The solar industry, while relatively new, has been growing at an immensely rapid rate, due to the encouragement of its advancement brought on by the establishment and extension of the Solar Investment Tax Credit (ITC), a tax credit equal to 40% the cost of a solar array installation, along with other financial incentives from the government. In 2015 alone, there was over 7,000 MW of new solar photovoltaic capacity installed, and over 200,000 people were employed in the United States solar industry. Due to its fast progression, there have been continuous advancements made to PV technology and procedures.
Article 690 of NFPA 70-2017 reflects this, as it contains many changes for the installation of photovoltaic systems. The earliest significant changes to this section are in Part II Circuit Requirements. This specifies the maximum voltage of two PV system DC circuits under the following environments: “PV system dc circuits on or in one- and two-family dwellings shall be permitted to have a maximum voltage of 600 volts or less”, and “PV system dc circuits on or in other types of buildings shall be permitted to have a maximum voltage of 1000 volts or less.” Additional changes are for the maximum voltage for photovoltaic source and output circuits, DC-to-DC converter source and output circuits, single DC-to-DC converter, two or more series connected DC-to-DC converters, bipolar source and output currents.
Part II also now addresses overcurrent protection, along with arc-fault circuit protection, as in “photovoltaic systems operating at 80 volts dc or greater between an two conductors shall be protected by a listed PV arc-fault circuit interrupter.”
In Part III Disconnecting Means, the standard states that each PV system should consist of no more than 6 switches or sets of circuit breakers, but an alteration to the document notes that single PV system disconnecting means can be permitted for the combined AC output of one or more inverters or ac modules in an interactive system. Furthermore, NFPA 70-2017 bears changes made to the ratings of the PV system disconnecting means, and states: “where the maximum circuit current is greater than 30 amperes for the output circuit of a dc combiner or the input circuit of a charge controller or inverter, an equipment disconnecting means shall be provided for isolation.”
Part III also contains adjustments to the marking of the disconnecting means. The NEC states that each PV system disconnecting means should plainly indicate whether it is in the open (off) or closed (on) position and be permanently marked “PV SYSTEM DISCONNECT”. The device should also be marked with the following:
Part IV Wiring Methods contains changes made for the identification of PV system circuit conductors, stating that the means of identification should be completed by separate color coding, marking tape, tagging, or other approved means.
The changes in Part V Grounding and Bonding are numerous, with many clauses in the section of the NFPA 70-2017 being completely different in the new edition of the National Electrical Code. For grounding configurations, two options have been added: 2-wire PV arrays with one functional grounded conductor and bipolar PV arrays according to 690.7(C) with a functional ground reference (center tap). This section also marks changes to the clauses for ground-fault detection, isolating faulting currents, point of system grounding connection, equipment grounding and bonding, photovoltaic module mounting systems and devices, and equipment secured to grounded metal supports.
Part VI Marking contains far fewer changes, with the most notable alteration made for photovoltaic systems connected to energy source systems, specifying that “the PV system output circuit conductors shall be marked to indicate the polarity where connected to energy storage systems.”
Part VII Connection to Other Sources and Part VIII Energy Storage Systems are virtually entirely different in NFPA 70-2017 than they were in the 2014 edition of the code. These changes call for the PV system to be installed in accordance with the guidelines established by other sections of the standard.
All of these changes, along with any others present to Article 690 of NFPA 70-2017, can be clearly identified by the user, since they are shaded in gray on the document.
NFPA 70-2017 - NFPA 70 National Electrical Code, 2017 edition is available on the ANSI Webstore.
1. National Fire Protection Association (NFPA), NFPA 70-2017: NFPA 70 National Electrical Code, 2017 edition (Quincy: NFPA, 2016), 563.