# Installing a ground plate



## rrolleston (Oct 17, 2011)

Would have to look but think ground plates have to be 2'x2'.

(7) Plate Electrodes. Each plate electrode shall expose not
less than 0.186 m2 (2 ft2) of surface to exterior soil. Elec-
trodes of bare or conductively coated iron or steel plates
shall be at least 6.4 mm (1⁄4 in.) in thickness. Solid, uncoated
electrodes of nonferrous metal shall be at least 1.5 mm (0.06
in.) in thickness.


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## joecaption (Nov 30, 2011)

How are you trying to drive it in?


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## a_lost_shadow (Dec 18, 2011)

Um, 2'x2' = 4 square feet (or 8 if you're counting both sides).


To the OP, I wouldn't trust a nut/bolt/ring connection to keep tight as it corrodes over the years. Doing a quick search shows that many commercially sold grounding plates have the wire welded to the plate.

How did you try to drive the ground rod in? I'm assuming that you tried both the water method and the hammer method. I've heard tales of folks using a fence post driver to get a ground rod in quickly. Also did you make sure that the tip of your ground rod didn't mushroom on your first few attempts, causing the later attempts to be more difficult?


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## benjamincall (Apr 25, 2008)

rrolleston said:


> Would have to look but think ground plates have to be 2'x2'.
> 
> (7) Plate Electrodes. Each plate electrode shall expose not
> less than 0.186 m2 (2 ft2) of surface to exterior soil. Elec-
> ...


Does that mean a 1'x1' plate would suffice?




joecaption said:


> How are you trying to drive it in?


I've been driving the rods using a post driver and a 16 lb. sledge. I can usually push them in by hand until they hit a rock.


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## itsnotrequired (Apr 30, 2010)

1'x1' would be acceptable, provided the thickness matched the metal type. also note that it must be minimum 30" below grade.

horizontal rod works as well provided vertical and 45 degree driving were attempted and failed. any buried horizontal rod will need to be 30" deep and need to be minimum 8' long.


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## a_lost_shadow (Dec 18, 2011)

A question out of curiosity, do you have a reference for the 30"? Looking at the 2011 NEC, I just see "below the permanent moisture level", which I take as call the AHJ and find out. Also, at least one grounding plate's installation instructions called for 36".


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## itsnotrequired (Apr 30, 2010)

a_lost_shadow said:


> A question out of curiosity, do you have a reference for the 30"? Looking at the 2011 NEC, I just see "below the permanent moisture level", which I take as call the AHJ and find out. Also, at least one grounding plate's installation instructions called for 36".


250.53(H) Plate Electrode

'Plate electrodes shall be installed not less than 750 mm (30 in.) below the surface of the earth.'

where is the 'below the permanent moisture level' statement found?


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## rrolleston (Oct 17, 2011)

benjamincall said:


> Does that mean a 1'x1' plate would suffice?


2' square plate is how I understand it and min 1/4" thick.


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## k_buz (Mar 22, 2012)

rrolleston said:


> 2' square plate is how I understand it and min 1/4" thick.


From the quoted code reference it says that 2 square feet have to be in contact with earth. A 1'x1' has 2 square feet surface area if you consider both sides of the plate. 

I had to give that one a second thought as well.


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## itsnotrequired (Apr 30, 2010)

rrolleston said:


> 2' square plate is how I understand it and min 1/4" thick.


2 square feet need to be in contact with the earth. unless one side of the plate is coated, a 1' x 1' plate will suffice since both sides of the plate are in contact with the earth.


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## rrolleston (Oct 17, 2011)

Just read it again sounds like that would be work if they count the top and bottom surface of the plate.


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## itsnotrequired (Apr 30, 2010)

think of it this way: a 3/4", 8' rod has about 226 sq in of metal surface exposed to the soil. a 1'x1' plate has 288 sq in of exposed metal (not counting the 'height' of the plate), very close to the area of a rod.


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## a_lost_shadow (Dec 18, 2011)

itsnotrequired,
Thanks, I saw the "below permanent moisture" level in 250.53(A)(1) and skimmed right over both (G) & (H). Doh. Either I'm going blind, or I need new glasses. :whistling2:


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## itsnotrequired (Apr 30, 2010)

a_lost_shadow said:


> itsnotrequired,
> Thanks, I saw the "below permanent moisture" level in 250.53(A) and skimmed right over both (G) & (H). Doh. Either I'm going blind, or I need new glasses. :whistling2:


me too, i found it in (A) after my post. classic nec to have similar requirements in multiple spots.


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## joed (Mar 13, 2005)

I don't think you can just buy a chunk of steel and use it for a ground plate. You need to buy an actual ground plate. They have a rod welded on for connection with a proper ground clamp same as used for ground rods.


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## rrolleston (Oct 17, 2011)

I was searching and I see they make them in copper too.


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## k_buz (Mar 22, 2012)

What do those cost?


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## joed (Mar 13, 2005)

k_buz said:


> What do those cost?


In Canada about $30.


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## benjamincall (Apr 25, 2008)

a_lost_shadow said:


> To the OP, I wouldn't trust a nut/bolt/ring connection to keep tight as it corrodes over the years. Doing a quick search shows that many commercially sold grounding plates have the wire welded to the plate.
> 
> How did you try to drive the ground rod in? I'm assuming that you tried both the water method and the hammer method. I've heard tales of folks using a fence post driver to get a ground rod in quickly. Also did you make sure that the tip of your ground rod didn't mushroom on your first few attempts, causing the later attempts to be more difficult?


