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<DIV>Peter:</DIV>
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<DIV>In my experience and understanding of the relative electro-negativity or
electrode potential of these two metals, there is not an issue for the copper to
erode to the point of ground failure - the aluminum goes first. In a
marine environment, especially salt water areas, all metals
eventually dissolve, much more quickly when there is galvanic action due to
dissimilar metals. Copper is considered more "noble" than aluminum (this is
an archaic chemical reference) and will erode the aluminum, eventually
causing a break in the surface interaction, and the galvanic action slows
or stops.. </DIV>
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<DIV><FONT lang=0 size=3 face=Arial FAMILY="SANSSERIF" PTSIZE="12"><I>Patrick A.
Redgate<BR>Ameco Solar, Inc.<BR>7623 Somerset Blvd,<BR>Paramount, CA 90723<BR><A href="http://www.solarexpert.com/">www.solarexpert.com</A><BR><A href="http://www.amecosolar.com/">www.amecosolar.com</A><BR>562-633-4400</I></FONT></DIV></DIV>
<DIV> </DIV>
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<DIV>In a message dated 1/14/2011 10:14:16 A.M. Pacific Standard Time,
kelly@whidbeysunwind.com writes:</DIV>
<BLOCKQUOTE style="BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px"><FONT style="BACKGROUND-COLOR: transparent" color=#000000 size=2 face=Arial>Peter,<BR>I have never understood the common practice of using bare
copper <BR>ground wire on and against aluminum frames and modules. It
always has <BR>been a dissimilar metals issue. Just look anywhere copper
has set <BR>against aluminum for awhile.<BR>We use #10 green jacketed Cu
USE or XHHW conductor and strip away the <BR>jacket at each lug, using
No-Ox on that section of bare wire at the <BR>lug. The wire can be
tucked in to the module frames and with the PV
<BR>conductors.<BR><BR>Kelly Keilwitz, P.E.<BR>Whidbey Sun &
Wind<BR>Renewable Energy
Systems<BR>kelly@whidbeysunwind.com<BR>360-678-7131<BR><BR><BR><BR><BR>On Jan
14, 2011, at 7:36 AM, Peter Parrish wrote:<BR><BR>> One of my students who
is currently responsible for standing for <BR>> inspection<BR>> at
their company encountered a inspector who made an interesting <BR>>
point about<BR>> incompatible metals (i.e. copper and anodized
aluminum).<BR>><BR>> The PV system in question used outdoor rated lay-in
lugs to bond the <BR>> rails<BR>> to bare copper wire (so far so
good). The ground wire was then zip- <BR>> tied to<BR>> the rail to
carry it to the point where it entered a junction box <BR>> along
with<BR>> the rest of the PV conductors.<BR>><BR>> The inspector was
concerned with the fact that the bare copper was in<BR>> contact with the
aluminum rails and that this might cause galvanic <BR>>
corrosion<BR>> and subsequent failure of the grounding.<BR>><BR>> I
have never encountered this issue before and I wonder if anyone <BR>>
else has<BR>> and what was the outcome.<BR>><BR>> As an aside: I do
know that 10 AWG and 12 AWG solid bare copper <BR>> wire can
be<BR>> purchased "pre-tinned" (maybe not tin per se, but coated). We did
so <BR>> by<BR>> mistake. We used it up, but not before one
inspector questioned its <BR>> use for<BR>> the purpose of
grounding our system. We showed him the UL label on <BR>> the
spool<BR>> and scraped off the coating to expose the copper core and
that <BR>> satisfied<BR>> him. To this day I don't know if the use
of this wire for grounding <BR>> was<BR>> among its intended
purposes.<BR>><BR>> - Peter<BR>><BR>> Peter T. Parrish, Ph.D.,
President<BR>> California Solar Engineering, Inc.<BR>> 820 Cynthia Ave.,
Los Angeles, CA 90065<BR>> CA Lic. 854779, NABCEP Cert. 031806-26<BR>>
peter.parrish@calsolareng.com<BR>> Ph 323-258-8883, Mobile 323-839-6108,
Fax 323-258-8885<BR>><BR>><BR>>
_______________________________________________<BR>>
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