[RE-wrenches] PV Array Definition and 690.47(D) (2008)

[Jason Szumlanski]

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
6 feet.

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
are mounted.


Jason Szumlanski

Fafco Solar


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
> 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 Engineer303 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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