How good is a ground plate?

[George Stolz]

I'm curious, does anyone have experience with ground plates?

Say a code minimum ground plate grounding electrode, how would it compare to a ground rod?

This is actually a relevant discussion I'm having, not just idle curiousity. I appreciate any insight you can offer!

 

[quogueelectric]

I'm curious, does anyone have experience with ground plates?

Say a code minimum ground plate grounding electrode, how would it compare to a ground rod?

This is actually a relevant discussion I'm having, not just idle curiousity. I appreciate any insight you can offer!

I have never used one yet i live on a glacial sand and rock deposit. I feel that plastic explosives would help you sink a ground rod and would be much more fun!!

 

[ceknight]

Say a code minimum ground plate grounding electrode, how would it compare to a ground rod?

They both look about the same, installed.

 

[Pierre C Belarge]

Seeing as I do not have much faith in the performance of standard ground rods in general applications, how much better or worse can a plate actually be?

I would say that the soil structure is a determining factor as well, depth of plate, etc...

 

[ultramegabob]

I have never used one, but my guess is it boils down to how much surface area your plate or rod has and what the soil conditions are where you are using them, given the conditons are the same for either install, I would think they would perform the same.

 

[ItsHot]

harder to drive?

harder to drive?

I would think that ground plates would be harder to drive!:grin:

 

[George Stolz]

There is a pretty funny story to this involving an inspector and a Ufer cut by a framer, but I'm not sure how much I'd want to share publicly. I made a point of mentioning the forum in the discussion.

I was doing my part, asking if I could get a ground rod as an alternative "this time." He suggested a ground plate, and it struck me as odd.

I don't have a dog in the fight. The homeowner would wind up mining for the Ufer, but the conversation left me curious if anyone here had actually ever installed a ground plate, and if it was any better than a rod.

Perhaps I will share the rest of this story tonight, but for now, I think I better leave it untold.

 

[dereckbc]

Generator stations use them a lot, but they are buried very deep directly under the generator pad. I have never heard of them being used anywhere else.

 

[zog]

I'm curious, does anyone have experience with ground plates?

Say a code minimum ground plate grounding electrode, how would it compare to a ground rod?

This is actually a relevant discussion I'm having, not just idle curiousity. I appreciate any insight you can offer!

One of the major factors of grounding effectiveness is total surface area making contact between the rod or plate and the soil. Thats why increasing the length and/or diameter of a rod can lower resistance so I would imagine a plate would be much more effective. However, I have never tested one so I can't provide any hard data.

(Brian John, any experience here?, now Wiggum has me curious)

 

[Pierre C Belarge]

One of the major factors of grounding effectiveness is total surface area making contact between the rod or plate and the soil. Thats why increasing the length and/or diameter of a rod can lower resistance so I would imagine a plate would be much more effective. However, I have never tested one so I can't provide any hard data.

(Brian John, any experience here?, now Wiggum has me curious)

Increasing the diameter of a rod has a much smaller percentage of the effectiveness of the rod as compared to increasing the length of the rod.

 

[jghrist]

The IEEE Green Book, IEEE Recommendations for Grounding of Industrial and Commercial Power Systems, Std 142 has equations for both rods and plates.

One rod: R = [rho/(2?pi?L)]?[ln(4?L/a) - 1]
rho = resistivity in ohm-cm
L = rod length in cm
a = rod radius in cm
R = resistance in ohms

Horizontal round plate: R = rho/(8?a) + [rho/(4?pi?s)]?[1 - (7?a^2)/(12?s^2) + (33?a^4)/(40?s^4)]

a = plate radius in cm
s/2 = depth in cm

 

[zog]

Increasing the diameter of a rod has a much smaller percentage of the effectiveness of the rod as compared to increasing the length of the rod.

Yep, I never said otherwise.

 

[ultramegabob]

Increasing the diameter of a rod has a much smaller percentage of the effectiveness of the rod as compared to increasing the length of the rod.

I had a funny comment for that statement, but I think I better not.... :grin:

 

[LarryFine]

I had a funny comment for that statement, but I think I better not.... :grin:

Lemme guess: "That's what she said."

 

[guitarsarge]

We've been required to install these since we adopted 2005, now we're on 2008.
I don't know if it is more effective, but it sure takes a lot more labor. Also, the need for a return trip to back fill the hole.

We're required to dig a 30"x30"x30" hole.

250.53(H) Plate Electrode. A plate electrode is required on all electric service upgrades or change-outs as part of the grounding system. The grounding plate electrode shall be installed not less than 750mm (30 in.) below the surface of the earth. The plate electrode shall comply with 250.52 (A)(6) (Plate Electrodes).

 

[brian john]

We've been required to install these since we adopted 2005, now we're on 2008.
I don't know if it is more effective, but it sure takes a lot more labor. Also, the need for a return trip to back fill the hole.

We're required to dig a 30"x30"x30" hole.

250.53(H) Plate Electrode. A plate electrode is required on all electric service upgrades or change-outs as part of the grounding system. The grounding plate electrode shall be installed not less than 750mm (30 in.) below the surface of the earth. The plate electrode shall comply with 250.52 (A)(6) (Plate Electrodes).

Let me guess the Head Inspector graduated from The Merlin Institute? The HooDoo VooDoo black magic school of electricity. Being it is in back fill for a certain amount of time it is LESS effective would be my guess. What is the frost depth in your area.

 

[ibew501ed]

Generator stations use them a lot, but they are buried very deep directly under the generator pad. I have never heard of them being used anywhere else.

I believe if you are installing wood poles that require grounding some utilities will do the grounding before installing the pole by wrapping the base of the pole with a copper (.06") sheet material wide enough to give you 2 sq.ft. on 1 side since the other side is not in contact with earth. Then connect a GEC to the copper and strap it up the pole so when the pole is dropped in the hole your done

 

[guitarsarge]

Let me guess the Head Inspector graduated from The Merlin Institute? The HooDoo VooDoo black magic school of electricity. Being it is in back fill for a certain amount of time it is LESS effective would be my guess. What is the frost depth in your area.

Lol! Central Texas = frost depth is about 3 inches... :grin: We run into caliche and rock straight away. It's fun!

I would thinks with the back fill being loose for awhile after the back fill would cause it to be less effective until it settles completely. Now, I'm curious... I should collect some data and see what others think here?

 

[JohnJ0906]

I seem to recall reading on this forum about a study conducted on the effectiveness of the various grounding electrodes, and plates came in dead last.

It would have been several years ago.