[RE-wrenches] Multiple inverters

[William Miller]

August:



The 2014 code, which the AHJ for this project is using, states the
following:



(*1) Dedicated Overcurrent and Disconnect. The source*

*interconnection of one or more inverters installed in one*

*system shall be made at a dedicated circuit breaker or fusible*

*disconnecting means.*



Note that the language says, “The source interconnection…” (singular), and
“at a dedicated circuit breaker…”(again singular).  This makes it obvious
to me that the language says that the outputs of multiple inverters need to
be aggregated and connected via *one* OCPD.  I think the other wrenches
missed this point.



Your input is valuable by contrasting the language of the 2014 code with
that of the 2017 version.  The inclusion of the phrase “Each source…” in
the 2017 code completely changes the meaning.  Some AHJs will look to
future code versions for clarity even if they are not yet adopted.  I think
this is a good thing, and I really appreciate you bringing up the new
language.



The article from AEIA magazine ratifies the conclusion I drew from the 2014
code.  Fortunately the AHJ is misinterpreting the section to allow the more
liberal interpretation, the one that the 2017 code reflects.  I find it
best to contact the plan checker directly, which I did, and we are approved
for multiple OCPDs.  By the way, I think that article is well written and I
have book marked it.



I don’t know if the 2014 language was a mistake corrected in 2107, or what
the thinking was of the authors.  Regardless, we live by the language, not
the intent.



Thank you as well to all who responded.



William Miller









*From:* August Goers [mailto:august at luminalt.com]
*Sent:* Monday, February 25, 2019 9:07 AM
*To:* William Miller; RE-wrenches
*Subject:* Re: [RE-wrenches] Multiple inverters



Hi William -



In this case, it is helpful to look forward to the 2017 NEC for guidance:



[image: image.png]



I believe it's perfectly fine to have multiple inverter breakers in your
main.



August

Luminalt





On Mon, Feb 25, 2019 at 8:42 AM William Miller <william at millersolar.com>
wrote:

Friends:



I have an NEC code question on an upcoming project.  It is a home that has
an existing 8 kW ground-mounted grid-tied system.  The owner wants to add
another 10 kW of grid-tied PV.  My question is about 705.12, point of
connection.  Specifically section (D)(1).  That section states:



*The source interconnection of one or more inverters installed in one
system shall be made at a dedicated circuit breaker or fusible
disconnecting means.*



So if there are going to be two inverters on premise, do the outputs have
to be aggregated to connect via one circuit breaker?  This might be
difficult to do as the exiting inverter is connected via a different
sub-panel than the one that is planned to receive the new inverter output.



This article
<https://iaeimagazine.org/magazine/2014/01/16/load-side-pv-connections/>
addresses the question.



I would be very grateful if any of you can share any experience you might
have in interpreting this section of the code.



Thanks in advance.



William



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