Re: UFER
The Ufer ground relies on the building concrete as a sink for the GES (Grounding Electrode System). The Ufer ground is named after Mr. Ufer who developed it. If done right it is supposed to be a better ground than a driven ground rod. The alternative was for Ufer to drive ground rods hundreds of feet deep in the desert (due to the poor soil conductivity). Ufer ground was designed to run in the 5 Ohm range.
Ufer clamps (the clamp from the daylighted rebar to the copper jumper to the service entrance) must be rated for rebar. The Ufer must have at least 20 feet of continuity. It can be #4 rebar, or copper wire in footing:
NEC 250.52(A)(3), 250.70, 255.66(B), 250.24(A)(1), 250.56,
Here are links with more details. Post back with questions:
Google Ufer+ground
../Wayne C.
PS: In new construction assuming residential with a garage your service entrance might be at the front corner of the garage. Depending on who's doing it and what the AHJ says about the specifics here's what I used to do (I've been away from the trades for a while so keep in mind my methods are dated, dusty, and rusty): Take a 20' #4 rebar and bend a 90 degree bend in it about 2' long. Run the 18' towards the back of the garage footing, then stub the 2' section up into the wall right below the service entrance. Now there's only 18' of rebar in the concrete (20' min. required) so I would tie or clamp that rebar to the next rebar to extend the 18' onto the next piece. The fussy guy I am I would also make a good tight bond or use a clamp to tie this 20' section to a couple of the rebars coming up out of some pier holes. This gets the Ufer into some good damp concrete. It's probably unnecessary but it made me feel more like the Ufer was an earth ground. Pure a mental exercises, but I did it anyway. Finally you clamp onto the rebar stub with an approved clamp to jumper a piece of copper up into the N-G bus in the service entrance. Oh, and to make the clamp accessible I put a plaster ring on the garage wall if the wall is to be closed in by drywall. That way you can get to the clamp for inspection or to tighten it. Am I clear as mud? Post back with questions. Somebody probably has a picture that would alleviate these 1000 words of mine
[ September 10, 2003, 01:14 AM: Message edited by: awwt ]