ECN Forum Forums General Topics of the Trade General Discussion Area 150 A Service

DS

I knew you were going to say that!

You're getting predictable.

Dspark,
the reason that the h2o is according to 250-66, and not allowed smaller is in the fact that a mettalic water pipe system IS the lowest impedance electrode usually avaliable.
( with Ufer's a close second)

the NEC does not, however, differentiate bettween a city system and an isolated residential system .

[This message has been edited by sparky (edited 06-05-2001).]

Sparky,

I believe that he knows that but is just in it for the argument.

In our area the Inspectors won't allow the second rod scenario unless it really is quite impossible to change the wire. Most areas here have gone to city water long ago. So the norm here would be older Metal Well casings/piping if any. Many times the GEC is still connected to the well and not the Water Main.


Bill

<I say that if you drive two rods 6' apart outside and bond to them, you don't have to
count the water main as an electrode requiring #4 copper. Indoor plumbing must be bonded, e.g., metal pipes, tanks, control boxes, and pumps.>

DS
The interior metal water piping system must be bonded with a conductor sized per Table 250-66. See 250-104(a)(1)
Don

The manufacturers put "value" packages together that include breakers. The one's I've seen are with 200 panels so that makes it easy to go with 200. Having said that, I would try to go with 150 if the present and future demands are minimal.

>I believe that he knows that but is just in it for the argument.

Wrong again. Like most people, I am here to learn. I think I asked a valid "why" question. And it has lead to another.

Why does the water line have to be used as an electrode? If some inspectors require this, that's fine. But does the NEC require this?

Because that water main is not a dedicated electrode and could be dug up and replaced with non-metallic, I prefer not to count it as an electrode. Instead, I use two rods bonded with #4. I don't expect anyone to dig up my ground rods and replace them with plastic.

Now I would like to know whether I should be using #4 for the water main or if #6 is okay even when the pipe has at least 10' in earth contact...

I think I have good questions. Naturally, I am going to try to defend my point of view. But that doesn't mean that I am looking for an argument. I am looking to learn the truth.

If the largest branch circuit that could energize the water main is 50 A, then I think that the existing #6 bonding it is adequate.

But of course you still must bond to the interior piping with a #4 at some readily accessible place(s).


[This message has been edited by Dspark (edited 06-05-2001).]

DS
>Why does the water line have to be used as an electrode? If some inspectors require this, that's fine. But does the NEC require this?
Yes the code does require the use of a metal underground water pipe as a grounding electrode if it exists. 250-50

>If the largest branch circuit that could energize the interior piping is 50 A, then I think that #6 bonding the interior piping is adequate.
Do you want to install what you think is correct, or what the code requires? If you were talking about other interior metal piping systems I would agree with your comment, but 250-104(a)(1) requires the bonding of an interior metal water piping system with a conductor sized per Table 250-66. If the undergound metal water pipe is used as a grounding electrode, then all that would be required to bond the interior piping would be a jumper at the water meter.
Don(resqcapt19)

>Do you want to install what you think is correct, or what the code requires?
I think I already stated that I want to know what the code requires.

I thank you for your response in that regard.

>the code does require the use of a metal underground water pipe as a grounding electrode if it exists. 250-50

I see what you are saying. I don't count it as a primary electrode for a number of reasons.

Please see http://www.nfpa.org/Codes/National_Electrical_CodeR__NEC/Proposals/necpdf/A250.PDF proposal 5- 152 - (250-50(a)) which was rejected. My thoughts follow along those of CMP member Schiff with respect to ground rods being primary and then bonding to the water line as opposed to utilizing the water line as a primary electrode.

I realize that some may think that the water line has to be a primary because of its low resistance, traditional use, etc.

However, because I can't prevent it from being removed and I neither check its resistance nor can I verify that it has at least 10 feet of metal in earth contact, I simply assume that I need two ground rods for my primary (permanent) electrode system.

Like CMPM Schiff, I am in the minority. But I am not just making an argument.

I am not 100% clear that Mr. Fletcher knew what he was saying. But in principle I agree with trying to reduce the current on the water line by bonding it to an alternative earth path.

DS
Even if you use the water pipe 2 ground rods are requires unless you can prove that a single rod complies with the 25 ohm rule in 250-56

At this time the code does. There are a number of reasons not to use the metal underground water piping system as a grounding electrode, but CMP5 has not yet agreed with those reasons.

The comments by Mr.Schiff about not using the metal underground piping as an electrode to improve safety of water department workers are not correct. If we stopped using it as the grounding electrode, but still bonded it to the grounding system inside the building the same safety problem will exist. The only way to improve safety for the water department workers would be to use a dielectric fitting in the water service to isolate the interior and exterior parts of the metal piping system. This is often done by gas utilities that are still using metal pipe for exterior gas supply lines.
Don(resqcapt19)