grounding

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  #1  
Old 03-24-06, 04:49 AM
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grounding

Seems to be a difference of opinion on how to ground an electric service where you have to use two ground rods.A continuous loop from the breaker panel out to the two rods and back to the panel or just a continuous run between the two rods and then to the breaker panel. Which is right? Also where do I find this ruling in the NEC. Thanks
 
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Old 03-24-06, 05:58 AM
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The prefered method is to run the grounding conductor from the panel to the first rod, then the second. NEC 250.64 (F) is as close as the "method" is described, however there is NO reference to a loop back to the panel. You should know that the NEC is a document that is written so that if something isn't detailed as required, it isn't. Since the purpose of the grounding electrodes is to channel things like lightning to ground, a single path that is as short as possible is prefered

I've been in the business 30+ years and I've never heard of looping the wire back to the panel from the second ground rod. Where's this coming from?
 
  #3  
Old 03-24-06, 10:18 AM
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I have never heard of looping back either.
In Mass. we can run from the rods to the meter socket and bond with the neutral there.
Or put the rods inside the basement(pre construction). But we must always ground the water and jump the water meter, and this goes back to the panel.
 
  #4  
Old 03-24-06, 01:30 PM
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Originally Posted by bern
A continuous loop from the breaker panel out to the two rods
Actually, a continuous (no splices) wire is preferred.
A loop would be redundant.
 
  #5  
Old 04-26-06, 01:49 PM
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Distance?

I am trying to learn a little about grounding rods...
Is there a limit in distance between the panel and your first grounding rod? If so, what is the maximum number of feet?
Thanks!
Howie
 
  #6  
Old 04-26-06, 03:36 PM
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When you use 2 ground rods for an application for a service entrance you would go from your meter pan to the 2 ground rods continuously. Remember to keep your distance between the two rods at least 6'ft apart, I prefer to keep the grounds close to service entrance. Next you would go from your ground bar from panel to the cold water pipe, usually where your water main cutoff valve is located in the front or side. I don't know about in other states but in nola they want a cold water pipe that's embedded 10' in the concrete. I'm not sure about the max. distance apart grounds should be. My rule of thumb is anything over 10' , I use another ground rod. I've gone as far as putting 8 ground rods to a house .
 
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Old 04-26-06, 05:34 PM
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Originally Posted by jamead65
I've gone as far as putting 8 ground rods to a house .
May I ask why??



Bern,
Remember, in many areas, mine included, we do NOT go to the meter pan with the GEC (grounding electrode conductor). We come from the grounded bar in the main panel. The POCO does NOT want the GEC in their (your) sealed meter pan.

There is NO max distance to the ground rods from the service. As close as possible is common sense.
 
  #8  
Old 04-26-06, 06:36 PM
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QUOTE=Speedy Petey]May I ask why??
I had this house in New Orleans, Lakeview area that was huge.
It must have been at least 6000 to 8000 sq.ft.. The service was a 120/240V 400amp feed. I had parralleled my feeds from the pole. From the meter pan I used two 200amp 44space panels . I've could've used 2-rods and been fine, but the with the swimming pool and all the pumps and motors and the fact that this guy had 4 kids 3mo. and up to 6 I wanted this house safe so I used 8 rods approx. 10ft .
 
  #9  
Old 04-26-06, 07:26 PM
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more is better: a ground rod every 6'

> I could've used 2 rods and been fine
Either it would have been or not.

Or did you mean that you would be fine, but the kids wouldn't be?

> I wanted this house safe
Safe from what?

You mentioned kids and pool. Grounding rods are not a substitute for parental/adult supervision.

Kids get older, new ones are born, another family moves into the house. And what about animal companions? No one wants Fido fried.

So I would like to know how to install ground rods to make houses safe for kids.
 
  #10  
Old 04-26-06, 07:57 PM
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WoW

Wow! you're smart.
 
  #11  
Old 04-26-06, 08:22 PM
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jmead65,

I too am curious as to the specific issue that you were solving through the use of additional ground rods.

Code requires one ground rod if the ground resistance is less than 25 ohms, but permits 2 ground rods to be used in lieu of testing. Did you actually test grounding electrode resistance?

You mention a pool. Did you bond to the pool re-bar or otherwise create an equipotential grid around the pool? Did you both bond the pool motors and add supplemental grounding electrodes, or did you use the grounding electrodes in place of equipment grounding/bonding conductors?

I know the above questions sound quite critical, but I am really more interested in learning; what are good criteria for adding more grounding electrodes then explicitly mentioned in code?

Thanks,
Jon
 
  #12  
Old 04-26-06, 08:52 PM
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My apologies

My apologies, I came to this forum thinking that I could help. Instead, I feel as though I stepped in to a ring of competition
of " who's the best " and " who knows more" I have no need to impress. I'll just leave the competition and do something more productive. Excuse me for trying to help.
 
  #13  
Old 04-26-06, 08:54 PM
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If grounding rod indeed carries current to the earth, isn't more the better? If a house consumes a large amount of current, and if a portion of the current is going to flow through neutral to grounding rods, aren't more grounding rods better? At least, it's not going to hurt. Right? What about lightning surge? Lower grounding rod resistance will better take care of lightning surges. Am I correct? Also, grounding rods will rust and resistance is going to go up. So why not drive in a lot to begin with?

