690.47 (was Enphase) [RE-wrenches]

Fri Jun 13 12:04:55 PDT 2008

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Mark,

I agree that here is ambiguity in this section.  In the quote below, 
it is unclear as to me as to what is located within 6 ft of the 
premise wiring electrode.

Quote:
"Exception No. 2:  Additional array grounding electrode(s) shall not 
be required if located within 6 ft of the premises wiring electrode."

I had interpreted this to mean that if the rooftop array was within 6 
feet of the premise wiring electrode, the additional electrode would 
not be required.  If the additional electrode was within 6 feet of 
the premises wiring electrode, and therefore not be required, then it 
is there but not required.  It would only not be required if it were 
there, and within 6 feet.   So it must mean within 6 feet of the 
array.  If that is the case, does this mean within 6 feet 
horizontally, since most roofs are over 6 feet high?

On the issue of the other GEC, I also don't see how we get past the 
requirements of 250.166 (a) , which is referenced in 
690.47(c)(7).  Inspectors we have dealt with seem ok using wires down 
to the neutral conductor size.

Drake

At 10:07 AM 6/13/2008, you wrote:

>Ray,
>
>As far as 2008 690.47(D), as usual the code is not clear.
>
>"Grounding electrode shall be installed.....as close as practicable..." and
>"Exception No.2...shall not be required if located within 6 ft. of the
>premise wiring electrode."
>
>So you tell me, is your premise electrode located as close a practicable to
>the roof mounted array?  Again, this important decision will be left in the
>hands of the AHJ.
>
>In any case it appears that the intent of the Code is that a separate DC
>ground electrode conductor shall be run from the array frame to the
>additional electrode (or premise wiring electrode if determined to be in the
>practicable location).  Now, my understanding of this version of the Code is
>that the intent was that this GEC conductor would not have to be bonded to
>the other ground electrode systems on the premise. But it appears that in
>fact the Code ends up requiring that that this additional array ground
>system be bonded to the premise system.
>
>
>
>Mark Frye
>Berkeley Solar Electric Systems
>271 Vistamont Dr
>Grass Valley CA 95945
>(530) 401-8024
>www.berkeleysolar.com
>
>-----Original Message-----
>From: Ray Walters [mailto:walters at taosnet.com]
>Sent: Friday, June 13, 2008 3:41 AM
>To: RE-wrenches at topica.com
>Subject: 690.47 (was Enphase) [RE-wrenches]
>
>
>
>I had a question regarding the 2008 version of 690.47. It looks like a lot
>of changes occurred. 690.47 (D) seems to require a separate grounding
>electrode at the inverter and array if located more than 6 ft from the
>premises ground. But the wording is unclear to me: is this required? or does
>this section merely cover supplemental grounding if you choose to do so?
>690.47 also appears to have removed the limit on not having to use larger
>than #6 for the GEC. My read is that with a DC breaker rated at 250 amps, we
>would now have to use #4 if we were bonding to a UFER ground (250.166 (D)
>
>THanks for your clarification in advance,
>
>Ray Walters
>
>
>On Jun 12, 2008, at 11:00 PM, Bill Brooks wrote:
>
> >
> > The 2008 NEC allows sizing of combined GEC and EGC to be same size as
> > EGC in
> > 690.47(C) in an inverter with GFP. Whether it should be allowed or not
> > is another issue. In California, using the 2005 NEC, 8AWG is the
> > smallest GEC allowed.
> >
> > Bill.
> >
> > -----Original Message-----
> > From: Drake Chamberlin [mailto:Drake.Chamberlin at redwoodalliance.org]
> > Sent: Thursday, June 12, 2008 9:10 PM
> > To: RE-wrenches at topica.com
> > Subject: RE: Questions for Enphase Reps [RE-wrenches]
> >
> >
> > Hello Bill,
> >
> > At 06:27 PM 6/12/2008, you wrote:
> >> Depending on the version of the NEC your are using, it is possible to
> >> have
> > a
> >> combined dc GEC and ac EGC that is as small as 14 AWG
> >
> > I'm glad to get your confirmation about this.   Although this seems
> > to be accepted by our inspectors, I'm not sure why we are allowed to
> > have an GEC smaller than #8.  How does that work?
> >
> > Thanks,
> >
> > Drake
> >
> >
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>
>R. Walters
>Solarray.com
>NABCEP # 04170442
>
>
>
>
>--
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