[RE-wrenches] Incompatible Metals

Fri Jan 14 23:43:35 PST 2011

Hi Kelly:
    Are you sure about the XHHW listing.  Doesn't that designate aluminum wire?  
You mentioned CU before.  

    I have seen some discolloration from copper wire against module frames, but 
not real corrosion.  

 Nick Soleil
Project Manager
Advanced Alternative Energy Solutions, LLC
PO Box 657
Petaluma, CA 94953
Cell:   707-321-2937
Office: 707-789-9537
Fax:    707-769-9037

________________________________
From: "Kelly Keilwitz, Whidbey Sun & Wind" <kelly at whidbeysunwind.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Fri, January 14, 2011 3:06:09 PM
Subject: Re: [RE-wrenches] Incompatible Metals

Scott,
300.3(2) allows grounding and bonding conductors to be outside of a raceway. See 
250.134(B), exception 2. 

Kelly Keilwitz, P.E. 
Principal
Whidbey Sun & Wind
Renewable Energy Systems
NABCEP Certified PV Installer
WA Electrical Administrator
987 Wanamaker Rd.
Coupeville, WA 98239
kelly at whidbeysunwind.com
PH & FAX: 360.678.7131

On Jan 14, 2011, at 2:51 PM, Scott McCalmont wrote:

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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