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Thread: Line Side tap, but not really?

  1. #1
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    Line Side tap, but not really?

    I have a question for you all about PV system interconnection. It’s a bit of anodd one.

    Thereis a pedestal at the road with a meter and 200a disconnect and a small bus forload breakers. Currently temp power is being pulled off of that load bus,but in the future there will be no loads out at the pedestal. Anunderground run will go from the pedestal to a 200a main panel with main breakerinside the garage.


    The PV system to be installed there would be protected by60A OCPD. This is too much to interconnect with a breaker (120% rule=> 40A), so we will need to connect upstream of the main breaker. Normally, I would do this with taps in the main panel in the garageline side to the main breaker. This is technically a load side connectionsince there is a primary disconnect at the pedestal, but is allowedbecause the bus is protected by the 200a main.

    The odd part on this oneis the load buss out at the road. If somebody were to install 4king-sized hot-tubs in the street and run them all at once during the day whilethe solar was at peak production, they could theoretically overload the bus inthe pedestal service panel with 60A from solar and 200A from the utility. Can I proceed as logic and reason suggest—continue with taps in garage panel—orwould you all suggest something else?

    Thanks....

  2. #2
    Join Date
    Dec 2012
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    Is the only GES-Neutral bond at the pedestal, and does POCO consider that to be the service disconnect? If so you would be technically in violation, but it would not IMHO be unsafe.
    The key point, I think, is how the AHJ will react. You might have to put a placard in the disconnect prohibiting adding load breakers.
    A sufficiently anal inspector might also require upsizing the feeder wires if the 86% allowance was used to size them, since at times the feeder would no longer be carrying the entire dwelling load.

  3. #3
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    Quote Originally Posted by GoldDigger View Post
    Is the only GES-Neutral bond at the pedestal, and does POCO consider that to be the service disconnect? If so you would be technically in violation, but it would not IMHO be unsafe.
    The key point, I think, is how the AHJ will react. You might have to put a placard in the disconnect prohibiting adding load breakers.
    A sufficiently anal inspector might also require upsizing the feeder wires if the 86% allowance was used to size them, since at times the feeder would no longer be carrying the entire dwelling load.
    Yes and Yes. Bond is at the ped and POCO considers it the first means/ Service Disco.

    I think I may try talking an inspector? Would you suggest that I offer a compromise to upsize the feeders not using the 86% (ie run 250mcm Al instead of 4/0 Al) and make the placard (perhaps even remove the breaker placement bar in the ped, so additional breakers CAN'T be installed)?

    I don't think its unsafe either, but we have no idea what an HO might do in the future and the harder I can make it to install load breakers at the ped, the better my case. Thank you very much.

    (Edit: usage, punctuation)
    Last edited by wrobotronic; 05-04-18 at 05:48 PM.

  4. #4
    Join Date
    May 2011
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    I'm confused about the pedestal equipment and the relationship of the small load bus to the feeder. Is it a feed-through lug design? Is the 200A disconnect on the line side or load side of that bus? How will the 200A feeder be connected to that equipment? The details are important. Got a pic of the diagram on that panel label?

  5. #5
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    The only NEC option I see would be to replace the pedestal with a stand-alone service disconnect/OCPD with no distribution. Reduce the service OCPD to 175A, that would give you 65A of back feed available to the PV system. This assumes the customer does not need the full 200A service.

  6. #6
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    Quote Originally Posted by pv_n00b View Post
    The only NEC option I see would be to replace the pedestal with a stand-alone service disconnect/OCPD with no distribution. Reduce the service OCPD to 175A, that would give you 65A of back feed available to the PV system. This assumes the customer does not need the full 200A service.
    If the pedestal is replaced with a simple service disconnect/OCPD, then the feeder can be tapped ahead of the main breaker at the garage for up to 200A, if on the 2014 or 2017 NEC.

  7. #7
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    Cherry Valley NY, Seattle, WA
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    Quote Originally Posted by jaggedben View Post
    If the pedestal is replaced with a simple service disconnect/OCPD, then the feeder can be tapped ahead of the main breaker at the garage for up to 200A, if on the 2014 or 2017 NEC.
    Wouldn't the feeder ampacity have to be at least the sum of the feeder ocpd plus 125% inverter current per 705.12 (D)(2)?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  8. #8
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    Quote Originally Posted by electrofelon View Post
    Wouldn't the feeder ampacity have to be at least the sum of the feeder ocpd plus 125% inverter current per 705.12 (D)(2)?
    No, because there's a downstream OCPD. See 705.12(D)(2)(1)(b).

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