[RE-wrenches] Incompatible Metals

Fri Jan 14 14:51:28 PST 2011

300.3(A) prohibits the use of XHHW outside of a recognized wiring method, which means you need a conduit or raceway. You can use USE-2 in an exposed outdoor location only because 690.31(B) allows it, but only for module interconnections.

Scott

On Jan 14, 2011, at 11:45 AM, Kelly Keilwitz, Whidbey Sun & Wind wrote:

> 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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