[RE-wrenches] Incompatible Metals

Sat Jan 15 11:18:44 PST 2011

Hi Nick,
On the jacket from a roll in the shop: it's Cu, Type XHHW-2,  
"XLPE" (whatever that means). Also type RW90.
-Kelly

Kelly Keilwitz, P.E.
Whidbey Sun & Wind
Renewable Energy Systems
kelly at whidbeysunwind.com
360-678-7131

On Jan 14, 2011, at 11:43 PM, Nick Soleil wrote:

> 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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