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Old 05-11-2008, 12:09 PM   #1
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Grounded electrode on water pipe


I'm just trying to satisfy my curiosity; and or lack of knowledge on, or about these matters. I hope this isn't a dump question; I'm just trying to connect the dots.

What is the significance; or the net affect to the grounded conductor system; when the function of one or both of the existing grounded electrodes are canceled out in some manner.
The first grounded electrode is clamped to the inside water pipe within five feet of the inside building wall; but its intended function is canceled out by the presence of a 4" rubber joint connection on the water pipe at the building wall. There is no jumper around the rubber joint/ connection.
There is a second ground wire (grounded electrode), which leaves the building next to the main panel at the point where the feeder enters the building.

So, what if that second ground wire does not connect to a 10' ground rod outside as it is supposed too. Say it only has a few feet of wire buried a few feet deep. All together what would be the cumulative affect of such a scenario to the grounded conductor system.

If there is a ground rod outside, it is buried to wit nothing is showing. In the next week or so; I intend to dig around out there and investigate; because I question whether the ground rod exists at all. Is this even important.

If I understand correctly the grounded/ bonded electrode system facilitates the flow of unbalanced current back to center pole tap. I understand as Stubbie has pointed out that one of the functions of the grounded/ bonded electrode system is to protect the equipment in cases such as a lightning strike.
In addition to having a lack of protection in such a catastrophic event; I'm wondering what negative effect this scenario has on the overall function of the grounded conductor system. I could make a guess, but I would rather hear your opinions.

In another thread Stubbie mentions this;
Quote:
Equipment ground and neutrals and grounded legs join up at the service equipment (main panel in your case) because both must use the service neutral for their currents to get back to the center tap of the transformer. In other words in your case you have a two lane road merging at the neutral bar(s) of the service equipment and then a one lane road (service neutral) that they both share to return to the source center tap.
Thanks, to all you guys for the time you give, and everything.

Thanks T.


Last edited by TW Lucas; 05-11-2008 at 12:11 PM.
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Old 05-11-2008, 12:20 PM   #2
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Grounded electrode on water pipe


What exactly do you want to know? Why we have certain types of Grounding Electrode systems? Try reading 250.50 in the NEC, Basically if certain things exist at the structure than we MUST use them as Grounding Electrodes.

To answer your first question, we install/ use existing Grounding Electrodes to limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines.


Here is a picture of the available Grounding Electrodes, In most houses I do, I only have two ground rods, and thats perfectly fine. BUT if the others exist, then I MUST use them, in other words, they have to be bonded together.
Name:  250.50.jpg
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Last edited by chris75; 05-11-2008 at 12:31 PM.
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Old 05-11-2008, 09:25 PM   #3
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Grounded electrode on water pipe


Quote:
Originally Posted by TW Lucas View Post
So, what if that second ground wire does not connect to a 10' ground rod outside as it is supposed too. Say it only has a few feet of wire buried a few feet deep.

If there is a ground rod outside, it is buried to wit nothing is showing. In the next week or so; I intend to dig around out there and investigate; because I question whether the ground rod exists at all. Is this even important.
The rod is supposed to be buried which means that the connection to the rod is buried as well. Perhaps you have seen several installations where the rod protrudes above ground? This can indicate poor installation.

In my juristiction, it is customary to drive the rod below the soil, make the connection and leave the final product visible to the inspector. Usually, you leave a pile of soil next to the hole which the inspector (sometimes) kicks in when he has seen the rod/connection and is happy.

I would expect that you'll find the rod and the clamp if you go digging. If you don't, DON'T FREAK! (at least initially). We can help if that is the problem. On the other hand, if you give the grounding electrode conductor a good tug and it doesn't just pop out of the ground, chances are that it is connected to something and more than likely it is the ground rod.

Quote:
Originally Posted by TW Lucas View Post
If I understand correctly the grounded/ bonded electrode system facilitates the flow of unbalanced current back to center pole tap.
First of all, grounding and bonding are different terms and often people use them (incorrectly) interchangeably. The "grounding electrode system" is required to dissipate lightning strikes and the like.

Notice the small and seeminly innocuous difference between grounded and grounding conductors? The grounded conductor is typically the neutral which carried current under normal conditions (look in your main panel. The neutrals are terminated on a bus which is connected to ground). The grounding conductor only carries fault current, i.e. during a short circuit.

