Module grounding revisited [RE-wrenches]

[Tom Lane, Energy Conservation Services]

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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