[RE-wrenches] bare tinned solid copper

[R Ray Walters]

Is this in a high corrosive area near the ocean? Even so, I've seen bare copper do just fine. i think the focus should be on the connectors to the modules and structure. I've seen the lay in lugs deteriorate rapidly, while the copper just develops a green patina. Consider using the WEEB grounding system for the modules through the frame, tie to each rod at each array, and tie it all your grounding together through the EGC. 
If the goal is lightning protection, you don't want to create a lightning loop by double connecting the ground rods. You could oversize the EGC to reduce the potential between the grounding electrodes, but making a 2nd connection between the electrodes is like running a wire from your house's ground electrode to your neighbors. It's already bonded through the grid neutral, you don't make a 2nd connection. Unfortunately a couple of illustrations in the NEC handbook shows double connections like this, but:
A) its not required by code (all grounds should be bonded through the EGC to satisfy 250.50)
B) Its not done in other types of wring (grid in your neighborhood)
C) It violates one of the cardinal rules of lightning protection experts (read Lightning Protection & Grounding Solutions for Comm Sites by Polyphaser)
D) Even my clamp on ground impedance tester is not designed for the double connections, and won't work correctly.

R. Walters
ray at solarray.com
Solar Engineer




On May 6, 2010, at 7:43 AM, Phil Schneider wrote:

> Engineer wants to see #6 above grade (fine), but #2 direct buried between ground rods (seems excessive).
> 
> Phil Schneider
> Creative Energies
> 
> 
> 
> On Wed, May 5, 2010 at 10:44 PM, August Goers <august at luminalt.com> wrote:
> Phil,
>  
> The inspector wants to see #2 tinned copper for equipment ground in exposed areas? Or is he referring to the grounding electrode conductor? This kind of stuff gets mixed up all the time in my neck of the woods...
>  
> -August
>  
>  
>  
> August Goers
>  
>  
> Luminalt Energy Corporation
> O: 415.564.7652
> M: 415.559.1525
> F: 650.244.9167
> www.luminalt.com
>  
> From: re-wrenches-bounces at lists.re-wrenches.org [re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Phil Schneider [phil at creativeenergies.biz]
> 
> Sent: Wednesday, May 05, 2010 8:24 AM
> To: RE-wrenches
> Subject: [RE-wrenches] bare tinned solid copper
> 
> Wrenches,
> 
> We are working through submittal steps for a 75 kW ground mounted array.  The array is split into 8 subarrays.  There is a combiner or junction box at each subarray, with a ground rod spec'd at each subarray, underneath the "box station", with a bare stranded #6 from an equipment grounding bus to the rod, and equipment grounding conductors through conduit between a ground bus in each box.  15A fuses in combiners, and 100A fuses at inverter.
> 
> The engineer we're working with to stamp the plans wants to see bare, tinned, solid copper anywhere this equipment ground is in the elements, and wants to see #2 (!) bare, tinned, solid copper cadwelded and direct-buried between all 8 rods and back to the existing AC grounding electrode system.  He says this is the standard (from telecom, I'm afraid) to ensure that all the rods are at the same potential.  No Code reference, and I don't see anything in article 250 along these lines.  Hard to convince him that #6, untinned, across the board is adequate.
> 
> In the end, we'll probably go ahead and do it because it is relatively low cost and we want a good relationship here, but I'm wondering if anybody else out there is using bare tinned copper in this type of application, and I'd like more info on this to make a better argument next time.
> 
> Phil
> 
> Phil Schneider
> Creative Energies
> 
> 
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