I called the two supply houses in our area, and neither one knew what a ground plate is. If I shouldn't assemble my own ground plate, I guess I'll just have to bite the bullet and dig that 8' trench to bury the rod horizontally. 

On a side note, I'm considering installing one of these when I build a house: http://www.lyncole.com/index.php?p_resource=items_item&p_itm_pk=3


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## Code05 (May 24, 2009)

Where in the NEC does it say that a ground plate must be listed or commercially made?

Is a ground pipe electrode listed?


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## benjamincall (Apr 25, 2008)

I haven't seen any proscription. One of the other forum contributors suggested my design idea might not maintain a good bond between the plate and the GEC. Do you have an opinion on my initial post or a design idea of your own to share?

Edit: I drove one ground rod down about five feet and had to cut it off because I couldn't pull it out of the rock with a floor jack. Should I tie that partial rod to the other electrodes? How about tapping the well casing, too?


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## itsnotrequired (Apr 30, 2010)

Code05 said:


> Where in the NEC does it say that a ground plate must be listed or commercially made?
> 
> Is a ground pipe electrode listed?


it doesn't say it needs to be listed, as near as i can tell. listings help the ahj avoid having to make judgements and determine acceptability.


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## rrolleston (Oct 17, 2011)

How deep would an 8' rod be at a 45 deg angle?


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## benjamincall (Apr 25, 2008)

rrolleston said:


> How deep would an 8' rod be at a 45 deg angle?


About 5'8". Prety hard to achieve with our rocky soil.


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## Code05 (May 24, 2009)

benjamincall said:


> I haven't seen any proscription. One of the other forum contributors suggested my design idea might not maintain a good bond between the plate and the GEC. Do you have an opinion on my initial post or a design idea of your own to share?


I merely cite code, there is no prohibition about designing your own plate other then it must be approved.

110.2 Approval. The conductors and equipment required or
permitted by this Code shall be acceptable only if approved.


Approved. Acceptable to the authority having jurisdiction.


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## itsnotrequired (Apr 30, 2010)

Code05 said:


> I merely cite code, there is no prohibition about designing your own plate other then it must be approved.
> 
> 110.2 Approval. The conductors and equipment required or
> permitted by this Code shall be acceptable only if approved.
> ...


and that's where listings help. AHJ just has to see the listing and knows it is 'pre-approved'. takes guesswork out of the equation.

i mean, a homeowner could make their own homemade NM-B cable that meets all the technical requirements of the listed NM-B cable but i know if i was the inspector, i sure as heck wouldn't want to try to determine if it was acceptable or not. listed NM-B cable? inspector glances at it and moves on.


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## benjamincall (Apr 25, 2008)

Code05 said:


> I merely cite code, there is no prohibition about designing your own plate other then it must be approved.
> 
> 110.2 Approval. The conductors and equipment required or
> permitted by this Code shall be acceptable only if approved.
> ...


How would you build a plate electrode if you were going to do it? Apparently, I won't be able to buy the plate locally.


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## itsnotrequired (Apr 30, 2010)

benjamincall said:


> How would you build a plate electrode if you were going to do it? Apparently, I won't be able to buy the plate locally.


to be minimum code-compliant, you would need to follow 250.52(A)(7). this means:



2 sq ft minimum in contact with the soil (1'x1' plate is fine since top and bottom touch the soil)
bare or conductively coated iron or steel, minimum 1/4" thick
or solid, uncoated nonferrous metal 1.5 mm thick
this is the absolute bare minimum and no guarantee the AHJ would accept.


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## benjamincall (Apr 25, 2008)

itsnotrequired said:


> to be minimum code-compliant, you would need to follow 250.52(A)(7). this means:
> 
> 
> 
> ...


I'm just unclear on the best method to connect the GEC to the plate. I describe how I would do it in the first post.


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## Code05 (May 24, 2009)

itsnotrequired said:


> and that's where listings help. AHJ just has to see the listing and knows it is 'pre-approved'. takes guesswork out of the equation.
> 
> i mean, a homeowner could make their own homemade NM-B cable that meets all the technical requirements of the listed NM-B cable but i know if i was the inspector, i sure as heck wouldn't want to try to determine if it was acceptable or not. listed NM-B cable? inspector glances at it and moves on.


NM must be listed

334.6 Listed. Type NM, Type NMC, and Type NMS cables
shall be listed.

Ground plates - no.


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## Code05 (May 24, 2009)

benjamincall said:


> How would you build a plate electrode if you were going to do it? Apparently, I won't be able to buy the plate locally.


I would bury the rods myself.


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## itsnotrequired (Apr 30, 2010)

Code05 said:


> NM must be listed
> 
> 334.6 Listed. Type NM, Type NMC, and Type NMS cables
> shall be listed.
> ...


bah, picked a bad example.


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## joed (Mar 13, 2005)

If I was to make one I make it like the picture. Take your flat plat and weld a rod to so you can use a proper ground clamp to connect the ground wire. Take a piece of one of those cut off ground rods and weld it flat to the top surface of the plate, leaving 4-6 inches sticking out so you can fasten the cable.


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