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Old 04-15-2008, 08:16 PM   #1
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Grounding an Entire House


A friend of ours recently had a grouding rod installed for her entire house and she recommened that we do so as well. She thinks it will help protect her house if it is hit by lightening. I don't think having the house grounded will offer protection to the house if it is hit by lightening but I really don't know the purpose of having such a rod installed.

Can someone please explain this to me?

Thanks.

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Old 04-15-2008, 10:12 PM   #2
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Grounding an Entire House


All homes require a grounding electrode system called the GES. These electrodes are indeed for lightning protection and are for the benefit of saving your property from damage due to high voltage and amperage events like lightning and power surges like downed primary power lines energizing your house wiring.
Electrodes are generally in the form of your metal water pipe that supplies the house and ground rods that are supplemental to the metal water line. There are many types of electrodes that are permissible. The objective is to divert these high voltages and amperages to earth before they can damage property. earth in general is a poor conductor but high voltages that are associated with events like lightning can push amperage into the earth rather easily.

The vast majority of current in your house wiring returns to its source which is the serving utility transformer and does not travel to earth which is too resistive to current flow at the low voltages of residential utilities serving homes on the secondary side of the transformer.

On close inspection you will notice wires connected to your electrodes that originate at the service equipment and bond to the service neutral at the neutral bar in the panel.

The addition of a grounding electrode(s) would be required at todays standards if no other supplemental electrode is present.

In most homes the metal water pipe is your primary electrode and ground rods are supplemental to that.

This is a long subject so others may have some input so check back to this thread .

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Old 04-16-2008, 10:02 AM   #3
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Grounding an Entire House


I would like to add something to what Stubbie laid out. Another requirement in the National Electric code is that all ground rods on the premises be bonded (connected) together. So the rod for the telephone service, the rod for the satellite tv, the rod for the tv antenna, and the rods for any lightning protection system, must all be connected to the rods for the electric service. This bonding keeps all systems on the premises on an even electrical potential and helps prevent arcing and sparking during a lightning strike. In the country, the well casing is included in this bonding. In the city, as Stubbie mentioned, the water piping is used for this and no ground rods are needed.

I fried modems and surge suppressors on a regular basis until I dis-obeyed the telephone company, and bonded to their ground rods. I haven't had a problem since. And now they are finally complying with the electric code and permitting this bond. I live in the middle of an oak woods and lightning strikes are frequent at my house.

If you already have an acceptable grounding electrode system, which you most likely do, the addition of a ground rod is most likely a waste of time and money. If in doubt, have a licensed electrician look at your service.
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Old 04-16-2008, 10:17 AM   #4
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Grounding an Entire House


Thanks Stubbie and and jrclen for the replies. They do help me understand somewhat better.

However, based on this statement,
Quote:
If you already have an acceptable grounding electrode system, which you most likely do, the addition of a ground rod is most likely a waste of time and money. If in doubt, have a licensed electrician look at your service.
then our house, built in 1968, may have an "acceptable grounding electrode system."

I do know though, that in the kitchen and in one of the bathrooms, some of the original metal pipe has been replaced with PVC pipe. Does that constitute a break in the grounding electrode system?
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Old 04-16-2008, 10:38 AM   #5
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Grounding an Entire House


Are we talking electrical system grounding or installing a lightning rod system with it's own grounding?
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Old 04-16-2008, 11:16 AM   #6
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Grounding an Entire House


If the incoming water line was not disturbed and the bonding jumper is connected to the metal water line, the addition of some plastic pipe in the house will be of no concern.
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Old 04-16-2008, 11:52 AM   #7
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Grounding an Entire House


The previous posts are dead-on. Chances are, your house is safe, but it is worth checking. You often see "lightning rods" on top of homes and barns, which are separate of the electrical grounding system, but perform a similar function. Lightning will seek the easiest path to ground it can, and a lightning rod is pretty easy. Lightning rides outside the wire, and will often burn whatever the wire is in contact with (roof, framing, etc).

If your neighbor just added a grounding electrode (rod), where does he/she expect the lightning to hit? It still has to get to the grounding system inside the house somehow.
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Old 04-16-2008, 12:58 PM   #8
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Grounding an Entire House


Just one bit of caution before you go touching things. There is the possibilty of current on the grounding electode conductors that connect to your water pipe and rods. A few plumbers and electricians have paid dearly for faults that may be creating objectionable current flow on these grounding wires and metal floor drains, water pipes etc.. so just a heads up. Check for current before latching on to them.
Also if you choose to install a ground rod you need to install 2 of them unless you have the first one tested at 25 ohms or less.

And also very important on existing installations be darn sure you have all cables underground located before pounding in that ground rod. Nicking a hot conductor on a service lateral can ruin your day.....
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Old 04-16-2008, 09:48 PM   #9
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Originally Posted by Stubbie View Post
Also if you choose to install a ground rod you need to install 2 of them unless you have the first one tested at 25 ohms or less.
If there is an approved grounding electrode system already in place, there is no requirement for any rods. So no need for 2. There may be 2 already in place. Adding a third would be pretty pointless and a fourth would be bordering on silly.

I think the neighbor was sold a bill of goods by someone who is making money selling ground rods.
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Old 04-16-2008, 10:04 PM   #10
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Quote:
Originally Posted by dglockster View Post
However, based on this statement,

then our house, built in 1968, may have an "acceptable grounding electrode system."
All properly installed electric services do have an acceptable grounding electrode system. I have seen the wire damaged or removed from the ground rod or water pipe however. If in doubt hire an electrician to check it out.

Quote:
I do know though, that in the kitchen and in one of the bathrooms, some of the original metal pipe has been replaced with PVC pipe. Does that constitute a break in the grounding electrode system?
No problem with that. When the water pipe is used for the grounding electrode system, the connection is made very close to where the pipe enters the house. The pipe outside in the dirt is the grounding electrode. The pvc further inside the house will have no effect.
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Old 04-16-2008, 11:38 PM   #11
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Grounding an Entire House


Quote:
If there is an approved grounding electrode system already in place, there is no requirement for any rods. So no need for 2. There may be 2 already in place. Adding a third would be pretty pointless and a fourth would be bordering on silly.
I know a fellow electrician that drives 4 ground rods, sometimes he drives 8. He believes that doubling the ground rods halves the ground resistance. To each their own.

I agree with what you said I was assuming he didn't have any supplementary electrodes and if he chooses to have a rod he will need two.
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Old 04-17-2008, 09:29 AM   #12
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Quote:
Originally Posted by Stubbie View Post
I know a fellow electrician that drives 4 ground rods, sometimes he drives 8. He believes that doubling the ground rods halves the ground resistance. To each their own.

I agree with what you said I was assuming he didn't have any supplementary electrodes and if he chooses to have a rod he will need two.
Point well taken about the two rods Stubbie. 4 to 8 rods? Wow.

I wired a house last summer and ran into my first PVC well casing. I took a foot long chunk of #6 and a terminal and poked it into the ground to make it look like I had bonded to the PVC pipe. The inspector almost wet his pants laughing when he saw it. I wish I had taken a picture of it.

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