ground rod question [RE-wrenches]

[Joel Davidson]

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In 1984, I suggested to a PV DYIer living in lightning country 30 north of 
New Orleans to run #6 wire the 200' between the ground rod at his array and 
the ground rod at his charge controller and battery bank. Lightning fried 
his charge controller and blew the top off one of his golf cart batteries. 
He replaced the destroyed equipment, added the rod-to-rod wire and never had 
another lightning problem. Since then I tell (not suggest) installers that 
they must tie all ground rods together.
Joel Davidson

----- Original Message ----- 
From: "David Palumbo, Independent Power & Light" <ipl at sover.net>
To: <RE-wrenches at topica.com>
Sent: Sunday, May 21, 2006 10:46 AM
Subject: RE: ground rod question [RE-wrenches]


>
> Darryl,
>
> Here's a hypothetical for you.
>
> Off grid system with ground mounted top of pole array located 150'(or 
> more)
> from the house.
> Do you still run a ground wire back to tie in with the other ground rods?
>
> I have always done it like you state, with two ground rods connected to a 
> #6
> bare ground wire (in the trench with the conduit for the transmission 
> wires
> (high voltage to MX60)) which is connected to the system ground rods.
>
> Now with copper becoming so dear I certainly do not want to waste it is 
> not
> necessary. What say you wrenchers?
>
> David
>
>
> Hello Peter
> Below is my understanding of the codes regrading
> grounding.  I have certainly been wrong in the past
> and have had many discussions with inspectors on
> grounding.
> As I see it the ground rod on a PV array is for two
> purposes, One to divert any lightening induced surges
> to earth protecting your equipment and Two to protect
> grounded people from any errant voltages/currents that
> they might contact during fault conditons.  (part two
> is what the electrical inspector is looking for)
>
> For part one The shorter the ground lead the better.
> and this is not NEC but NFPA 780  78? the lightening
> protection code.  The connection should have only
> radius  bends, and a larger outside diameter and of
> course a good ground connection.  Y0our array will act
> as a capacitor with the sky and as lightening
> discharges occur within the county the sky earth
> changes potential and your array will have differing
> amounts of energy to dissipate.  I always drive two
> ground rods and separate them by there sphere of
> influence 8 to 10 feet.
>
> In case two the grounding is to protect against any
> "generated fault currents" currents from the PV system
> or back feed through the system from the Utility or
> other source that should happen to get on the frame.
> This is the one that the inspector is concerned with.
> You have a separately derived system and it needs a
> grounding electrode system.  You can either bring the
> ground wire back to the service location and ground
> the array with one rod or ground with two rods at the
> array.  I ALWAYS GROUND AT THE ARRAY AND BERING BACK A
> GROUNDING WIRE.  When wiring a garage for example the
> ground rod is always placed
>
> Hope this helps and is correct.
> Darryl
>
> --- Peter Duchon <info at asappower.com> wrote:
>
>>
>> What is the max. distance an 8' ground rod can be
>> from a ground mounted
>> array?   Or where is considered best placement for
>> ground rods on
>> ground-mounted arrays?   Ok, that's plural, two
>> questions.  Pertinent NEC
>> 2005 section would be great if anybody has that info
>> handy otherwise.
>>
>> Thanks,
>> Peter
>> asappower.com
>>
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