# Installing 2 ground rods



## caliwest (Apr 29, 2009)

I have to install 2ground rods for a new panel. My question is, how? Do i daisy chain the grounds, or can i put 3 ground clamps on one rod, thus having one ground going to the panel, the 2nd going to the other ground rod, and the third going to the cold water?


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## brian john (Mar 11, 2007)

Unless there are local rules daisy chain, 3 seperate conductors, 1 to the cold water 1 to the rods and daisy chain them, run to the water pipe then the rods or run to the rods then the water pipe.


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## Mac Hine (Apr 28, 2009)

You can also do something like this. This is a Mike Holt graphic. It, by no means , is not the only way to do it but it will give you an idea or two.


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## caliwest (Apr 29, 2009)

so if im reading your post right, I cannot, or i should not put those 3 clamps on 1 rod, thus branching off that one rod to the panel, cold water pipe, and the other rod. Or i think what your telling me is i should just have one conducter from the panel to the first rod, then jumper a conducter from the first rod to the second rod, then jumper from the 2nd rod to the cold water pipe...


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## Jeff000 (Jun 18, 2008)

I would have 2 on each, one rod to the panel, one to the water, and then tie them together. 

I have no idea what the clamp is called, but it is made for two connections to the ground rod. I would use that over 2 olive clamps.


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## caliwest (Apr 29, 2009)

Gotcha


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## BuzzKill (Oct 27, 2008)

To save cash, you can run #6 from your panel to to within 5' of the cold water entrance to the property and then from your meter or disco, run #6 to the first ground rod and then daisy chain to the next one, at least 6' feet away.


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## 480sparky (Sep 20, 2007)

The first rod only needs one acorn (connector). Just run the wire through and on to the next rod.


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## BuzzKill (Oct 27, 2008)

Yes! Acorns and granny clamps, I still get them confused.


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## waco (Dec 10, 2007)

I agree with 480sparky, run the GEC to the first rod, through an acorn to the second rod to an acorn. I have had inspectors require two GECs when two panels were involved and I think the GEC must be unbroken to both rods unless you are prepared to use a crimp splice. I never splice the GEC simply because some inspectors just won't have it.

I wonder why you have to have two ground rods when you have a water pipe. Usually, the water pipe is the primary ground and the rod is the secondary.


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## 480sparky (Sep 20, 2007)

waco said:


> ........I wonder why you have to have two ground rods when you have a water pipe. Usually, the water pipe is the primary ground and the rod is the secondary.


It's the 25-ohm rule. If you can't get 25 ohms or less with one rod, you drive a second. It doesn't matter if the two rods have 25 ohms or not.

250.56.

How do you get a rod with less than 25 ohms? How do you even know what the resistance is? Well, you could pony up and buy a $4-digit meter that will tell you, but I can drive a lot of ground rods for that same thousand bucks.


Here's some reading from the 30s or 40s:


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## Mac Hine (Apr 28, 2009)

480sparky said:


> Well, you could pony up and buy a $4-digit meter that will tell you, but I can drive a lot of ground rods for that same thousand bucks.


 
Or you could put in a ufer (CEE) and never drive a ground rod at all and still save that $1,000.


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## Jeff000 (Jun 18, 2008)

Mac Hine said:


> Or you could put in a ufer (CEE) and never drive a ground rod at all and still save that $1,000.


what is a ufer?


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## Magnettica (Jan 23, 2007)

Jeff000 said:


> what is a ufer?


Ufer is the guy who invented the concrete-encased electrode.


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## 480sparky (Sep 20, 2007)

Jeff000 said:


> what is a ufer?


*Google* is our friend.

Ufer ground.


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## TheRick (Apr 13, 2008)

480sparky said:


> The first rod only needs one acorn (connector). Just run the wire through and on to the next rod.


That is how I always do it.....our POCO requires 2 no matter what you show for a resistance reading, and they have to be 8' apart, not the 6' required by the NEC.


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## 480sparky (Sep 20, 2007)

TheRick said:


> ........., and they have to be 8' apart, not the 6' required by the NEC.


And a real easy way to measure that is to drive one rod, then use the second eight-footer to space it from the first.


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## TheRick (Apr 13, 2008)

480sparky said:


> And a real easy way to measure that is to drive one rod, then use the second eight-footer to space it from the first.


 
EXACTLY :thumbsup:


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## brian john (Mar 11, 2007)

480sparky said:


> And a real easy way to measure that is to drive one rod, then use the second eight-footer to space it from the first.


And once again if you want them to be effective (which is the point of installing them I think) drive them 16 feet or more apart.


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## waco (Dec 10, 2007)

Good discussion. In my location, the earth is damp and a good conductor. I know it is a code thing, but I still question the technical argument in the code regarding the effectiveness of ground rods and their practical use. I think lightning protection became confused with the need to establish a nearly zero potential between the "building" and the power ground neutral.

I have always thought every new construction foundation footer should have a length of rebar left accessible for grounding, along with the remesh in the slab, but I guess the code doesn't agree.

But, what the heck, right?


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## TheRick (Apr 13, 2008)

brian john said:


> And once again if you want them to be effective (which is the point of installing them I think) drive them 16 feet or more apart.


That all depends on your definition of effective, how low of a ground resistance are you looking for, or are you simply trying to make it a safe, code compliant install.

