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Thread: Connecting PV to an existing MLO service panel

  1. #11
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    Quote Originally Posted by electrofelon View Post
    Yes it is a supply side connection. It is a bit odd that the 120% rule doesnt apply in that situation. I wonder if that was an oversight by the code makers.
    The 120% rule cannot apply because there is no OCPD on the panel. There is nothing to base the calculation on because the available current to the bus from the utility side is virtually unlimited.

  2. #12
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    Quote Originally Posted by fandi View Post
    I agree that meters have nothing to do in this case, but I try to find in the Art 100 about the definitions of 'supply side connection' and 'load side connection' and I can't find them. As you can see in my diagram, the PV connection point is still the same spot. So how do we know when will be supply side connection, and when will be load side connection? And just like your interpretation, the Code needs to make it clear in Art 100 that a connection of the load side of the main breaker is considered load side connection.
    Article doesn't really need to make that clear when 705.12(A) states things pretty precisely.

    I forget if Article 100 defines the service disconnecting means, or just service equipment, but read Article 230 for more in the disconnecting means.

  3. #13
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    The 120% rule applies to situations where the current to the bus or conductor from each source is limited and so the bus/conductor is protected. Adding the two current sources would allow a load to draw more current and defeat the protection.
    Service conductors are NOT protected, so adding more current from PV will not make things worse. So no 120% rule.
    That lack of protection is why service conductors are not allowed to run very far inside.

    Sent from my XT1585 using Tapatalk

  4. #14
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    Quote Originally Posted by ggunn View Post
    The 120% rule cannot apply because there is no OCPD on the panel. There is nothing to base the calculation on because the available current to the bus from the utility side is virtually unlimited.
    I should have been able to figure that one out. yesterday was a long day....
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  5. #15
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    Quote Originally Posted by fandi View Post
    I agree that meters have nothing to do in this case, but I try to find in the Art 100 about the definitions of 'supply side connection' and 'load side connection' and I can't find them. As you can see in my diagram, the PV connection point is still the same spot. So how do we know when will be supply side connection, and when will be load side connection? And just like your interpretation, the Code needs to make it clear in Art 100 that a connection of the load side of the main breaker is considered load side connection.
    For what its worth, here is a bit on supply side connections by the Washington State Labor and Industries:

    https://www.lni.wa.gov/TradesLicensi...ts/Elc1410.pdf
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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