# Grounding electrode question



## Greg (Aug 1, 2007)

Art. 250.166 and Table 250.166 exception will cover your issue. The hand driven ground rods are supplemental and only needed to achieve 25 ohms or less. The UFER in the slab is a better ground than driven rods any day.


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## heel600 (Oct 31, 2007)

So I don't need the ground rods if I have the Ufer?


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## Greg (Aug 1, 2007)

Correct, but our inspectors don't understand grounding and still try to make us drive rods. So get ready for that discussion. If you have the test equipment to show 25 ohms or less it is a done deal.

Don't forget the water line. In Florida all of our water is in PVC or PEX.


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## JohnJ0906 (Jan 22, 2007)

Greg said:


> The hand driven ground rods are supplemental and only needed to achieve 25 ohms or less.


There is no NEC requirement for 25 ohms or less for grounding electrodes, except *single *ground rods, pipes, or plates - see 250.56






> The UFER in the slab is a better ground than driven rods any day.


Agreed.


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## workbook (Oct 28, 2008)

The Poco may require ground rods in spite of 250.50 and 250.52 in the code. They are very entrenched in old thinking and governed by Public Service Rules which may still require the rods. Just a thought.


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## electrician1957 (May 12, 2008)

On new houses I hit the UFER and Cold Water and that's it.


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## JohnJ0906 (Jan 22, 2007)

electrician1957 said:


> On new houses I hit the UFER and Cold Water and that's it.


I almost never see new houses with metal water pipe from the street anymore. It's usually PVC.


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## RePhase277 (Feb 5, 2008)

heel600 said:


> Just want to be doubly sure on this....
> 
> As long as I have one electrode (20' of 1/2" rebar in the footing) I do NOT need ground rods?
> 
> ...


If you have a water pipe electrode, it is required to be your primary, and then supplemented by another, not necessarily a rod. If you have a UFER, and a water pipe, then you are set.


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## TheRick (Apr 13, 2008)

heel600 said:


> I only need a ground rod if I were to use the water pipe, then the ground rod would be a required supplimental electrode, right?
> 
> Thanks!


 
250.50 tells you that if there is a water pipe, concrete encased electrode, and/or building steel available, you SHALL bond them ALL together to form the grounding electrode system. 

If only the water pipe is available then you must supplement it with one of the electrodes in 250.52(A)(2) through (A)(7).....it does not have to be a driven rod.

As always check with YOUR POCO and AHJ as they may have more stringent guidelines.


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## Effectively Grounded (Dec 15, 2008)

InPhase277 said:


> If you have a water pipe electrode, it is required to be your primary, and then supplemented by another, not necessarily a rod. If you have a UFER, and a water pipe, then you are set.


Wrong, wrong, wrong. Water pipe never has to be your primary, just bonded.


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## RePhase277 (Feb 5, 2008)

Effectively Grounded said:


> Wrong, wrong, wrong. Water pipe never has to be your primary, just bonded.


Well please enlighten me. I was under the impression that 250.50 and 250.52 were mandatory requirements, not optional.


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## Effectively Grounded (Dec 15, 2008)

InPhase277 said:


> Well please enlighten me. I was under the impression that 250.50 and 250.52 were mandatory requirements, not optional.


OK, I will enlighten you. Go back and read it yourself.

If you have a CEE then no other grounding means is necessary.

You still have to bond the metal water pipe, gas pipe, metal frame, etc. but the grounding electrode is the CEE and the GEC feeds only the CEE.

Show me where it says the water pipe has to be the primary. You can't because it does not.

The original post by heel is correct.


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## RePhase277 (Feb 5, 2008)

Effectively Grounded said:


> OK, I will enlighten you. Go back and read it yourself.
> 
> If you have a CEE then no other grounding means is necessary.
> 
> ...


I don't see where the code says that. It says that where there are multiple electrodes, they shall be bonded together to form the grounding electrode system. If there is a metal water line in contact with the earth for 10' or more, it is an electrode and the GEC must be sized to 250.66. In fact, I would argue that since the code specifically states that the GEC from a water line or building steel are to be sized by the table, yet the Ufer and ground ring and rod are not, it seems the intent is that water lines and building steel are primary electrodes.

I'll concede that the Code doesn't specifically label water lines as primary. But I believe that given they must be sized to the SECs, it is expected that they may carry a substantial current, more so than a rod or Ufer is expected to carry.

I'm not being difficult, just wanting to learn. What Code section references Ufers other than 250.52(A)(3), and 250.66(B)?


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## jwelectric (Sep 28, 2008)

Effectively Grounded said:


> OK, I will enlighten you. Go back and read it yourself. If you have a CEE then no other grounding means is necessary.


