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

Ray Walters ray at solarray.com
Mon Sep 29 11:19:13 PDT 2014


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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