Chapter 7 Special Conditions
ARTICLE 705 Interconnected Electric Power Production Sources
I. General
705.12 Point of Connection.
705.12(D):
(D) Utility-Interactive Inverters. The output of a utility-interactive inverter shall be permitted to be connected to the load side of the service disconnecting means of the other source(s) at any distribution equipment on the premises. Where distribution equipment including switchboards and panelboards is fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters, and where this distribution equipment is capable of supplying multiple branch circuits or feeders or both, the interconnecting provisions for the utility-interactive inverter(s) shall comply with (D)(1) through (D)(7)
(1) Dedicated Overcurrent and Disconnect. Each source interconnection shall be made at a dedicated circuit breaker or fusible disconnecting means.
(2) Bus or Conductor Rating. The sum of the ampere ratings of overcurrent devices in circuits supplying power to a busbar or conductor shall not exceed 120 percent of the rating of the busbar or conductor.
Exception: Where the photovoltaic system has an energy storage device to allow stand-alone operation of loads, the value used in the calculation of bus or conductor loading shall be 125 percent of the rated utility-interactive current from the inverter instead of the rating of the overcurrent device between the inverter and the bus or conductor.
HANDBOOK COMMENTARY:
The exception to 705.12(D)(2) permits an alternative to determining the load supplied by the bus or conductor. For example, because the inverter is capable of supplying only 30 amps of utility-interactive current to the panel and to the utility grid, it is safe to allow 125 percent of the continuous inverter backfeed current, which is 37.5 amps (1.25 ? 30), to be used in the 705.12(D)(2) calculation rather than the rating of the required load breaker determined by the main requirement.
(3) Ground-Fault Protection. The interconnection point shall be on the line side of all ground-fault protection equipment.
Exception: Connection shall be permitted to be made to the load side of ground-fault protection, provided that there is ground-fault protection for equipment from all ground-fault current sources. Ground-fault protection devices used with supplies connected to the load-side terminals shall be identified and listed as suitable for backfeeding.
(4) Marking. Equipment containing overcurrent devices in circuits supplying power to a busbar or conductor supplied from multiple sources shall be marked to indicate the presence of all sources.
(5) Suitable for Backfeed. Circuit breakers, if backfed, shall be suitable for such operation.
Informational Note: Circuit breakers that are marked “Line” and “Load” have been evaluated only in the direction marked. Circuit breakers without “Line” and “Load” have been evaluated in both directions.
(6) Fastening. Listed plug-in-type circuit breakers backfed from utility-interactive inverters that are listed and identified as interactive shall be permitted to omit the additional fastener normally required by 408.36(D) for such applications.
(7) Inverter Output Connection. Unless the panelboard is rated not less than the sum of the ampere ratings of all overcurrent devices supplying it, a connection in a panelboard shall be positioned at the opposite (load) end from the input feeder location or main circuit location. The bus or conductor rating shall be sized for the loads connected in accordance with Article 220. In systems with panelboards connected in series, the rating of the first overcurrent device directly connected to the output of a utility-interactive inverter(s) shall be used in the calculations for all busbars and conductors. A permanent warning label shall be applied to the distribution equipment with the following or equivalent wording:
WARNING
INVERTER OUTPUT CONNECTION
DO NOT RELOCATE THIS OVERCURRENT DEVICE