[RE-wrenches] Multiple inverters
Christopher Warfel
cwarfel at entech-engineering.com
Wed Feb 27 16:48:49 EST 2019
The original question was w/r to:**/The source interconnection of one or
more inverters installed in one system shall be made at a dedicated
circuit breaker or fusible disconnecting means./
and whether one disconnect could be used to disconnect multiple
inverters. The inference as I read it was that there was no other
disconnect means for the inverters in question.
If you use an AC combiner upstream of the disconnecting means with
individual OCPDs as required, then you have your individual
disconnection and that is required and has been practiced for many code
cycles. A circuit breaker OCPD is a code compliant disconnecting means.
I cannot imagine anyone using an AC combiner method and not using OCPDc.
Using a disconnecting means to then disconnect downstream AFTER an AC
combiner is of course allowed. Chris Warfel
/
/
On 2/27/2019 1:48 PM, William Miller wrote:
>
> Chris:
>
> The 2014 code would require individual disconnecting means prior to
> aggregation, i.e. an AC combiner. Therefore your scenario would not
> exist.
>
> Wm
>
> *From:*RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org
> <mailto:re-wrenches-bounces at lists.re-wrenches.org>] *On Behalf Of
> *Christopher Warfel
> *Sent:* Wednesday, February 27, 2019 10:43 AM
> *To:* re-wrenches at lists.re-wrenches.org
> <mailto:re-wrenches at lists.re-wrenches.org>
> *Subject:* Re: [RE-wrenches] Multiple inverters
>
> I know I keep popping up on this, but 2014 makes no sense if it is
> saying to connect multiple inverters to one disconnect. It would be
> difficult and dangerous to take one out of service for any reason
> including replacement. I would that that you'd have to shut down all
> the inverters just to replace one. Some of the large
> commercial/industrial/utility systems have hundreds of inverters and
> there is no way they would install a system to this interpretation of
> the NEC.
>
> On 2/27/2019 12:22 PM, Starlight Solar Power Systems wrote:
>
> William,
>
> It seems this question needs to be addressed: What is the intended
> meaning of “installed in one system” in 2014? If you have separate
> “systems”, they should not be governed by 705.12. So, at what
> point does a “system” begin and end? PV modules to the disconnect?
> ...to the load panel? ...to the service entrance?
>
> Larry
>
> On Feb 25, 2019, at 10:42 PM, William Miller
> <william at millersolar.com <mailto: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
> <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:
>
> <image001.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 <mailto: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.
>
> Thisarticle
> <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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