[RE-wrenches] Multiple inverters

[August Goers]

Hi William,

I agree with Rebekah's response to you - I don't believe it was ever the
intention of the 2014 NEC to have only one OCPD allowed per site. Rather,
the language is trying to state that you need a dedicated breaker for your
inverter or group of microinverters. In other words, you can't tie an
inverter into a breaker that also feeds another device.

The article by John Wiles is very clearly contrasting this opinion, no
arguing there. I think his early interpretation of the 2014 NEC was just
plain off. He even mentioned that the definition of "PV system" is unclear
and up for AHJ interpretation. In less than a year we'll be under the 2017
NEC in California.

August


On Mon, Feb 25, 2019 at 9:45 PM William Miller <william at millersolar.com>
wrote:

> 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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