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Author Topic: Multiple Ground Rods  (Read 3417 times)
KG0DB
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Posts: 52




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« on: April 01, 2012, 02:46:21 PM »

What is the correct way to connect multiple ground rods at the base of a vertical antenna?  Are they daisy chained or all connected to one another?  What gauge/kind of wire is recommended and what kind of connectors are recommended for a standard ground rod?  The old fashion "acorn" type connectors are okay for solid strand wire up to about 10 gauge, maybe 8 gauge.  I don't see that as much protection.  Is there any sort of pattern recommended in locating the ground rods? 
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W6RMK
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Posts: 651




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« Reply #1 on: April 01, 2012, 02:54:02 PM »

Electrical code requires AWG 6 (or bigger) for bonding. Exothermic welding or listed compression clamps to do the connection.

That said, hard solder (brazing) probably meets the intent of the code (you gotta use a torch, after all) and is a practical approach. Clamps are a pain, because they could loosen, so you can't bury the connection.

daisy chain or parallel depends more on the physical arrangement of them.  If they're in a line, then daisy chain (i.e. there's not much point in running parallel wires). If they're around a central point, then parallel (star) is better. 

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KG0DB
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« Reply #2 on: April 01, 2012, 03:21:25 PM »

Gas welding #6 to the ground rod is no problem.  How is it connected to the stainless steel radial plate?  Same, gas welding?
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K3VAT
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Posts: 715




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« Reply #3 on: April 01, 2012, 05:36:21 PM »

What is the correct way to connect multiple ground rods at the base of a vertical antenna?  Are they daisy chained or all connected to one another?  What gauge/kind of wire is recommended and what kind of connectors are recommended for a standard ground rod?  The old fashion "acorn" type connectors are okay for solid strand wire up to about 10 gauge, maybe 8 gauge.  I don't see that as much protection.  Is there any sort of pattern recommended in locating the ground rods? 
 

Hi Don,  A 'must read' set of documents on this subject are on this website: http://www.protectiongroup.com/Grounding/FAQ and most tech literature is available here:
http://www.protectiongroup.com/Utility/Knowledge-Base

73, Rich, K3VAT
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KG0DB
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Posts: 52




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« Reply #4 on: April 01, 2012, 07:45:09 PM »

Thank you.  The articles appear to be promising for information.
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K9KJM
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Posts: 2415




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« Reply #5 on: April 01, 2012, 09:04:55 PM »

I agree.   Torch welding with high silver/copper/nickel content braze rods works well and is lower cost than Cadwelding, But more time consuming. (Silfoss, Silvalloy, etc  "hard" silver solder rods)

Ground rods should be spaced about twice the distance apart as the depth, In normal soil.

Number 6 (Or heavier) copper wire is good advice.

Tips on doing it all on a lower budget:
http://www.scribd.com/anon-849269/d/14868226-lightning-protectiontaming-thors-thunderon-a-budget

(Give that site plenty of time to load)
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N3ZC
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Posts: 1281




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« Reply #6 on: April 02, 2012, 04:24:46 AM »

Connected mine (16 ground rods) together with #4 solid copper wire and used Cadweld Plus One Shots to weld the wire to the ground rod at each junction... http://www.erico.com/products/plusoneshot.asp

  Good Luck!
                73'..Tom N3ZC
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K0ZN
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Posts: 1548




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« Reply #7 on: April 03, 2012, 09:39:13 PM »


Question:  I have seen a number of ground rod clamps, UL rated and marked "for direct burial". These are apparently bronze with bronze bolts/fasteners.
It would seem that a couple of these, while not as good as welding, *should* stay tight with a large cable. 

Utility companies use similar clamps on lines and grounds

Does anybody have info or accurate first hand knowledge about the failure rate/mode on these types of  ground rod clamps ??

73,  K0ZN

 
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W9IQ
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Posts: 102




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« Reply #8 on: April 03, 2012, 10:21:39 PM »

Hi Jon,

I have used these type of clamps in the past and have not had any problems. I did however, put a 4 inch PVC pipe around the top of the ground rods cut flush with the ground. I capped this with a flat 4 inch PVC pipe cap. This gave me about 12 inches of exposed ground rod below the ground level that I could inspect simply by prying off the PVC cap.

Over time, some soil and grass accumulates over the cap so it is almost invisible to the casual eye. It really works nicely because the clamp assembly is easily inspected and as long there isn't standing water in the area, it also keeps the clamp assembly dry minimizing corrosive effects.

For the earlier question about what wire to use to bond the ground rods together, remember that the issue during a lightning strike is the surface area of the conductor, not the gauge per se. This is why you often see flatter bar stock used because for the same amount of copper, there is more surface area to handle the skin effect of the lightning pulse. Copper pipe is also a reasonable alternative. The challenge of course, is properly bonding the bar stock to the ground rods which is why most opt for heavy gauge wire. If you can weld the grounding system, then consider a solution that maximizes the surface area of the conductors.

- Glenn DJ0IQ and W0IQ
« Last Edit: April 03, 2012, 10:23:18 PM by W9IQ » Logged
W9IQ
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Posts: 102




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« Reply #9 on: April 03, 2012, 10:45:29 PM »

I neglected to mention in my earlier post that a proper copper joint compound should be used on the clamps to minimize corrosive effects.

- Glenn DJ0IQ and W9IQ
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N3ZC
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Posts: 1281




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« Reply #10 on: April 04, 2012, 07:05:37 AM »

Why not just CadWeld them for a good thermal-weld joint instead of just clamping them together?

Here's one of mine:  https://picasaweb.google.com/goodenbed/TowerAndA3SInstall#5407472996866728626

Beat's clamping them..but if you clamp, shine up the copper where you are joining them, and use a joint compound like this: http://www.gacopper.com/ConnectionGrease.html

I.C.E. used to sell it, but they've changed.

Good Luck!

     73'..Tom N3ZC
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K0ZN
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Posts: 1548




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« Reply #11 on: April 04, 2012, 07:37:39 PM »


 Thanks for the comments/help/input; much appreciated. 

I have several ground rods with AWG # 2 attached with these types of rod clamps.  I guess I will dig up a couple of them
(top of the rods are about 6" below the surface) and see how secure/tight the cable is, check for corrosion, etc.  Some of them have been down 8 years, so it should be a realistic finding.  Fortunately, our soil does not seem corrosive.... at least it appears that way so far.

 73,  K0ZN
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