Module grounding revisited [RE-wrenches]

[Nick Nicholas]

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.

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----- 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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