i have a few questions about the grounding system in a house. ok here goes. can anyone tell me about ground rods and where they need to be set and where they come from .basically im asking some one to explain the whole grounding system to me any help would be appreciated. thanks
Jayson - this topic is FAR too complex for anyone to give you an 'in-a-nutshell' explanation on this topic. There are many of us who have studied this subject for years and are still learning everyday. I strongly recommend you buy Mike Holt's "Grounding & Bonding" book on this subject - it is color illustrated, takes you through Art. 250 and is as clearly written as possible for this subject. I think most people come away feeling it is a very understandable and 'user-friendly' text on the subject....$30
#89445 - 09/16/0402:49 AMRe: residential ground system
You need two ground rods set at least 6 feet apart. You could get by with one, but you would have to perform a test that takes time and a fairly expensive piece of equipment. Trouble is, there are very few places in this country where one ground rod would pass the test, so you'll likely end up pounding in the second rod anyhow.
Few things are harder to put up with than the annoyance of a good example.
#89449 - 09/16/0406:05 PMRe: residential ground system
I understand NEC says 6 feet minimum between ground rods. I attended a grounding seminar where we were told that rods should be 2X rod length apart. Right now I don't remember the term for why 2X is best but it had to do with dissipation.
#89451 - 09/16/0410:28 PMRe: residential ground system
They call it "the well of influence" and it is a circle the size of the rod depth as a radius. If you have 2 sharing the same well they are only getting the benefit of one rod. Someone decided that a 2 foot overlap on an 8' radius was the point where you were losing enough grounding ability that you should stop the bleeding and they made that the minimum. The reason we get the pitch in seminars is for those times when we are not trying to do the "minimum" and we are driving deeper rods. At that point you also want to spread out accordingly. Using the same logic the minimum distance should be 75% of rod length, up to 200% when the wells don't touch. When you are really serious about grounding you will be running several of these rods in a circle with a ground ring between them and long "radials" back to the center of your grounding system, usually a radio tower with a Ufer ground in the radio shack. The radials will also extend out from the ring quite a ways to make your ground plane bigger. The only other thing I have worked with that gets grounded like that is a toll plaza.
[This message has been edited by gfretwell (edited 09-16-2004).]
#89452 - 09/17/0406:07 PMRe: residential ground system