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Thread: 690 or 705 sections that need changes for the 2020 NEC cycle?

  1. #1
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    690 or 705 sections that need changes for the 2020 NEC cycle?

    I’m going to the PV Industry Forum meeting in Golden, CO next week. Let me know if there is any particular changes you would like to see brought up. I have until the 30th to send in my list. I have my pet issues written up but I’m always looking for more. Keep them reasonable though, we are not going to get RSS removed for instance.

    I’m particularly interested in wording that is causing problems due to multiple interpretations between contractors, plan checkers, inspectors, etc that is throwing off projects.

  2. #2
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    Quote Originally Posted by pv_n00b View Post
    I’m going to the PV Industry Forum meeting in Golden, CO next week. Let me know if there is any particular changes you would like to see brought up. I have until the 30th to send in my list. I have my pet issues written up but I’m always looking for more. Keep them reasonable though, we are not going to get RSS removed for instance.

    I’m particularly interested in wording that is causing problems due to multiple interpretations between contractors, plan checkers, inspectors, etc that is throwing off projects.
    How about something that eliminates the de-facto requirement to include rounding errors when sizing AC combining panelboards, and allows for minuscule related loads in a dedicated PV system panelboard (DAS, AFCI power, TVSS, convenience outlet), without making a panelboard significantly larger than any real amount of current on it? If a panelboard is ultimately protected by an main OCPD, there's no reason to accumulate all those breaker round-up errors.

    For instance, consider 17 qty inverters with 18A operating current, and 25A breakers. 17*25A = 425A. However, if you neglect the fact that you had to round up to 25A breakers, you realize that only 306A worth of current are present in the first place, so all you really should need is 400A.

    I'm thinking something like a way to use the 120% rule in reverse, to allow for load breakers. Satisfying both of these criteria.
    A. 1.25* total inverter current <= busbar and main OCPD ampacities
    B. 1.25*total inverter current + sum of auxiliary load breakers <= 1.2 * busbar ampacity
    C. The locations of load breakers are such that load and source currents are in opposite directions on the busbar
    Last edited by Carultch; 03-27-17 at 11:02 PM.

  3. #3
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    I would like the NEC to declare one way or the other whether or not an AC disco on a supply side connected PV system needs a neutral to ground bond, with all that entails. Some AHJs say yes, others say no.

  4. #4
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    Quote Originally Posted by pv_n00b View Post
    I’m going to the PV Industry Forum meeting in Golden, CO next week. Let me know if there is any particular changes you would like to see brought up.
    Cool, thanks!
    How reasonable is this?
    Clearly require a fused PV disconnect which is accessible 24/7 within 10 feet of... (*outdoors*, this is)...
    the point where the service entrance conductors enter the structure. Period. Supply side, load side, whatever.

    And also make it clear that with a supply side connection, said fused outdoor PV disco switch = the PV system disconnect and also = the "point of interconnection".
    With a load side connection, I think said fused switch could also be called the same 2 things?

    Why have a PV combiner panel with OCPD in a basement, then run to an unfused switch outdoors (for POCO), then back into the basement to a fused service disco and j-box? ( https://www9.nationalgridus.com/non_...le_1line_B.pdf )

    And is there really any reason to put that j-box indoors?

    ----
    Here are some other thoughts, related and not:

    690.13 (for DC PV disco) says "readily accessible", how can something be that way when possibly locked inside a building?

    690.54 (for AC disco) drops the "readily" from accessible. Also, the title says "point" and the next sentence adds an s, "points". There's only 1 point.

    690.56 says "a permanent plaque", which is singular. So...where do you put that single plaque...at the service disconnecting means *or*... at the PV disco?

    705.31- the OCPD in the 1st sentence, the red part,... this is the OCPD or OCPDs for the inverter or inverters.
    The exception, I read it as-
    if none of these: inverter(s), AC PV combiner panel, or switch for AC PV combiner panel, are within 10 feet of....somewhere...put cable limiters or current-limited breakers...somewhere

    I think the cable limiters/c-l breakers would *become* the point of interconnection, but...no words as to where that might be.
    If the choices for "POI" are either: j-box or PV OCPD, the point of interconnection should be the service side of the PV OCPD, and the OCPD should be accessible 24/7 at the most obvious spot, that being the next to the outdoor meter if there is one.

