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Thread: PV plan check

  1. #21
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    Quote Originally Posted by cowboyjwc View Post
    Ok if you really read that section it only talks about the location of the solar breaker, also if you have a 200 panel + 90 amps of solar + everything else I'm guessing that 90% of the time you are going to exceed the busbar rating. Now if you go with one of the new solar panels with the 225 amp bus and a 150 amp main, the amount of solar you can put in is almost unlimited, to a point of course.
    That subsection states, in part, "The sum of the ampere ratings of all overcurrent devices on panelboards, both load and supply devices, excluding the rating of the overcurrent device protecting the busbar, shall not exceed the ampacity of the busbar." The underlined part is the MCB. Load device are load breakers. Supply devices is subjective. I believe there's somewhere that states you can use 125% of inverter output rating(s) for upstream determinations... anyone?
    I will have achieved my life's goal if I die with a smile on my face.

  2. #22
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    Quote Originally Posted by Smart $ View Post
    That subsection states, in part, "The sum of the ampere ratings of all overcurrent devices on panelboards, both load and supply devices, excluding the rating of the overcurrent device protecting the busbar, shall not exceed the ampacity of the busbar." The underlined part is the MCB. Load device are load breakers. Supply devices is subjective. I believe there's somewhere that states you can use 125% of inverter output rating(s) for upstream determinations... anyone?
    The way it's written you use 125% of the inverter nameplate rating for 705.12(D)(2)(3)(b) but the solar breaker rating for 705.12(D)(2)(3)(c). Of course, you can use different sections for different panels in series.

  3. #23
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    Quote Originally Posted by cowboyjwc View Post
    705.12(D)(2)(3)(b) says exactly what I said. Where two sources, one utility and the other an inverter, are located at opposite ends of the busbar that contains loads, the sum of 125% of the inverter output circuit current and the rating of the overcurrent device protection the busbar shall not exceed 120% of the ampacity of the busbar.

    We only have all in one panels here so the main service panel will always contain loads.
    Sorry, I misunderstood. I thought thought there was only one panel, the service panel with 400 bus with a 200 amp main breaker

    But I still dispute that that is "exactly" what you said. You left out the "ampacity of the busbar" part sorry to nitpick, but that made it seem you were interpreting the rule differently.
    Last edited by electrofelon; 09-20-17 at 07:52 PM.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #24
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    Quote Originally Posted by electrofelon View Post
    Sorry, I misunderstood. I thought thought there was only one panel, the service panel with 400 bus with a 200 amp main breaker

    But I still dispute that that is "exactly" what you said. You left out the "ampacity of the busbar" part sorry to nitpick, but that made it seem you were interpreting the rule differently.
    Oh you can nitpick all you want, I'm married with children. No what I have is a 200 amp panel with a 200 amp bus bar feeding a 400 amp panel.

    Or to reexplain it in solar terms, solar array to inverters, inverters to 90 amp solar breaker in a 400 amp panel with a 200 feeder, to a 200 amp main service panel/load center with a 200 amp bus.
    I can build anything you want if you draw a picture of it on the back of a big enough check.

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  5. #25
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    Cowboy,
    Maybe I am missing something. Why don't these folks just add a new meter for the solar?

  6. #26
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    Quote Originally Posted by Sierrasparky View Post
    Cowboy,
    Maybe I am missing something. Why don't these folks just add a new meter for the solar?
    POCO may not be willing to add another meter, especially if the state has Net Metering laws.

  7. #27
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    Quote Originally Posted by GoldDigger View Post
    POCO may not be willing to add another meter, especially if the state has Net Metering laws.
    Cowboy is in Southern CA.
    To the best of my recollection the POCO there will allow a separate meter.

  8. #28
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    Even if the utility allows it without extra fees and charges, which I doubt, adding another meter is a huge extra expense compared to a load side connection.

    Also Cowboy mentioned batteries and if the intention is to island with solar power to when the grid goes down, that ain't gonna work if the power and loads are on separate meters.

  9. #29
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    Quote Originally Posted by cowboyjwc View Post
    Oh you can nitpick all you want, I'm married with children. No what I have is a 200 amp panel with a 200 amp bus bar feeding a 400 amp panel.

    Or to reexplain it in solar terms, solar array to inverters, inverters to 90 amp solar breaker in a 400 amp panel with a 200 feeder, to a 200 amp main service panel/load center with a 200 amp bus.
    (2) Bus or Conductor Ampere Rating. One hundred twentyfive percent of the power source output
    circuit current shall be used in ampacity calculations for the following:
    (1) Feeders. Where the power source output connection is made to a feeder at a location other than the opposite end of the feeder from the primary source overcurrent device, that portion of the feeder on the load side of the power source output connection shall be protected by one of the
    following:
    a. The feeder ampacity shall be not less than the sum of the primary source overcurrent device and 125 percent of the power source output circuit current.

    200A primary source overcurrent device in 200a panel feeding 400 a panel with 200 amp feeder(250 ser al??? 3/0 cu thhwn? ????) 400 amp panel has 90a PV source(125% of output circuit) Yes?????
    would that make the feeder required to be rated @ 290 amps??? Just thinking outside the box in this unusual circumstance.
    CircuitRyder --- Unfortunately not all good ideas are code enforceable.

  10. #30
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    Quote Originally Posted by mwm1752 View Post
    (2) Bus or Conductor Ampere Rating. ....
    That's from the 2011 edition. He's under the 2014 NEC I believe and the changes have some significant requirement impact.
    I will have achieved my life's goal if I die with a smile on my face.

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