Do you need to go under the 2008 NEC or can you look at 2011? 2008 is
notorious for being confusing in this area.
*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *Jason Szumlanski
*Sent:* Monday, September 29, 2014 11:54 AM
*Subject:* Re: [RE-wrenches] PV Array Definition and 690.47(D) (2008)
We are 100% on the same page. That is the technique we use and the argument
I make. In a large proportion of cases we have modules directly above the
existing premises grounding electrode, or otherwise where an additional
grounding electrode would be "as close as practicable" to a location within
A 25MW plant presumably has several distinct structures on which it is
mounted. I can see the rationale for a GEC and electrode for each structure
in that scenario. But a single building with various roof faces is
technically a single mechanically integrated structure on which PV modules
On Mon, Sep 29, 2014 at 2:19 PM, Ray Walters <ray at solarray.com> wrote:
Definitely could use some clarification. The 690 definition of an array
says "mechanically integrated", which sort of implies each roof plane is
its own array.
However in terms of actual PV design terminology, each PV system has only
one array which may consist of many subarrays. Even a 25 MW plant has Only
So once again, NEC is inventing its own language that is not consistent
with actual terminology in use for over 30 years. (Ugh)
My call is that you would bond each subarray to each other with #6, and
then bring down a single GEC. Multiple GECs sounds very silly, but damn
that NEC language.
I would argue that "mechanically integrated" means they are all bolted down
to the same building (one support structure)
What other electrical system would require multiple GECs for an
installation on a single building ?
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
On 9/29/2014 6:21 AM, Jason Szumlanski wrote:
The definition of Array in 690.2 is ambiguous. Figure 690.1(A) seems to
indicate that groups of modules on different roof surfaces could be
considered a single array. The textual definition itself could be construed
either way. We have successfully argued that an entire roof mounted system
with modules on different roofs constitutes a single array. Therefore, if
the additional grounding electrode required by 690.47(D) qualifies for
Exception 2, it is not required. However, our "favorite" jurisdiction has
just interpreted it differently, requiring a separate electrode and
electrode conductor for each roof surface... and there are a lot of roof
surfaces on this particular job. Complying will not be fun or cheap.
How is your jurisdiction interpreting this?
Related note: Figure 690.1(A) would effectively make each module in a
microinverter based system a distinct array. The figure seems to imply that
all modules that form a PV Output Circuit are a single array. Each module
is a complete PV Output Circuit in a microinverter based system. It's
strange that the textual definition is concerned with mechanical
assemblies, but the figure refers to electrical configuration in defining
Array. In fact, in the text an Array is defined as components forming "a
direct-current power-producing unit." In a microinverter-based system, how
can any group of modules be considered an array given that definition?
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