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Home My WebLink AboutPV Electrical Review Bulleten 060817 Frank DeMarco Harry Kim Director Mayor Allan Simeon Wil Okabe Deputy Director Managing Director County of Hawai‘i DEPARTMENT OF PUBLIC WORKS Aupuni Center 101 Pauahi Street, Suite 7 · Hilo, Hawai‘i 96720-4224 (808) 961-8321 · Fax (808) 961-8630 www.co.hawaii.hi.us Date: June 8, 2017 Code/ Edition: 2008 National Electric Code (NEC) Subject: PV Electrical Review The following is a list of design requirements that are most easily overlooked in the design phase. A) Ambient Conditions 1) Module Open Circuit Voltage – NEC 690.7 i) The open circuit voltage listed on the manufacturer’s specification sheet is only valid for the standard test conditions. When the temperature decreases, the module voltage increases, this increase poses the greatest issue with maximum string lengths, and maximum voltage input on the inverter. As the temperature increases, the module voltage decreases, and may not create a high enough voltage to turn on the inverter. 2) Rooftop conductor de-rate – NEC Table 310.15(B)(2)(c) i) Depending on the conduit height above the roof, the conductors will be subject to a de-rate. 3) Conduit Expansion – NEC Table 352.44 i) PVC conduit subject to a change in temperature will expand and contract as the temperature changes. B) Warning Labels 1) Labels and Marking - NEC 690.5(C) WARNING ELECTRIC SHOCK HAZARD IF A GROUND FAULT IS INDICATED NORMALLY GROUNDED CONDUCTORS MAY BE UNGROUNDED AND ENERGIZED 2) Bipolar Source and Output Circuits – NEC 690.7(E) County of Hawai‘i is an Equal Opportunity Provider and Employer. WARNING BIPOLAR PHOTOVOLTAIC ARRAY. DISCONNECTION OF NEUTRAL OR GROUNDED CONDUCTORS MAY RESULT IN OVERVOLTAGE ON ARRAY OR INVERTER. 3) Single 120-Volt Supply – NEC 690.10(C) WARNING SINGLE 120-VOLT SUPPLY. DO NOT CONNECT MULTIWIRE BRANCH CIRCUITS! 4) Switch or Circuit Breaker – NEC 690.17 WARNING ELECTRIC SHOCK HAZARD. DO NOT TOUCH TERMINALS. TERMINALS ON BOTH THE LINE AND LOAD SIDES MAY BE ENERGIZED IN THE OPEN POSITION. 5) Ungrounded Photovoltaic Power Systems – NEC 690.35(F) WARNING ELECTRIC SHOCK HAZARD. THE DC CONDUCTORS OF THIS PHOTOVOLTAIC SYSTEM ARE UNGROUNDED AND MAY BE ENERGIZED. 6) Modules – NEC 690.51 i) Modules shall be marked with identification of terminals or leads as to polarity, maximum overcurrent device rating for module protection, and with the following ratings: (1) Open-circuit voltage (2) Operating voltage (3) Maximum permissible system voltage (4) Operating current (5) Short-circuit current (6) Maximum power 7) Alternating-Current Photovoltaic Modules – NEC 690.52 i) Alternating-current modules shall be marked with identification of terminals or leads and with identification of the following ratings: (1) Nominal operating ac voltage (2) Nominal operating frequency (3) Maximum ac power (4) Maximum ac current (5) Maximum overcurrent device rating for ac module protection 8) Direct Current Photovoltaic Power Source – NEC 690.53 i) A permanent label for the direct-current photovoltaic power source indicating items (1) through (5) shall be provided by the installer at the photovoltaic disconnecting means: (1) Rated maximum power-point current County of Hawai`i is an Equal Opportunity Provider and Employer. (2) Rated maximum power-point voltage (3) Maximum system voltage (4) Short-circuit current (5) Maximum rated output current of the charge controller (if installed) 9) Interactive System Point of Interconnection. All interactive system(s) points of interconnection with other sources shall be marked at an accessible location at the disconnecting means as a power source and with the rated ac output current and the nominal operating voltage. – NEC 690.54 10) Photovoltaic Power Systems Employing Energy Storage. Photovoltaic power systems employing energy storage shall also be marked with the maximum operating voltage, including any equalization voltage and the polarity of the grounded circuit conductor. – NEC 690.55 11) Identification of Power Sources – NEC 690.56 i) Facilities with Stand-Alone Systems – NEC 690.56(A). Any structure or building with a photovoltaic power system that is not connected to a utility service source and is a stand-alone systems shall have a permanent plaque or directory installed on the exterior of the building or structure at a readily visible location of the building or structure at a readily visible location acceptable to the authority having jurisdiction. The plaque or directory shall indicate the location of system disconnecting means and that the structure contains a stand-alone electrical power system. ii) Facilities with Utility Services and PV Systems – NEC 690.56(B). Buildings or structures with both utility service and a photovoltaic system shall have a permanent plaque or directory providing the location of the service disconnecting means and the photovoltaic system disconnecting means if not located at the same location. 12) Inverter Output Connection – NEC 690.64(7) WARNING INVERTER OUTPUT CONNECTION DO NOT RELOCATE THIS OVERCURRENT DEVICE C) Backfed Circuit Breakers 1) Suitable for backfeed. Circuit breakers, if backfed, shall be suitable for such operation. – NEC 690-64(B)(5) D) Equipment Locations 1) The location of all PV equipment shall be located in plan view, any roof mounted equipment shall be indicated as such. E) Equipment Specification Sheets 1) Provide all PV equipment specification sheets for verification of calculations. Brandon Pearsall Electrical Engineer, PE brandon.pearsall@hawaiicounty.gov Issued by: David Yamamoto, Building Division Chief County of Hawai`i is an Equal Opportunity Provider and Employer.