first wired (it used > >to be a carriage house). Heck, it could be going nowhere at all > >anymore. > > The code says this is okay, as long as "the ground electrode is as near > as practicable to and preferably in the same area as the grounding conductor > connection to the system" (250-26C). > > >Interestingly, nothing in my studio seems to have been damaged. I > >assumed that was because of the Equitech isolation panel, but perhaps > >it's actually because the studio has its own ground rod, which is much > >more likely to be done correctly. That's all behind drywall, so I can't > >see where it goes. > > The isolation systems provide some isolation from trash on the power > lines, but they don't do anything about polluted grounds. > > Does the studio have a seperate service? If so, it should have an individual > ground. > > >My electrician's had a family emergency, but when he gets back to work, > >maybe he can shed some (battery-powered) light on the grounding system > >here. > > Go to the bookstore and get a copy of the NEC. It's lots of fun to try > and figure out. > --scott > > -- > "C'est un Nagra. C'est suisse, et tres, tres precis."