[RE-wrenches] Incompatible Metals

Fri Jan 14 15:06:09 PST 2011

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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>>
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