[RE-wrenches] Incompatible Metals

Fri Jan 14 11:45:18 PST 2011

Peter,
Yes the #10 XHHW (2) we use is green-jacketed, and 90˚ rated. We get  
it through our local electrical supply house.

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

On Jan 14, 2011, at 11:04 AM, Peter Parrish wrote:

> 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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