[TowerTalk] [Bulk] Re: copper or galvanized ground rods in red SC clay

[Grant Saviers]

CADweld is the brand name of the copper thermite mixture for welding 
wire to rods.  Commercial electrical supply houses stock it (Platt 
here).  There are many configurations of wire size, rod diameter and 
wire orientation so look at the Erico catalog to find the right models.  
The "one time use" ceramic molded are the cheapest for the small number 
of rods normally in a tower install.

I was skeptical of the upsizing of ground wires to rods in the latest 
codes, i.e. #6 > #2.  After installing some more rods and measuring  
them with a ground resistance meter I think the larger diameter wire is 
essentially a horizontal rod with rods spaced 2x their length.  I've 
also measured the resistances 3 times - very dry soil, saturated soil, 
and frozen soil, the total ground rod resistance was 7.9, 5.3 and 6.6 
ohms respectively, all below the recommended 10 ohms or less in the 
code.  Besides the obvious that wet earth is more conductive it seems 
frozen earth is less conductive (makes sense as ice is less conductive 
than water).  So "next time" I would bury the top of the rods and the #2 
wire below the frost line (only about 1 foot here).  The  "average" rod 
is about 60 ohms as is the Ufer in the 4x6' concrete floor of the shack 
at the base of the tower.  60 ohms seems in the ballpark for rods in 
average ground.

I bought a Duoyi DY1000A Ground Resistance Tester, cost about half of 
what I could rent one for and 1/10 of what Greenlee wants. It seems to 
be very repeatable and comes with a cal loop.  For $10 more this model 
does more
http://www.ebay.com/itm/DUOYI-Leakage-Current-And-Grounding-Resistance-Clamp-on-Earth-Tester-DY1200-/321969345083?hash=item4af6de523b:g:I3MAAOxy69JTDW~A

One thing in laying out rods is to have the wires in a radial (star) 
connection to the tower, no loops or cross connections.  Then each rod 
or string of rods can be measured (actually it is a little more 
complicated than that, it's explained in the manual).

Grant KZ1W


On 1/9/2016 10:52 AM, StellarCAT wrote:
> good point... maybe make the spacing from the tower closer to 6 or 
> even 8'. I don't know if you can overkill it as long as you take into 
> account the possibility of current saturation in the soil - for the 
> cost of 3 ground rods and some #3 or #4 wire I'd rather chance the 
> overkill then not.
>
> I just did a Google search and it appears the thicker coatings on the 
> copper (10 mils is standard) outlasts the 3.9mil coating on galvanized 
> ~40 years to 10-15. So seems copper is the way to go (also they're 
> higher tensile strength - ~58K vs > 90K for the copper).
>
> Gary
>
> -----Original Message----- From: Kelly Taylor
> Sent: Saturday, January 9, 2016 1:47 PM
> To: StellarCAT
> Cc: tower
> Subject: Re: [TowerTalk] copper or galvanized ground rods in red SC clay
>
> Here's an interesting question: if the concrete base is an effective 
> ground connection, do you get more value by placing the rods a rod 
> length away from the base?
>
> If the idea of separation is to prevent saturation during a strike, 
> isn't the base and rod combo at risk of saturation if the rods are too 
> close to the base?
>
> 73, Kelly
> ve4xt
>
> Sent from my iPhone
>
>> On Jan 9, 2016, at 12:41 PM, StellarCAT <rxdesign at ssvecnet.com> wrote:
>>
>> Just curious if anyone has experience using either of these over a 
>> number of years – whether they’re ‘eaten away’ one any faster than 
>> the other.
>>
>> Also the conductivity issue – not sure if it matters all that much 
>> for lightning protection. Don’t know if you can ‘weld’ copper wire to 
>> the galvanized ones using the welding devices (can’t remember what 
>> they’re called at the moment).
>>
>> Finally: with 3 on a tower – one on each leg – the rule is to 
>> separate them by their length correct? So if I have 3 each on about 
>> 5’ of wire from the tower that would mean each would be over 8’ 
>> (8.66’)  from each other .... this is correct – spaced at least equal 
>> to their length (depth)?
>>
>> Gary
>> K9RX
>>
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