[TowerTalk] [Bulk] Antenna to Shack Ground Connection

[Grant Saviers]

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?

73,
Grant KZ1W


On 2/2/2015 3:17 AM, Jim Thomson wrote:
> Date: Sun, 1 Feb 2015 20:44:30 -0500
> From: Hans Hammarquist via TowerTalk <towertalk at contesting.com>
> To: towertalk at contesting.com
> Subject: [TowerTalk]   Antenna to Shack Ground Connection
>
> ##  The braid wont  handle the current......so u still require 2 ga bare, stranded copper wire between base of tower and shacks  spg.   The 2 ga stranded, bare wire is buried in the dirt aprx 1-3 feet.
> Then its in direct contact with the dirt.   Even if the braid of  coax used, the coax would still have to be bonded to both top and bottom of the tower.   It still wouldn’t work, since the braid is covered
> with insulation..and not in contact with the soil.  Around here, the electrical inspector  will go crazy if you don’t  install the bare, stranded, min 2 ga  copper wire between base of tower and shacks spg.
>
> Jim  VE7RF
>
>
>
>
> Brian,
>
>
> Yes, you are right all the shield of the feed-lines are connected (or should be connected) tween the tower and the shack ground. The risk of getting the shields fused (burned off) is reduced with a separate grounding wire between the tower and the shack. Large enough your shack might even survive a direct hit.
>
>
> Again, the ground wire should be run close to the feed lines in order to minimize induced current from near strikes.
>
>
> Hans - N2JFS
>
>
>
> -----Original Message-----
> From: Brian Carling <bcarling at cfl.rr.com>
> To: Bill Turner <dezrat at outlook.com>
> Cc: Towertalk <towertalk at contesting.com>
> Sent: Fri, Jan 30, 2015 11:10 pm
> Subject: Re: [TowerTalk] Fwd:  Antenna to Shack Ground Connection
>
>
> Most of us have that already in the form of out coax feedline's outer conductor.
> Typically this is grounded at the antenna and also in the shack. Am I right?
>
> Best regards - Brian Carling
> AF4K Crystals Co.
> 117 Sterling Pine St.
> Sanford, FL 32773
>
> Tel: +USA 321-262-5471
>
>
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