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
[email protected]
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
[email protected]
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
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