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Connecting PV to an existing MLO service panel

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    Connecting PV to an existing MLO service panel

    Hello All,
    (Under NEC 2014) Would a PV connection (via a PV breaker) to an existing MLO panel considered a supply side connection? (To me it's a load side connection because the PV breaker takes one of the MLO panel's feeder breaker slots)
    And if it's not a supply side connection, would this following configuration comply with 705.12(D)(2)(3)(a)?
    48A output inverter connects to a 100A MLO panel via a 60A PV breaker.
    125% x 48A + 0A <=100A.
    Assumptions:
    - Manufacturer cutsheet of that MLO panel allows PV system to connect to the panel via a PV breaker.
    - the total breakers (PV breaker plus all existing feeder breakers) are no greater than 6.

    Also, if it's a load side connection, is there any of the 705.12 section requires the service panel has to have a main breaker in order for the PV system to hook up? I see that NEC 2014 705.22 only requires a disconnect device at the main service panel, not a OCPD. Meaning an external disconnect ahead of the MLO panel would suffice.
    Thanks.
    Last edited by fandi; 01-08-19, 05:43 PM.

    #2
    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.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

    Comment


      #3
      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.
      Can you explain why is that a supply side connection? Thx.

      Comment


        #4
        I think anything ahead of the meter is considered supply side. And anything after the meter is considered load side.

        Comment


          #5
          Originally posted by fandi View Post
          Can you explain why is that a supply side connection? Thx.
          Read 705.12(A), 230.82(6), and the article 100 definition of "service conductors".
          Ethan Brush - East West Electric. NY, WA. MA

          "You can't generalize"

          Comment


            #6
            Originally posted by electrofelon View Post
            Read 705.12(A), 230.82(6), and the article 100 definition of "service conductors".
            So per this attached diagram, the only difference between supply side vs load side configurations is the presence of the main breaker? (because other than that, they're the same)
            Click image for larger version

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            Comment


              #7
              Simply, if there is no other disconnecting means between the service point and the PV disconnecting means, then it is not connected on the load side of a service disconnecting means. If it is not load side then it is supply-side.

              Meters have nothing to do with it as far as the NEC is concerned.

              Comment


                #8
                Originally posted by jaggedben View Post
                Simply, if there is no other disconnecting means between the service point and the PV disconnecting means, then it is not connected on the load side of a service disconnecting means. If it is not load side then it is supply-side.

                Meters have nothing to do with it as far as the NEC is concerned.
                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.
                Last edited by fandi; 01-08-19, 07:58 PM.

                Comment


                  #9
                  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?
                  I think Jaggadben explained it very clearly. Perhaps its a "small" difference having a main breaker in there, but that is the service disconnect and the Pv is on the load side of the service disconnect.
                  Ethan Brush - East West Electric. NY, WA. MA

                  "You can't generalize"

                  Comment


                    #10
                    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.
                    see 705.12(A) and (D). I admit it is not very logically laid out.
                    Ethan Brush - East West Electric. NY, WA. MA

                    "You can't generalize"

                    Comment


                      #11
                      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.

                      Comment


                        #12
                        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.

                        Comment


                          #13
                          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

                          Comment


                            #14
                            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"

                            Comment


                              #15
                              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"

                              Comment

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