With respect to the "grounding electrode system" carrying the imbalance, the answer is "No." The neutral from the distribution system is what returns normal and fault current to the source (i.e. pole- or pad-mounted distribution transformers, assuming a US system). If you have a service drop, you'll notice two insulated cables twisted on a bare cable. That bare cable serves as both a messenger to support the others and as the neutral. It is not insulated as it is grounded and does not need to be (insulated). In your panel though, you'd typically see three insulated cables coming in, one of which should be marked with white tape.

The only times that a "grounded" conductor carries imbalance current is with multi-wire brance circuits and 3-phase, 4-wire Y-connected feeders.
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Old 05-12-2008, 12:10 AM   #4
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Grounded electrode on water pipe


Thanks for your replies,
I could have simply asked, whether the rubber fitting on the water pipe would defeat the function of the grounded electrode, creating an unsafe condition?

I suppose my ego made me add all of the other details as though I were piecing together some great mystery. I did a google search on the NEC 250.50 code and read a couple of articles on the subject.

I do follow the different roles the grounding system, and grounded conductor play. I was jumping to conclusions, and over simplified the relationship between them.

I apologize for my long winded question; and I thank you for your help.
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Old 05-12-2008, 05:40 AM   #5
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Grounded electrode on water pipe


Quote:
Originally Posted by TW Lucas View Post
Thanks for your replies,
I could have simply asked, whether the rubber fitting on the water pipe would defeat the function of the grounded electrode, creating an unsafe condition?
You would just install a jumper wire. As far as unsafe? Depends on the situation. In normal everyday use, not at all. A electrical system does not require a Grounding Electrode system to function.
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Old 05-12-2008, 09:31 AM   #6
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Grounded electrode on water pipe


Hello Chis75,
I realize now that the rubber joint which interrupts the grounding electrodes path probably does not create an unsafe condition. Though it may be violate of nec 250.68 as it stands.

The rubber joint is tight against the wall where the water enters the house; so there is no way to jumper around it. I suppose the water pipe is required to be grounded anyway; but it is also connected to the other ground wire at the main panel which exits the house at that point.
Thanks,
T.
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Old 05-12-2008, 09:33 AM   #7
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Grounded electrode on water pipe


Back to the grounding electrode/rod that you were concerned about. Here's an excerpt from the 2005 NEC:


(G) Rod and Pipe Electrodes.
The electrode shall be installed

such that at least 2.44 m (8 ft) of length is in contact
with the soil. It shall be driven to a depth of not less than 2.44 m (8 ft) except that, where rock bottom is encountered, the electrode shall be driven at an oblique angle not to exceed 45 degrees from the vertical or, where rock bottom is encountered at an angle up to 45 degrees, the electrode shall be permitted to be buried in a trench that is at least 750 mm (30 in.) deep. The upper end of the electrode shall be flush
with or below ground level unless the aboveground end and
the grounding electrode conductor attachment are protected against physical damage as specified in 250.10.


(The code uses the term "electrode" since a rod is not the only type you are allowed to use.)

So, for an 8ft. ground rod, you shouldn't see the rod poking up out of the ground. Even for a longer rod, the last part of this item requires that the rod be flush or below ground. I'm guessing that a lot of the rods that I see are not necessarily installed correctly because I can see them!

Chris gives some good, practical advice here. Just remember: The grounding system does not conduct current under normal conditions. It's basically there to protect people in the event of a lightning strike.

Take care,
Jimmy
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Old 05-12-2008, 11:33 AM   #8
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Grounded electrode on water pipe


Hello Jimmy,
I really appreciate all the helpful information provided by you guys. I spent last month studying chess; and learning Spanish on line; this seems a lot more interesting. It hits closer to home.
Quote:
I'm guessing that a lot of the rods that I see are not necessarily installed correctly because I can see them!
That is probably where I got the idea. I've located utilities for 13 years, and I've seen a few of those ground rods sticking out of the ground. The cable company and phone company often clamp their cable drops to them.
Come to think of it; a few times in almost new developments, I've seen that ground wire coming out of the house by the meter, hanging in mid air two feet off the ground. I imagine thats a whole other can of worms!
T.


Last edited by TW Lucas; 05-12-2008 at 11:49 AM.
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