690.47 (was Enphase) [RE-wrenches]

[Mark Frye]

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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