[RE-wrenches] Incompatible Metals

[Peter Parrish]

Great idea Kelly! I didn't know one could get green jacketed USE or XHHW. Do
you have a source? Also, do you think that we might need wire rated "-2" for
90 deg C wet locations. I know that this is not a current carrying
conductor, but roof tops are definitely 90 deg C wet environments. Your
thoughts?

- Peter

                                                     
 Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com  
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885

 
-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kelly
Keilwitz, Whidbey Sun & Wind
Sent: Friday, January 14, 2011 10:14 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Incompatible Metals

Peter,
I have never understood the common practice of using bare copper  
ground wire on and against aluminum frames and modules. It always has  
been a dissimilar metals issue. Just look anywhere copper has set  
against aluminum for awhile.
We use #10 green jacketed Cu USE or XHHW conductor and strip away the  
jacket at each lug, using No-Ox on that section of bare wire at the  
lug. The wire can be tucked in to the module frames and with the PV  
conductors.

Kelly Keilwitz, P.E.
Whidbey Sun & Wind
Renewable Energy Systems
kelly at whidbeysunwind.com
360-678-7131




On Jan 14, 2011, at 7:36 AM, Peter Parrish wrote:

> One of my students who is currently responsible for standing for  
> inspection
> at their company encountered a inspector who made an interesting  
> point about
> incompatible metals (i.e. copper and anodized aluminum).
>
> The PV system in question used outdoor rated lay-in lugs to bond the  
> rails
> to bare copper wire (so far so good). The ground wire was then zip- 
> tied to
> the rail to carry it to the point where it entered a junction box  
> along with
> the rest of the PV conductors.
>
> The inspector was concerned with the fact that the bare copper was in
> contact with the aluminum rails and that this might cause galvanic  
> corrosion
> and subsequent failure of the grounding.
>
> I have never encountered this issue before and I wonder if anyone  
> else has
> and what was the outcome.
>
> As an aside: I do know that 10 AWG and 12 AWG  solid bare copper  
> wire can be
> purchased "pre-tinned" (maybe not tin per se, but coated). We did so  
> by
> mistake. We used it up, but not before one inspector questioned its  
> use for
> the purpose of grounding our system. We showed him the UL label on  
> the spool
> and scraped off the coating to expose the copper core and that  
> satisfied
> him. To this day I don't know if the use of this wire for grounding  
> was
> among its intended purposes.
>
> - Peter
>
> Peter T. Parrish, Ph.D., President
> California Solar Engineering, Inc.
> 820 Cynthia Ave., Los Angeles, CA 90065
> CA Lic. 854779, NABCEP Cert. 031806-26
> peter.parrish at calsolareng.com
> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
>
>
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