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 One array!
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 ?
Good Luck,
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
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?
Jason Szumlanski
Fafco Solar
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