[RE-wrenches] Incompatible Metals

[Peter Parrish]

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