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Author Topic: Copper for ground rods  (Read 3686 times)
K6RQR
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Posts: 436




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« Reply #15 on: April 23, 2017, 08:02:55 AM »

To K6AER -
 I'm not trying to measure ground conductivity with an ohmmeter. I was just checking to see that the potential conductivity of the ground rod in the soil was maximized by the surface of the rod being polished. The ohmmeter apparently confirmed that the oxidation on its surface was an impediment to that.

Bruce  K6RQR
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AA4HA
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Posts: 2626




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« Reply #16 on: April 23, 2017, 08:30:47 AM »

Usually when setting an array of ground rods the proper spacing is the sum of the lengths of both rods; If you have two, eight foot rods, the spacing should be sixteen feet.

The idea being that the rods should be separate enough that they are outside of the zones of influence of each other to maximize the conduction area to the earth. It is more than just how many square inches are in contact with dirt, it is the entire area around the rod that is forming part of the ground system.

Depth is important to reach a point where the soil moisture levels are consistent; Typically the first foot or so of earth is subject to the seasons, freeze-thaw and rain-drought. But you can also end up falling for the "mo is betta" trap of trying to put in a 100 foot ground system, thinking that it is ten times better than a single, ten foot ground rod. An overly long single ground rod actually has an inductive effect that will delay the discharge current and increase the probability of damage.

I would not wax ground rods; you are taking something that you want to be a good conductor and covering it with a substance that is an electrical insulator? You can make a ground rod nice and shiny but it is going to oxide back up in a matter of hours after you drive it (just the way that chemistry works). All you will have accomplished is to reduce the thickness of the copper plating on the ground rod.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KE6EE
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Posts: 2568




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« Reply #17 on: April 23, 2017, 10:09:33 AM »

I would not wax ground rods.

Nor would I. I forgot to add the smiley to my recommendation.  Grin
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KL7CW
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Posts: 514




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« Reply #18 on: April 23, 2017, 10:20:57 AM »

HMS,
     I do not know why your rental place did not have a 120 volt reasonable size domo (jack hammer).  I live in a very small town and the rental place (I think part of a national chain) had at least two of them.  They knew all about ground drive bits and rented me one for $10.  Originally a BIG guy rolled out a monster machine...I said NO.  They then brought out a somewhat smaller machine which I could at least lift.  I think it had some sort of strange plug on the end, but they included a free adaptor for a regular 120 volt extension cord.  My normal size extension cord worked fine with my standard 20 amp breakers.  Before this I called a few other places and they also had similar machines and knew all about ground rod bits which they rented.
     It was not too hard to get an 8 ft ground rod started....just climbed up a bit on a ladder and pounded it in a little, then used a fence post driver to pound in a few more feet.  At this time I could lift the jackhammer over my head either from the ground...some rods, or from a platform about two feet high.  I could not reach the on-off switch on some of them so had my wife just plug it in and soon I could reach the switch myself.  The hammer was heavy for me, but I am 76 years old and not especially strong, but it should be easy for younger husky folks. With two people it should be very easy.
     I am not saying this method is best...just saying it worked fine for me in our rather rocky soil.  I do not remember how heavy my machine was, but am sure it was at least 40 pounds....it felt very heavy.
                 Rick   KL7CW
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AA4PB
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Posts: 14922




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« Reply #19 on: April 23, 2017, 11:02:11 AM »

I purchased a 40lb jack hammer on closeout from Harbor Freight for $130 several years ago. It works fine to drive an 8-foot ground rod. I have someone on the ground steady the ground rod while I get on a step ladder with the jack hammer to get it started. In this soil, it only takes a few minutes to put in an 8-foot ground rod.
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Bob  AA4PB
Garrisonville, VA
K6RQR
Member

Posts: 436




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« Reply #20 on: April 23, 2017, 11:39:08 AM »

AA4HA -
 Is it really true that the rods will oxidize back up in a matter of hours after they are driven into the ground? That doesn't seem right to me. Have you experienced this? I'm not saying that they wouldn't develop a layer of oxidation eventually but it seems unlikely to me that it would happen so fast.

73,
Bruve  K6RQR
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W8JX
Member

Posts: 13268




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« Reply #21 on: April 23, 2017, 12:12:37 PM »

Usually when setting an array of ground rods the proper spacing is the sum of the lengths of both rods; If you have two, eight foot rods, the spacing should be sixteen feet.

The idea being that the rods should be separate enough that they are outside of the zones of influence of each other to maximize the conduction area to the earth. It is more than just how many square inches are in contact with dirt, it is the entire area around the rod that is forming part of the ground system.

Funny thing is the power company drive one rod straight in fans 3 or 4 more ground rods out  driven at abt a 45 to 60 degree angle from ground level from a central entry point and then ties them together here installing grounds for power pole transformers by houses
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
KM1H
Member

Posts: 4722




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« Reply #22 on: April 23, 2017, 12:23:37 PM »

Suggestion: Go to home depot and rent the largest hammer drill they have. Make sure the chuck is big enough to fit over the ground rod. At $35 for 4 hours it is worth it.

You can bury a 8' rod in a minute or two. Here in NH its rocky and there is a thin layer of Granite every few feet. I start up a step ladder and almost cant get down it fast enough.

When it is this easy it is easy to put several longs rods in. Just make sure there isnt a septic, gas pipe or buried electrical in the rod's path....

Not in my part of NH where solid ledge is common except in the lowest areas and swamps!!  I hired a dynamite blaster in order to situate the foundation. And the well digger hit ledge at 2' and had to go 600' for water; the joys of living on top of a hill but it is a killer for DX and VHF and above Grin   Some on this hill went to 1500' and came up dry which is why the homes are few and far between.

Almost horizontal is the only way that works for the ground rods here. Guy anchors for the towers were drilled in 8' using a mobile compressor and a 2" diameter drill bit. Then 8' utility company grade rock anchors installed, locked in place, and then epoxy poured in.

Carl
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