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View Full Version : How many ground rods to install?



Washer Woman
09-01-2007, 03:21 PM
We are buillding a house and have come to the electrical part. We will have 200amp service and are running the ground wire from the disconnect we have to have because the panel isn't back-to-back with the meter. My question is simply how many ground rods do we need? I've heard between 2 & 8 and this will be the difference of a bit of change at $8.50 ea. So just wanted your all's thoughts. Location is in the hills of West Virginia, up on a hill but trees on two sides if the matters. A fair amount of lightening. Thanks so much

BrianJohn
09-01-2007, 03:48 PM
The NEC (National Electrical Code) requires one rod for if the tested reading for this one rod is below 25 ohms, they require a second rod a minimum seperation of 6 feet.

Drive two 8 foot rods, the best installation would have a minimum of 16 feet between them, twice the length of a single rod.

Are you planning on installing a lightning protection system, if so the LPS will have testing involved and minimum rods determined by this testing.

Lastly where in the Mountain State?

jwelectric
09-01-2007, 08:24 PM
If you donít know how many ground rods to install it might be a good idea to seek help with wiring the house instead of doing it yourself.

Washer Woman
09-02-2007, 04:44 AM
So how much should I pay a professional to come to the house with their ground rod(s), clamps, wire and beater and do exactly what I can do while I sit and watch? What a condescending reply. And I actually know what our electric company requires I was simply wanting to know if more would be better. Thanks BrianJones to you for your reply, the mountain state is east of Ohio and west of Virginia!

Cass
09-02-2007, 05:10 AM
The ground cable must be unbroken from the last ground rod to the panel reguardless of the number of ground rods, you can not use pieces, were you aware of that.

jwelectric was not being condescending, we do not know your level of knowledge, expertise and ability. You could do something wrong that could cost you loss of property or life.

He was being cautious and looking out for your safety by that comment.

seaneys
09-02-2007, 05:41 AM
Take a look at 'Wiring a House' by Cauldwell. He takes grounding very seriously. It is the first book I reach to when dealing with issues such as this. I still try to double check his book with the NEC, but thus far I have not found any contradictions.

Steve

Chris75
09-02-2007, 06:03 AM
Most areas require 2 rods, but feel free to pound in as many as you like...

BrianJohn
09-02-2007, 06:16 AM
Chris, if the area you live in follows the NEC two rods are not required if you follow the NEC and the results are less that 25 ohms, many/most electricians install two to avoid the hassle of testing.

More rods may minimize potential lightning damage if a comprehensive Lightning Protection System is installed.

I would consider installing a TVSS (Transient Voltage Surge Protection) at the Main Service.

WW I am familiar with WVA, I live on the border with WVA (Charlestown) and owned land there for years (Hrdy County), just curious about the nearest town/city.

I do not think JW was trying to be condescending it is an electrician thing, we feel only electricians can do OUR work....There are certain inherent dangers.

Chris75
09-02-2007, 06:35 AM
Chris, if the area you live in follows the NEC two rods are not required if you follow the NEC and the results are less that 25 ohms, many/most electricians install two to avoid the hassle of testing.




Exactly... too much work to get a ground rod tested, easier to just drive another rod...

BrianJohn
09-02-2007, 09:32 AM
True especially for residential projects, even then you may not meet 25 ohms, depending on time of year, location..etc......

Typically a 3 point test takes about 1-2 hours to perform properly, if you use an outside party to perform the testing (which many AHJs require) it runs about 350.00-650.00

Washer Woman
09-02-2007, 09:33 AM
Thank You all for your advice, BrianJones sorry, we are in Calhoun, it's nice to here from another WV person. The book that was mentioned by Cauldwell is actually the one that threw me when he says to put in eight rods. And we will be doing a surge arrester. Thanks again. Off to run cable.

sbrn33
09-04-2007, 06:26 AM
Do you have the rebar in the foundation grounded? This is far more important than a couple ground rods. If you have copper water line coming in and the concrete encased electrode(rebar) you may not even need ground rods.

hj
09-04-2007, 06:41 AM
You are building a house and a few $8.50 ground rods, if you needed more than two, would be a "deal breaker"? I tell people who are building houses that a $3,000.00 added expense is such a small percentage of the total project that it should be done if it makes the end result better.

BrianJohn
09-05-2007, 12:23 PM
HJ without doing some testing there is no proof that adding additional electrodes will buy you anything. In lousy soil conditions another 8' electrode can buy you .1 of an ohm.

Ufer ground electrodes have been shown to be an effective ground electrode in dry conditions due to the concrete retaining moisture. I have always wondered if there is any reports from damaged footers due to lighting strikes?

Lightning splits trees due to super heated sap exploding, concrete retains moisture the same damage is possible, I would assume?