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 <r...@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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