I will not argue the fact that further apart is better, but if you already have an effective ground with the first rod, and are simply installing the second to make the inspector happy what is the point of going further than required?


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## Zog (Apr 15, 2009)

TheRick said:


> what is the point of going further than required?


To be outside the sphere of infulence of the other rod.


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## TheRick (Apr 13, 2008)

Zog said:


> To be outside the sphere of infulence of the other rod.


I understand why you would want to move out of the sphere of influence if your goal is to lessen the resistance to ground.......but what if the first rod is plenty low, and you are just adding the second to be code compliant?


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## Zog (Apr 15, 2009)

TheRick said:


> I understand why you would want to move out of the sphere of influence if your goal is to lessen the resistance to ground.......but what if the first rod is plenty low, and you are just adding the second to be code compliant?


You dont know the 1st is low without testing it. and 99% of EC's dont have the equipment or training to properly test. If one is <25 ohms in most areas you dont need a 2nd rod.


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## TheRick (Apr 13, 2008)

Zog said:


> You dont know the 1st is low without testing it. and 99% of EC's dont have the equipment or training to properly test. If one is <25 ohms in most areas you dont need a 2nd rod.


In my area the POCO requires 2 at least 8' apart regardless of how low a resistance reading is. 

My question is........why is it so many here believe a ground rod resistance tester is such an amazing tool that only a select few can own, let alone know how to operate. They are readily available, and if you can use a clamp on ammeter, you can use one!


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## Zog (Apr 15, 2009)

TheRick said:


> In my area the POCO requires 2 at least 8' apart regardless of how low a resistance reading is.


Then testing is a moot point. 



TheRick said:


> My question is........why is it so many here believe a ground rod resistance tester is such an amazing tool that only a select few can own, let alone know how to operate. They are readily available, and if you can use a clamp on ammeter, you can use one!


You cant test a single ground rod with a clamp on tester. That is one of the many limitations of a clamp on group tester. There are only certian applications where they can be used and even then thier accuracy is questionable. They are misused more often than propery used and are not an acceptable means of groud testing by ANSI or NETA, not to mention most other testing specs for commisioning projects. 

Most specs require a 3 or 4 point fall of potential test with at least 3 test points at 52%, 62%, and 72% of the distance to Z. Many times 10 or more points are required and plotted to prove the reading is accurate by showing a plauteu region.


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## waco (Dec 10, 2007)

Well, as an old metrologist (calibration technician), I'd be hard pressed to come up with a repeatable,reliable method of measuring ground rod resistance (or conductivity), so I can sort of see why some jurisdictions just want something.

I routinely measure voltage between the GEC and the panel neutral before I hook up the GEC, which is an effective method measuring the "circuit" from PGN to the local earth ground and I can honestly say, I have never seen a panel ground bar have voltage on it once the GEC is hooked up.

Of course, like all science, I might be seeing what I want to see, but I doubt very much two ground rods are any improvement over one.


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## calimurray (Apr 29, 2007)

we hardly ever put two ground rods in anymore, we did for awhile but now he just uses one 3/4" 10 foot ground rod and most times it passes inspection, it also I think has allot to do with the ground and how its sediments are!

In some places we are required to use two rods, and the ground wire has to be continuous through both rods, ground lugs, grounding bushings with no breaks in the wire.


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## Zog (Apr 15, 2009)

waco said:


> Of course, like all science, I might be seeing what I want to see, but I doubt very much two ground rods are any improvement over one.


Lots of testing has been done on this:

Total resistance with 2nd rod driven is 50-65% of single rod, depending on spacing 

Total resistance with 3nd rod driven is 35%-50% of single rod, depending on spacing


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## Zog (Apr 15, 2009)

calimurray said:


> we hardly ever put two ground rods in anymore, we did for awhile but now he just uses one 3/4" 10 foot ground rod and most times it passes inspection, it also I think has allot to do with the ground and how its sediments are!


Driving 2 rods is much more effective (See above post). A 10ft rod only reduces the resistance by about 5% or so, anything longer than 8 ft dosent do much at all. A 3/4" rod only decreases resistance by 5-10% depending on what test data you look at, either way, not much.


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## brian john (Mar 11, 2007)

Jobs where we are involved in with ground rods typically we are driving anywhere from 10-300 rods. My feeling on a second rod for services and the proper spacing has to do with anything I do in my profession. If it is worth doing at all it is worth doing right and in this case BEING A PROFESSIONAL I want to try and achieve the lowest resistance with what is required.

On a 400 Amp service you could seat the conductor termination connector (lug) 1/2 on the bus and it would work just fine, but why would you? The correct way is to seat the connector fully on the bus ensuring a low resistance, professional installation, I see the 2nd rod as the same issue.


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## waco (Dec 10, 2007)

My argument is that there is no solid science for the net effectiveness of multiple ground rods because there's really no solid science defining the matter of "earth ground" relative to power ground neutral (PGN). I suspect anything that pretty much eliminates any EMF between local "earth ground" and PGN at that location is adequate for both equipment, people, and animals.

I mean, if the conductivity between two ground rods eight feet apart is better than the conductivity between a water pipe or a well casing fifty feet from the ground rod, so what?

Point is, no EMF between the local earth ground and the local PGN.

This on top of my looking at another fire-trap house that should have been torn down fifty years ago. Family lives there that can no more afford an electrician than it can afford another half gallon of milk and I'm supposed to just walk away?

Man....


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