[RE-wrenches] Galvanic compatibility of commonly usedsolar materials

[Wind-sun.com]

Something we found out over 20 years ago is that you have to be extremely 
careful about how you ground DC systems, especially if there is any other 
metal of any type in the vicinity in or on the ground. We have seen it 
destroy underground pipes and even metal fence posts.

You can get stray currents from things you never even imagined, and that 
current is what causes a lot of the galvanic corrosion.  In one case a 
previous installer had used an underground tank for a positive ground 
system, and after about 5 years it was almost totally destroyed - just lucky 
the tank was not used for anything but water.

To be doubly safe, best to light up the system and actually put a digital 
amp meter in series with the ground wire(s). Clamp on ammeters may not work, 
as sometime the current is only a few to a few hundred ma. Sometimes you can 
get stray currents to objects you thought were isolated.

..................................................................................................
Northern Arizona Wind & Sun - Electricity From The Sun
Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
..................................................................................................
----- Original Message ----- 
From: " Jeff Yago" <jryago at netscape.com>
To: <daryl_solar at yahoo.com>; "RE-wrenches" 
<re-wrenches at lists.re-wrenches.org>
Sent: Sunday, February 01, 2009 10:16 PM
Subject: Re: [RE-wrenches] Galvanic compatibility of commonly usedsolar 
materials


>I recently inspected a large ground mount off-grid system about 3 years old 
>that was installed by others. I would have used a #6 bare copper ground 
>wire due to being exposed almost 100 feet of array length and connected to 
>several ground rods with no conduit, but the installer had used #10 which 
>still barely met code, but sure was flimsy. Anyway, this small ground wire 
>was sagging down in many places along the array length due to about a 
>quarter of the galvanized steel self-tapping screws holding the copper 
>against the aluminum had totally dissolved.
>
> We always use the cadmium plated copper grounding blocks and stainless 
> steel screws to attach the #6 copper ground wire, and I can see now just 
> how fast the galvanic action can dissolve metal when you don't use 
> stainless steel hardware.
>
> Jeff Yago
>
> _____________________________________________________________
> Netscape.  Just the Net You Need.
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: 
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>