Peter: 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.. Patrick A. Redgate Ameco Solar, Inc. 7623 Somerset Blvd, Paramount, CA 90723 _www.solarexpert.com_ (http://www.solarexpert.com/) _www.amecosolar.com_ (http://www.amecosolar.com/) 562-633-4400
In a message dated 1/14/2011 10:14:16 A.M. Pacific Standard Time, ke...@whidbeysunwind.com writes: 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 ke...@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.parr...@calsolareng.com > Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 > > > _______________________________________________ >
_______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
