Ground Electrode
Ground Electrode
(OP)
I have a site where a concrete foundation will be being poured for a new building. I had planned to connect to the re-bar with a bonding jumper in order to use the concrete as a grounding electrode. I have since found out that the foundation will be poured on a vapor barrier. My understanding of that is that it will no longer be a ground, which makes sense.
I plan to drive some ground rods and create a ground electrode for the building since the foundation is insulated from ground.
My question is there any value to tying a bonding jumper to the re-bar even though is is not a ground? Is there anything that can be done to ground the foundation? Is there value in tying the re-bar to the ground rods?
Thanks again,
Doug
I plan to drive some ground rods and create a ground electrode for the building since the foundation is insulated from ground.
My question is there any value to tying a bonding jumper to the re-bar even though is is not a ground? Is there anything that can be done to ground the foundation? Is there value in tying the re-bar to the ground rods?
Thanks again,
Doug





RE: Ground Electrode
The ground rod is needed regardless of the ufer ground. NEC article 250 covers how to bond everything together at the service.
RE: Ground Electrode
Can't remember but you can look it up
RE: Ground Electrode
I like the idea of tying to the re-bar and bringing the foundation to ground potential.
Yes 20' is the length that is required. However it can be re-bar or cable as long as it is encased in the concrete.
Thanks for the input.
RE: Ground Electrode
Our practice is to build- from the beginning- a layer of embedded rebar beneath the actual foundation and to connect this with the upper foundation rebar using a rebar of 1/2" dia through the vapor barrier. In any case you have to connect the foundation grounding to the nearby Grounding System. Note: the new NEC does not limit the minimum rebar diameter as for heavy short-circuit current 1/2" is not enough.IEEE-80 art.14.6 indicates how to calculate the required rebar size.
RE: Ground Electrode
Thanks,
Doug
RE: Ground Electrode
RE: Ground Electrode
It is not an option as NEC 250.50 requires that a metal underground water pipe be bonded to and used as a part of the grounding electrode system.
RE: Ground Electrode
RE: Ground Electrode
While I am not positive - I believe that rule of tying to water pipes may be changing - at least in this part of the world!
RE: Ground Electrode
You could install a separate concrete-encased grounding electrode that does meet NEC requirements, or drive a ground rod, or both. You can have as many grounding electrodes as you want.
You haven't mentioned the type or size of building, or the size of the electrical service. This could have an impact on grounding system design. The NEC is a minimum requirement, not necessarily the best engineering practice.
We always install a ground rod, no matter how good the ufer ground might be. It's cheap and will satisfy even the most brain-dead inspector. The NEC rules have changed over the years. Water-pipe grounds are still required for metal water pipes, but these are rapidly becoming extinct. I would never trust one as the sole grounding electrode even if metal pipe is used.
RE: Ground Electrode
Article 250.52 covers all of the acceptable grounding electrodes.
RE: Ground Electrode
The foundation grounding equalizes the potential throughout in a building reducing the touch potential and for short-circuit current to ground another path has to be created.
And as usual your posts are very interesting and very correct elaborated.
RE: Ground Electrode
RE: Ground Electrode
(A)Electrodes Permitted for Grounding.
(2)Metal Frame Electrode. The metal frame of a building/structure can serve as a grounding electrode when it meets at least one of the following conditions:
(1) At least one structural metal member is in direct contact with the earth for 10 ft or more, with or without concrete encasement.
RE: Ground Electrode
RE: Ground Electrode
RE: Ground Electrode
RE: Ground Electrode
RE: Ground Electrode
Bill
--------------------
"Why not the best?"
Jimmy Carter