>I like the idea of multiple grounds but most experts recomend one and only one ground point to avoid large ground currents in storms. Perhaps the important part of that scheme is to make the tie point at the panel? Yes that is the point, and in fact it is required by code to be wired as a single point ground. You may in fact have potential between two of the tie points, but the juice will be traveling along a big thick copper ground wire between these points, not through your power system. However, ground bounce is real and there could be an issue. Some commercial systems go so far as to bury a bare copper cable in a ring all the way around the building, IN ADDITION to these other methods. I've never specified that, though. This may be needed where soil conditions make ground rods useless. In my reading on this subject, rebar in concrete in contact with soil was the absolute lowest ground resistance you could get. The ability of a 1/2" diameter steel rod to handle mega-currents is tremendous. I doubt you'd have any spalling of concrete even with a direct strike. Just anything within 10 feet would be fried. -- Lawrence Lile Senior Project Engineer Toastmaster, Inc. Division of Salton, Inc. 573-446-5661 voice 573-446-5676 fax John Ferrell Sent by: pic microcontroller discussion list 08/27/2003 08:06 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: Re: [EE:] Relocating house earth ground A couple of items: It sounds like your specs passed inspection, so you must be right. I have been concerned about trying to ground a lightning strike through rebar, it seems to me the concrete could erupt with violence. I like the idea of multiple grounds but most experts recomend one and only one ground point to avoid large ground currents in storms. Perhaps the important part of that scheme is to make the tie point at the panel? John Ferrell 6241 Phillippi Rd Julian NC 27283 Phone: (336)685-9606 johnferrell@earthlink.net Dixie Competition Products NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" ----- Original Message ----- From: To: Sent: Wednesday, August 27, 2003 12:49 PM Subject: Re: [EE:] Relocating house earth ground > In my NEW house, if I ever get started building it anyway, there will be a > piece of rebar sticking out of the floor under the panelboard. This rebar > will be tied to the other rebar in the slab, not just stuck into the > concrete. Yeah, I will put a silly wire to a ridiculous rod in the ground > to make the inspector happy, but the real ground will be to the rebar. > When I used to specify commercial panelboards, the prefferred ground was > either a rebar sticking out of a concrete slab, or a cadweld onto a handy > steel beam. Or both. I would usually specify at least 3 different > connections to steel and concrete all coming to a single point at the main > panelboard. Rebar in concrete has a far lower resistance than a copper > rod driven into dry ground. BTW these methods are all recognized by NEC > code. > > > > -- Lawrence Lile > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body