Hi Jason,
Do you need to go under the 2008 NEC or can you look at 2011? 2008 is notorious for being confusing in this area. Best, August *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Jason Szumlanski *Sent:* Monday, September 29, 2014 11:54 AM *To:* RE-wrenches *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 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 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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