Larry, Wrenches:
I appreciate your questions and comments. I think there is a broader question here: How do we differentiate between a perceived intent of the Code authors versus the actual language they provide in the Code? Many members of this forum have commented on the forum and to me off-line about the “intent” of the section. I find these discussions have academic value only. I could pretend to know what the intent of the framers of the code section, but how do I prove that intent to a plan checker? Here in the real world we all must deal with building officials who know how to read and can choose to apply that which is in black and white. Furthermore, building officials often refer to trade articles when justifying rulings—articles written by those perceived to be knowledgeable. As an example, referring back to the single point of connection discussion, the interpretation for the requirement for a single point is not mine alone. This article <https://iaeimagazine.org/magazine/2014/01/16/load-side-pv-connections/> in the IAEI newsletter agrees with the single-point interpretation. Articles like this makes it more difficult to argue that I know the “intent”. See excerpt below for a clear reading of the language: This section has been revised to specifically require that multiple inverters in a single PV system shall be connected to the existing premises wiring system at a *single* dedicated circuit breaker or fusible disconnecting means. This section no longer allows multiple connections to a load center or panelboard where there are multiple inverters involved. Multiple inverters must first be combined in an AC combining panel and the output of that panelboard is then connected to the single point of connection in the distribution equipment through one circuit breaker or fusible disconnecting means. See diagram 1. [image: https://iaeimagazine.org/images/2014_01/14a_WilesFig1.jpg] So I ask this forum: What evidence, other than the language in the 2017 code, can you offer me to take to my local building department that will prove to them that under the 2014 NEC the NFPA did not mean what they wrote in section 705.12(D)(1)? Thanks in advance. William Miller *From:* Starlight Solar Power Systems [mailto:la...@starlightsolar.com] *Sent:* Wednesday, February 27, 2019 9:22 AM *To:* will...@millersolar.com; RE-wrenches *Subject:* Re: [RE-wrenches] Multiple inverters 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 <will...@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:aug...@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 <will...@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. 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