Module grounding revisited [RE-wrenches]

[matthew tritt]

Nick,

Most probably, the modules you tested have a very good, thick layer of
aluminum oxide (anodizing). The panels which I've tested, that have
excellent conductance, probably have lousy, porous anodization. But, if the
aluminum with the great anodizing is such a good insulator against
conductance, why does it need grounding at all???????????????

Matt
----- Original Message -----
From: "Nick Nicholas" <APS at SBCGLOBAL.NET>
To: <RE-wrenches at topica.com>
Sent: Wednesday, October 30, 2002 9:33 AM
Subject: Re: Module grounding revisited [RE-wrenches]


> Hi Tom Lane:
>     You had mentioned that anodizing aluminum frames should not effect
> grounding.  I have found that continuity can not be found between two
points
> on a solar module without scratching through the coating on the frame.  It
> is the anodized coating that causes this resistance to continuity.
>
> www.alternativepowersystems.com
> aps at sbcglobal.net
> 135 Colfax Ave.
> Grass Valley, CA 95945
> (530) 274-0588 phone
> (530) 274-0589 fax
> ----- Original Message -----
> From: "Tom Lane, Energy Conservation Services" <tom at ecs-solar.com>
> To: <RE-wrenches at topica.com>
> Sent: Wednesday, October 30, 2002 3:49 AM
> Subject: Re: Module grounding revisited [RE-wrenches]
>
>
> > There is no way anodizing can effect grounding in point of fact
anodizing
> > is similar to sanding the aluminum as finish . Mill finish anodizing or
> > brite aluminum finish should make abetter finish than raw aluminum
Gator
> > TOM ----- Original Message -----
> > From: "matthew tritt" <solarone at charter.net>
> > To: <RE-wrenches at topica.com>
> > Sent: Tuesday, October 29, 2002 11:32 PM
> > Subject: Re: Module grounding revisited [RE-wrenches]
> >
> >
> > Brad,
> >
> > I have measured the resistance many times between module frames and rack
> > members, and (virtually) always found 0 to .01. to be the reading. Are
you
> > (and the NEC under the impression that anodizing creates a barrier to
> > conductance? I'd say proving that would be an interesting project.
Proving
> > that copper sandwiched between two pieces of aluminum will create
> corrosion
> > would be a much easier job!
> >
> > Matt
> > ----- Original Message -----
> > From: "Brad Bassett" <bsbassett at earthlink.net>
> > To: <RE-wrenches at topica.com>
> > Sent: Tuesday, October 29, 2002 7:43 PM
> > Subject: RE: Module grounding revisited [RE-wrenches]
> >
> >
> > > The trick is get electrical contact between the module frame and the
> > > rack. Many modules frames are so well anodized that electrical contact
> > > can't be counted on by just bolting them together. There must be a way
> > > to break through the anodized coating to get contact.
> > >
> > > One method used by some is to put a star washer (stainless of course)
> > > between the module frame and rack where it is bolted down. Whether
this
> > > gives adequate conductance or not I'm not sure. I also wonder how it
> > > will do over a period of years. It also wouldn't work with a clamp
down
> > > type rack.
> > >
> > > Another corollary issue is how to get a good, long lasting ground on
any
> > > aluminum rack or module. Somewhere there is likely to be a problem
with
> > > corrosion between the aluminum frame and the copper grounding wire.
> > > Inserting something stainless between might slow it down some. The
best
> > > I've seen is a copper lug (GBL-4DB from Ilsco) held with a stainless
> > > bolt with a stainless washer between it and the aluminum frame (with
> > > copper ground wire of course).
> > >
> > > I have a question about the size of the ground wire. I think I've read
> > > in the NEC that AWG #6 stranded or #8 solid is required where subject
to
> > > physical damage. Does ground wiring in an array qualify as subject to
> > > physical damage (if the combiner is adjacent)? Or is #10 ground wire
> > > adequate? Since #10 or smaller interconnect wire seems to be accepted,
> > > maybe that's all that's needed for ground wire. Any thoughts?
> > >
> > > Thanks
> > > Brad Bassett
> > >
> > > William Miller wrote:
> > > One concept I had been wanting to research is that of grounding
> > > > only the rack frame.  The Code seems to allow this:
> > > >
> > > > (A) Equipment Secured to Grounded Metal Supports. Electrical
equipment
> > > > secured to and in electrical contact with a metal rack or structure
> > > > provided
> > > > for its support and grounded by one of the means indicated in
250.134.
> > > >
> > >
> > >
> > > Brad Bassett
> > > bsbassett at earthlink.net
> > >
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