NOT an electrician either by training or education
 
  #14  
Old 04-26-06, 09:17 PM
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> If a house consumes a large amount of current,
> and if a portion of the current is going to flow through neutral
> to grounding rods, aren't more grounding rods better?

No. Zero are necessary for normal operation.


> At least, it's not going to hurt. Right?
Actually, that's a tough call. On a livestock/chicken farm, ideally the MBJ goes (in the first means of disconnection) on the pole right under the meter 15' from the pole with the transformer on it.

This reduces stray voltage substantially. In such a case, more ground rods don't hurt anything.


> What about lightning surge?
> Lower grounding rod resistance will better take care of lightning surges.
> Am I correct?

Yes. But this pertains more to if you have air terminals.
Think of it this way: Lightning just arced 4 miles through air to get to your wires.
Do you really think it makes much difference whether the resistance of your ground rod is 5 ohm or 50 ohm?
The lightning is going wherever it goes.


> Also, grounding rods will rust and resistance is going to go up.
Use copper clad rods. Rusted rods aren't just higher resistance, they are practically non-conductive.


> So why not drive in a lot to begin with?
Because they don't do much.
 

Last edited by bolide; 04-27-06 at 02:21 AM.
  #15  
Old 04-26-06, 09:47 PM
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jamead65, sorry you feel this way. I just asked a question, that's all. If you feel threatened by this that's a shame.

There is a reason why the NEC only requires two rods maximum. Bolide had the answer. "Because they don't do much."

Adding more ground rods without even testing the resistance is like throwing money at a problem without even knowing there is a problem. It's like giving a well person antibiotics.

The pool is an issue that I also question. What does a pool have to do with groud rods? What are they connected to? NO where in Art.680 do they even mention grounding electrodes. If you have rods associated with a pool are they bonded to the service GES?
 
  #16  
Old 04-26-06, 09:57 PM
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Not threatened in the least

Again with the questions. Ok, you win, you know a lot. Is there anything saying I can't use that many?
 
  #17  
Old 04-26-06, 10:05 PM
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Now you're just being adolescent. It's not that I know a lot. I simply question any real electrician who installs ground rods for a pool, or someone who install eight for any reason (other than for a lightning rod system). To me this is a biggie in the "Knowing what your doing" department.

You can install as many as you heart desires. There is no maximum. How you install and bond them only concerns me.
Have fun.
 
  #18  
Old 04-27-06, 04:57 AM
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Why? Are you the inspector? Is it your house that I referring to? I don't see why you be so concern? If you'd like, I'll give you the address and you can look at it yourself since you are so concern.
 
  #19  
Old 04-27-06, 05:07 AM
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The above ground portion of my house grounding rod is steel. My house is about 20 years old, and it must be corroded in the soil by now. Do you recommend I drive in a copper clad steel rod and move the bonding to the new one?
Thanks.
 
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Old 04-27-06, 05:18 AM
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Please stop the irrelevant personal attacks and posts or I will close the thread.
 
  #21  
Old 04-27-06, 05:41 AM
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puter,

The NEC permits copper ground rods, or somewhat thicker ferrous ground rods.

I would suggest that you can _probably_ simply leave well enough alone, however if you are going to the effort of replacing your ground rod(s) I would recommend that you use solid copper rods, and that you replace the ground rod clamp with one that you are sure is listed for the application.

-Jon
 
  #22  
Old 04-27-06, 05:43 AM
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Originally Posted by jamead65
From the meter pan I used two 200amp 44space panels .
I have a big house coming up, and I could use all the spaces I can get. Where can I find some of these panels? What brand were they?
 
  #23  
Old 04-27-06, 05:52 AM
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jmead65,

This is an internet forum. No one checks credentials at the door. We all try to help with what knowledge we have, and we all have to recognize that our knowledge is limited. I learn new things every day in my discussions here.

When someone suggests doing some aspect of an installation that is well in excess of what code requires, without providing logical justification for why they are doing this, then it suggests to me that perhaps they have not thought out all of the implications of what they are doing. At the same time is makes me curious: what do I not know on this topic.

Suggesting 'more is better' can be quite misleading in a DIY forum; if you don't also remind your readers of the implications of the more is better approach. For example, if someone suggests that 10ga wire is 'better' then 14ga wire for 15A branch circuits, then they'd best add reminders about box and conduit fill requirements!

That is why I asked my questions.

-Jon
 
  #24  
Old 04-27-06, 09:28 AM
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Originally Posted by puter
The above ground portion of my house grounding rod is steel.
But it is clamped below ground?

> My house is about 20 years old, and it must be corroded in the soil by now.

Probably so.

> Do you recommend I drive in a copper-clad steel rod and move the
> bonding to the new one?
Or bond them both.
I am sufficiently convinced that a copper-on-rust connection is very high impedance.
If your electrical equipment/connection is corroded (steel or aluminum), you need to correct it.
 
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