 I will agree if the concrete encased electrode is the only one present then it is all that is required by the NEC




Effectively Grounded said:


> You still have to bond the metal water pipe, gas pipe, metal frame, etc. but the grounding electrode is the CEE and the GEC feeds only the CEE.


 Again I will agree that a metal water pipe is to be bonded but if there is 10 or more feet in contact with earth then that part of the metal water pipe is an electrode and becomes part of the electrode system as well as the steel of the building. 

Once the steel of the building is bonded to the service then the steel of the building becomes part of the electrode system and the concrete encased electrode is not the sole electrode but is part of the system. In 250.52(A)(2) it states that the steel of a building that is connected to any of the other electrodes then becomes part of the electrode system itself. 

The Grounding Electrode Conductor could hit the building steel and a bonding jumper installed from the steel to the concrete encased electrode. If there is 10 feet of metal water pipe in contact with earth the Grounding Electrode Conductor could hit the water pipe and a bonding jumper installed from the water pipe to the concrete encased electrode. The concrete encased electrode does not have to be hit first.

It would also be compliant to install a Grounding Electrode Conductor to each of the electrodes independently. 




Effectively Grounded said:


> Show me where it says the water pipe has to be the primary. You can't because it does not.


 There is no such thing as a primary electrode. Any and all electrodes are to be bonded together to form one electrode system. 




Effectively Grounded said:


> The original post by heel is correct.


 I agree that if a concrete encased electrode is the only electrode present then this is all that needs to be hit. If there are more present then they must be bonded together to form the single electrode system


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## TheRick (Apr 13, 2008)

Effectively Grounded said:


> Show me where it says the water pipe has to be the primary.


 

:huh: Show me where the term Primary Grounding Electrode is used in the NEC???


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## RePhase277 (Feb 5, 2008)

TheRick said:


> :huh: Show me where the term Primary Grounding Electrode is used in the NEC???


Ok, that's my fault. The NEC doesn't say that a water line is the primary grounding electrode. But over 100 years of experience and study has shown that a metal water line electrode is superb. I believe the code makers knew this too, because for one thing it is #1 on the list. For another thing, the conductor that goes to a water line or building steel electrode has to be sized to the table 250.66. All the other electrodes, plates, pipes, rods, rings and Ufers have a "not required to be larger than"...

It seems the code makers thought that if a condition exists where an electrode carries current, then most of that would be carried by a water line or building steel. Primary electrodes.


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## jwelectric (Sep 28, 2008)

InPhase277 said:


> Ok, that's my fault. The NEC doesn't say that a water line is the primary grounding electrode. But over 100 years of experience and study has shown that a metal water line electrode is superb.


 Yes I would agree that in a city where all the underground water pipe is made of metal and tied to every electrical service the metal water pipe would make a very good electrode.
 Out in the county where the metal water pipe can be real short and not very deep it isn’t so good therefore it must be supplemented with another electrode such as rods. 





InPhase277 said:


> I believe the code makers knew this too, because for one thing it is #1 on the list.


 Well it is one of the oldest and something sure had to come first. 




InPhase277 said:


> For another thing, the conductor that goes to a water line or building steel electrode has to be sized to the table 250.66. All the other electrodes, plates, pipes, rods, rings and Ufers have a "not required to be larger than"...


 In the city where the metal water pipe could also be the grounded (neutral) it might be a good idea to make it at least as big as the grounded (neutral) conductor




InPhase277 said:


> It seems the code makers thought that if a condition exists where an electrode carries current, then most of that would be carried by a water line or building steel. Primary electrodes.


 Not primary just electrodes. There is no such thing as primary electrodes. There is only the electrode system. 

When looking at the rules outlined in the NEC we must look at the installations made nation wide not just what we are used to doing ourselves.


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## dognutz12 (Apr 30, 2008)

Since the NEC is somewhat fague on this issue the best advice I could offer is to do what I did. Contact your inspector to find out exactly what he or she requires. Our city inspector, who is very strict and sits on numerous comittees to rivise NEC and COMM, requires supplemental means (ground rods) only when copper water main is your primary. When a UFER is your primary, supplemental grounding means are not required. However, if the plumbing contractor uses copper pipe past the meter, you will still have to bond that system along with any other metal mechanical systems. (obviously)


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## TheRick (Apr 13, 2008)

dognutz12 said:


> Since the NEC is somewhat fague on this issue the best advice I could offer is to do what I did. Contact your inspector to find out exactly what he or she requires. Our city inspector, who is very strict and sits on numerous comittees to rivise NEC and COMM, requires supplemental means (ground rods) only when copper water main is your primary. When a UFER is your primary, supplemental grounding means are not required. However, if the plumbing contractor uses copper pipe past the meter, you will still have to bond that system along with any other metal mechanical systems. (obviously)


The NEC is actually quite clear on this subject, and what you describe as what your local inspector requires, is actually straight out of the NEC.


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