"Wayne Whitney" wrote in message
...
Hello,

I'm having my foundation replaced here in California, and I'm
wondering about opportunities to improve my ground electrode system
before the concrete is poured. The foundation is engineered and has
alot of rebar, and the foundation contractor has installed a 20 foot
length of copper wire in the foundation. I assume this is tied to the
rebar and will double check.

Is this sufficient? The foundation consists of about 100' of stem
wall with a footing about 3' deep, about 100' of retaining wall with a
footing 6' deep, and a concrete slab of 450 square feet about 4' below
grade. The surrounding soil is clay. I assume that I should insure
that the rebar of the various elements (stem wall, retaining wall and
slab) are electrically connected? Are there any other measures I
should take, like a grounding rod below the slab?

On a related question, if my main panel and my service disconnecting
means are separate, should the grounding electrode system tie in at
one or the other or both?

Thanks,
Wayne

The 20 feet of usually #4 bare solid copper is the minimum for a ufer
ground. Used mostly in the western US. I have installed 40' of larger
conductor and gotten minimal improvement. It really depends on the soil
resistivitiy. There are meters that can provide the readings or you could
hire someone to do it for you.
I would suggest to you that you allow the installation as is and then after
the fact drive a ground rod more than 10 feet way from the foundation and
connect that as well to your service. Connect the ground rod with #4 buried
in the ground. Here in AZ your required to use a ufer. On a service change
you must drive 2 ground rods or provide documentation that you have achieved
25 ohms or less. Driving 2 rods is way cheaper than providing the
documentation. Amec makes a cool meter that measures grounds with out
taking them out of service. Check ww grainger about 2k.

If your interested performance grounding starts out at less than 10 ohms and
some specify less than 5.

The electrical service is where the neutral, grounded conductor is
established. A separate ground wire of the proper size should be run from
the service to the panel. Assuming your a typical residential service that
would mean 2 hots a neutral and a ground.