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Commercial solar PV grounding with CT cabinet supply side connection

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    #16
    Originally posted by solarken View Post

    I ended up removing the CT cabinet from the design altogether, and replacing the service conductors between the utility and the main disconnect with heavier wire and one fewer parallel conductors, to free up a lug on the line side of the main disconnect for landing the solar. While moot for this project, I still would like to understand for future projects, If there is already a main bonding jumper in the main service disconnect to achieve the neutral to ground bond just like typical in all building services, and you come along and add solar, using a CT cabinet to provide the additional lugs for a line side tap, and inserted between the existing main disconnect and the utility, should the neutral in the CT cabinet also be bonded to the CT cabinet/ground as well? Specifically, there is already the main bonding jumper in the existing main disconnect, would adding a CT cabinet with a main bonding jumper installed there as well, so that there are two points where neutral is bonded to ground (in the main disconnect, and in the CT cabinet) violate any NEC requirement? Or should the bonding jumper be omitted from the added CT cabinet? The examples I have found for CT cabinet wiring have all been from utility side perspectives, where they owned the CT cabinet and it was out near the utility transformer, not on the customer premises, and they show the neutral to ground bond. In my case, I would have installed the Ct cabinet as customer-premise equipment, with no EGC between the CT cabinet and the utility-owned equipment. Thanks.
    As of now there are two ways to do it and usually the AHJ decides which they prefer. You can treat the line side connection as a separate service, where you bond N to G in the PV disco, any enclosures between the disco and the service conductors are bonded to N, and there is no EGC back to the service from the PV AC disco but an external bond between G on the PV side and building G, i.e., the way CPS in San Antonio wants it. Or you can treat it like any other PV interconnection, where you do not bond N to G in the PV disco and there is an EGC all the way back to the service, i.e., the way most of the other AHJ's in Texas want it.

    I was told that the 2020 NEC would take a stand on the issue and direct it to be one way or the other, but rumor has it (I have not yet seen a copy of the 2020 NEC) that the committee writing that section of the code has backed away from it.

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