Discussion:
PV Array Definition and 690.47(D) (2008)
(too old to reply)
Jason Szumlanski
2014-09-29 12:21:04 UTC
Permalink
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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Ray Walters
2014-09-29 18:19:13 UTC
Permalink
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
Post by Jason Szumlanski
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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Jason Szumlanski
2014-09-29 18:53:38 UTC
Permalink
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
Post by Ray Walters
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
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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August Goers
2014-09-29 18:56:45 UTC
Permalink
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-bounces at 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 <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 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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Jason Szumlanski
2014-09-29 19:16:49 UTC
Permalink
Yeah, Florida is in the dark ages of solar in more ways than one. We're on
2008 still.

One area enlightened/progressive jurisdiction has eliminated the additional
electrode requirement altogether in light of the 2011 code cycle taking
effect soon. The one I am dealing with is notorious for making permitting
(in general) a living hell.


Jason
Post by August Goers
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-bounces at 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
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
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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