[TowerTalk] [Bulk] Re: [Bulk] Antenna to Shack Ground Connection

[Grant Saviers]

Thanks Jim, Mike and David for the data.  6 ga has plenty of strength 
and soils here are pretty benign, so I will go with it.

Grant KZ1W


On 2/2/2015 7:54 PM, Jim Lux wrote:
> On 2/2/15 9:30 AM, Grant Saviers wrote:
>> I'm considering what gage wire to use for grounding tower, ground rods
>> and Ufer guy anchors together, and need about 500' so cost is an issue.
>> The best pricing for solid bare copper I have found is $1.80/ft 2ga;
>> $0.85/ft 4ga; and $0.42/ft 6ga.
>>
>> I suspect the code requirement for 2ga on 200/400a entry panels is to
>> handle the maximum interruption current of the affiliated main breaker.
>> The fusing currents for 2/4/6 awg copper are 72Ka/36Ka/28Ka respectively
>> which makes some sense.  (although with the usual 2 to 4 ohm rod to
>> ground connection, how can current ever get beyond a few hundred amps?
>> Not so if the ground is domestic water supply iron or copper.)
>>
>> However, in the case of a lightning strike is fusing current important
>> since currents are likely an order of magnitude larger or more? My
>> historical examination of HV tower grounds often found big wire 2/0, 4/0
>> etc. so is that needed for a strike and it really doesn't matter much
>> between 2/4/6 ga, they fuse?  Or is the strike current so short that
>> fusing isn't a concern?  Then 6 ga would be ok to tie stuff together.
>>
>> Is there some engineering basis for 2ga for ground rod and tower to
>> shack wiring?
>>
>
>
> Lightning is high peak, but low "action" (the averaged power 
> dissipation, in units of amps^2*seconds) because it's a short pulse 
> (50 microseconds)
>
> Upshot is AWG 10 will handle a pretty large lightning discharge. (and 
> lots of lightning rod grounds around the world are in that sort of 
> size range.. a few mm in diameter)
>
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