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Thread: 240 delta with high leg solar installation

  1. #81
    Join Date
    Jun 2006
    Location
    Ohio
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    20,482
    Quote Originally Posted by PVfarmer View Post
    ...
    The OP described the PV neutral as ending at the PV disco, but also continuing on as a GEC thru the xfmr to the MSP.

    There should be a bonding jumper in the PV disco *and* the MSP, and both ground bars (MSP/PV disco) should be connected to the GES by GECs.
    That isn't how it was described.
    I don't even understand how the "GEC goes thru the PV xfmr" as described...



    Bus A-N is 120V, and bus C-N is 120V.
    I'm assuming that they are being used. Won't that throw off the inverter's reference somehow?
    ...
    A neutral conductor is run between transformer H0 and PV disconnect neutral. If the 480/277 SDS GEC lands in the PV disconnect, that is where the system bonding jumper is also located. A supply-side bonding jumper is required from the PV disconnect to the transformer non-current-carrying metal parts (NCCMP). An EGC is required to be run with the primary (utility side) conductors. It bonds MSP EGS to the transformer NCCMP. I believe the OPer is just taking the SSBJ and EGC as a GEC from PV to MSP. The conductors have different names... but they don't know that.

    A-N and C-N will not through off the inverter's [voltage] reference under normal operation. Only under a fault or non-compliant condition could they do so.
    I'll never get there. No matter where I go, I'm always here.

  2. #82
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
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    7,665
    Quote Originally Posted by PVfarmer View Post
    The step-down PV xfmr isn't a source- if there was no service of any kind, the inverters wouldn't run.
    I don't know if I'd call the grid a source- isn't it more of a...repository?
    The inverters need to know the impedance of the grid.
    No, they don't. All the inverters need is a transformer or a series of them between them and the MV lines that have a high enough kVA rating to handle their output. The only voltages they care about are those which appear at their terminals. If the voltages are within their tolerance and the transformer(s) is/are hefty enough, the inverter will connect and run. It really is that simple.

    Seriously, a bit of self education on how transformers work would do you a world of good and keep you from being so easily mystified.

  3. #83
    Join Date
    May 2017
    Location
    Brentwood, CA , US
    Posts
    8
    Just to clarify.... We have other installation with the exact same configuration and the work just fine. Also went over the design with SolarEdge and got their approval before plans were even drawn up. Sorry it took so long for me to reply..I got buried on a job.

  4. #84
    Join Date
    Jun 2015
    Location
    Newport County, Rhode Island, USA
    Posts
    621
    Quote Originally Posted by ggunn View Post
    The only voltages they care about are those which appear at their terminals.
    Wrong.

    Conventional generators are considered to be voltage sources as they provide constant ac voltages controlled by excitation systems. In contrast, a grid-tied inverter-based PV plant is
    modeled as a current source whereby the plant’s terminal voltage is dependent on the feeder.
    https://solectria.com//site/assets/f..._pv_plants.pdf

  5. #85
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
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    7,665
    Quote Originally Posted by PVfarmer View Post
    Wrong.

    Conventional generators are considered to be voltage sources as they provide constant ac voltages controlled by excitation systems. In contrast, a grid-tied inverter-based PV plant is
    modeled as a current source whereby the plant’s terminal voltage is dependent on the feeder.
    https://solectria.com//site/assets/f..._pv_plants.pdf
    Once more you are quoting out of context. I give up trying to explain to you how this stuff works. Once more I will point out that my knowledge is based on a degree in electrical engineering, 25 years as a practicing PE, and 8 years designing PV systems - several of which are connected to lower voltage services through transformers. I don't know everything but I know a lot.

    I have no idea what your experience in PV is, but judging from your comments it appears to me to be something less than mine. My advice to you is to spend more time actually working in PV and less lurking in here trying to show how everyone else is wrong. If you have just been trolling, then congratulations, you got me to slap the tar baby.

    Good luck to you; I'm done.

  6. #86
    Join Date
    May 2011
    Posts
    3,553
    Quote Originally Posted by BenJChaney View Post
    Just to clarify.... We have other installation with the exact same configuration and the work just fine. Also went over the design with SolarEdge and got their approval before plans were even drawn up. Sorry it took so long for me to reply..I got buried on a job.
    Curious if you've worked it out with the inspector. As you can see from this thread, he's not the only one who may need some explanation as to how this stuff works. Hope all the extra posts are at least somewhat helpful.

  7. #87
    Join Date
    Jun 2015
    Location
    Newport County, Rhode Island, USA
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    621
    Quote Originally Posted by BenJChaney View Post
    Just to clarify.... We have other installation with the exact same configuration and the work just fine. Also went over the design with SolarEdge and got their approval before plans were even drawn up. Sorry it took so long for me to reply..I got buried on a job.
    Thanks for hanging in there with this!

    What is the inspector's beef exactly? You said the below, and that he says there's a "missing neutral"?
    Aren't there signed permits or tests for the other installations you could show the wayward inspector?

    I can't see how one random city inspector would be privy to info that your particular POCO and engineers as well as SolarEdge aren't.

    "the city inspector is saying it won't pass because if there was a fault to ground on the primary side of the transformer it would not trip the breaker."

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