Module grounding revisited [RE-wrenches]

Brad Bassett bsbassett at earthlink.net
Wed Oct 30 19:25:35 PST 2002


I agree that the ground wire in most arrays should not be considered to 
be exposed to physical damage, so #10 should be adequate for most 
arrays. Any disageement there?

I find that on the Schott/Sharp modules that in order to get ANY 
conductance to the module frame I must seriously scratch through the 
coating on the Aluminum. I believe that this is just a thick anodizing, 
but can't confirm that there isn't some other coating as well.

We have seen many module grounds with serious corrosion problems, 
especially in hot humid climates, not so much in dry climates. I have 
not seen how well the standard Siemens connection holds up. The ASE-300 
modules have a stainless nut riveted into the frame at the factory, and 
so long as in humid conditions you use something between the copper wire 
and the aluminum frame it works well. There aren't so many modules to 
ground either with such large modules.

I have seen a star washer used between the module frame and rack and 
then the rack grounded (with all of the same caveats as module frame 
grounding) work well, but as pointed out by John Wiles, is not approved 
by NEC. Now if a module manufacturer gets UL listing on the whole panel, 
rack and modules, then whatever grounding method they use and supply 
will be OK. This is what Solarex did for their self racking Millenia 
modules, where there was a "grounding clip" with a star washer between 
modules and a single lug for the whole row of moudules.

BTW - The green grounding screws are probably NOT approved for outdoor 
use. Neither are most standard aluminum lugs. Of course the hardware 
supplied with a UL listed module IS approved for the use. This may be a 
detail that most inspectors will not see, so long as they see some sort 
of grounding, but...

Brad Bassett


William Miller wrote:
> Brad and others:
> 
>  
> On ground wire sizing, the 2002 code says this:
> 
> 	250.120 Equipment Grounding Conductor Installation.
> 	An equipment grounding conductor shall be installed 
> 	in accordance with 250.120(A), (B), and (C).
> 
> 	(C) Equipment Grounding Conductors Smaller Than 6 AWG.
> 	Equipment grounding conductors smaller than 6 AWG shall be protected 
> from physical damage by a raceway or cable armor except where run in 
> hollow spaces of walls or partitions, where not subject to physical 
> damage, or where protected from physical damage.
> 
> One might contend that the grounding wire is protected from physical 
> damage or not subject to physical damage hidden behind a module that 
> will break if subject to physical damage and particularly if the modules 
> are on a roof, or better yet, flat on a roof.
> 


Brad Bassett
Schott Applied Power 
Tumwater, WA office
bsbassett at earthlink.net

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