    705.31 Location of Overcurrent Protection.
    Overcurrent protection for electric power production source conductors,

    connected to the supply side of the service disconnecting
    means in accordance with 705.12(A), shall be located
    within 3m (lOft) of the point where the electric power
    production source conductors are connected to the service.

    Exception: Where the overcurrent protection for the power
    production source is located more than 3m( 10') from the
    point of connection
    for the electric power production
    source to the service, cable limiters or current-limited circuit
    breakers for each ungrounded conductor shall be installed
    at the point where the electric power production
    conductors are connected to the service.

  5. #5
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    Quote Originally Posted by Carultch View Post
    For instance, consider 17 qty inverters with 18A operating current, and 25A breakers. 17*25A = 425A. However, if you neglect the fact that you had to round up to 25A breakers, you realize that only 306A worth of current are present in the first place, so all you really should need is 400A.

    I'm thinking something like a way to use the 120% rule in reverse, to allow for load breakers. Satisfying both of these criteria.
    A. 1.25* total inverter current <= busbar and main OCPD ampacities
    B. 1.25*total inverter current + sum of auxiliary load breakers <= 1.2 * busbar ampacity
    C. The locations of load breakers are such that load and source currents are in opposite directions on the busbar
    I would go for:

    The sum of 125% of the inverter(s) output circuit current and the ratings of all other
    overcurrent devices on a panelboard, excluding the rating of the overcurrent device
    protecting the busbar, shall not exceed the ampacity of the busbar.
    In your example above you'd have 383A of inverter current, which would allow you to have a 15A monitoring device breaker and still have a 400A panel.

    This is 705.12(B)(2)(3)(c) by the way.

  6. #6
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    My first candidate:

    705.12(B)(2)(2)

    Fix it so it can't be read to imply that the requirement is the sum of the inverter current plus the minimum tap conductor requirement.

  7. #7
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    Quote Originally Posted by jaggedben View Post
    I would go for:



    In your example above you'd have 383A of inverter current, which would allow you to have a 15A monitoring device breaker and still have a 400A panel.

    This is 705.12(B)(2)(3)(c) by the way.
    What if I fully saturate all 400A in a panelboard, with 10 qty inverters at 32A each?


    I'd like to have the possibility for PV-specific minimal amp loads in such a panel, as long as Kirchhoff's current law will maintain safe busbar operation.

  8. #8
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    Quote Originally Posted by jaggedben View Post
    My first candidate:

    705.12(B)(2)(2)

    Fix it so it can't be read to imply that the requirement is the sum of the inverter current plus the minimum tap conductor requirement.
    I'd like to see a 705 definition of "source tap" aka inverter tap... because it is different than tap as defined in 240.2.

    Then differentiate in 705.12(B)(2) requirements for source taps and any modification of 240.21(B) load tap requirements.
    I will have achieved my life's goal if I die with a smile on my face.

  9. #9
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    Quote Originally Posted by ggunn View Post
    I would like the NEC to declare one way or the other whether or not an AC disco on a supply side connected PV system needs a neutral to ground bond, with all that entails. Some AHJs say yes, others say no.
    I'll be there next week also. This is near the top of my list.

  10. #10
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    Quote Originally Posted by Carultch View Post
    What if I fully saturate all 400A in a panelboard, with 10 qty inverters at 32A each?
    I'd like to have the possibility for PV-specific minimal amp loads in such a panel, as long as Kirchhoff's current law will maintain safe busbar operation.
    My suggested language above was intended to be helpful towards your request to deal with rounding errors. This last post seems like a big expansion of the issue. Feel free to try to define 'PV-specific' and minimal amps in concise language. I think the CMP will be biased toward simpler rules.

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