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    Help with multiple service disconnects and AC PV disco

    Following questions can also go under Grounding and Bonding or NEC forum but wrote it here because has new AC PV disco

    Attached sketch shows incoming serice conductors from utility 4#3/0 going into existing trough. The 4#3/0 service conductors get tapped to existing 100A serivce disco #1, existing 100A service disco #2 and new 150A AC PV Disco.

    Their is existing #4 GEC conductor from neutral bar of Service Disco #1 to neutral bar of Service Disco #2 which then goes to cold water pipe and ground rods. With addition of new AC 150A PV Disco #6 GEC is connected to #4 GEC as shown sketch. PV Disco has main bonding jumper. Please PV disco being service disco is not the discussion here. It has main bonding jumper and under NEC 2014.

    Following Questions:
    1. Being PV disco I was wondering does the install need to comply with NEC 2014 Article 250.64(D)?

    2. Does the grounding and bonding shown sketch comply with NEC 2014 Article 250.64(D)?

    3. Does the connection of new #6 GEC from PV disco to #4 GEC need to change to comply per NEC 2014 Article 250.64(D)? If yes then how so?

    4. Nec 2014 Article 250.64(D) says to comply with 250.64(D)(1), 250.64(D)(2), or 250.64(D)(3). Does word OR mean can have combination of D(1), D(2) or D(3) or just one of the three?


    AHJ is under NEC 2014 please only NEC 2014 nothing else.
    Attached Files

    #2
    Originally posted by hhsting View Post
    ..

    Following Questions:
    1. Being PV disco I was wondering does the install need to comply with NEC 2014 Article 250.64(D)?
    Ask your AHJ if they have an opinion. For a minute we thought the 2020 NEC was finally going to weigh in on this question but I just got my copy and it has nothing on grounding and bonding, so I guess they gave up on that part again. In my opinion there is nothing unsafe about what's shown in the sketch. You have grounding and an effective ground-fault-current path.

    2. Does the grounding and bonding shown sketch comply with NEC 2014 Article 250.64(D)?
    I believe so. The only questionable aspect is that the GEC tap from 100A disco#1 goes into disco#2 instead of being tapped outside to the main GEC. Pretty nitpicky item that probably makes no safety difference.

    3. Does the connection of new #6 GEC from PV disco to #4 GEC need to change to comply per NEC 2014 Article 250.64(D)?
    No.

    4. Nec 2014 Article 250.64(D) says to comply with 250.64(D)(1), 250.64(D)(2), or 250.64(D)(3). Does word OR mean can have combination of D(1), D(2) or D(3) or just one of the three?
    Good question I suppose. If you do (3) then you are done, there is absolutely no reason to do any part of (1) or (2), and since it would arguably run afoul of 250.6(A) I would say it should not be allowed. I see no real problem with combining aspects of (1) and (2), although perhaps for consistency's sake that shouldn't be allowed either. I don't really see the relevance to your sketch, since it is just (1) anyway, notwithstanding the nitpick noted above. Move the connection of the Disco #1 to the outside of the enclosures and you simply have compliance through (1). This is just my opinion, your AHJ's might differ.

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