The methods for wiring PV systems are relatively well-defined in theÂ National Electrical Code (NEC)â€”acceptable methods are covered in Part IV in Article 690. This â€œCode Cornerâ€ covers the first section of Part IV, 690.31, â€œWiring Systems.â€
This section first states that all wiring systems recognized by theÂ NEC, both PV-specific and wiring in general, are acceptable for use with PV installations. This is both helpful and a minor burden for installers. Installers are not limited to the methods set in Article 690â€”but the burden is in digging into otherÂ CodeÂ sections to find the proper requirements. Fortunately, only a few wiring methods are typically used in PV systems, which limits the amount ofÂ Code-searching.
The second paragraph in 690.31(A) references PV conductors operating above 30 V and in readily accessible locations. TheÂ CodeÂ requires that PV source and output â€œcircuit conductors shall be guarded or installed in a raceway.â€ The most common scenario where this applies is in ground-mounted arrays when using standard racks. Solutions include installing a fence or other barrier to eliminate the ready access or elevating the conductors at least 8 feet above grade. Confer with your authority having jurisdiction (AHJ) on their interpretation of that definition. Rack manufacturers have been slow to provide a solution; however, at least one product is available (see solarscrim.com). Installing conductors in a raceway is generally not possible, since module junction boxes come with pre-attached module leads and no conduit knockouts.
The next subsections describe the grouping of PV system conductors. The conductors need proper identification at terminations and to be grouped together when they are routed through boxes and raceways. A significant change in this section refers to PV source and output circuits that are routed with non-PV system conductors. (This was covered in 690.4(B) of the 2011Â NECÂ and was moved to 690.31(B) for 2014.) The 2011Â NECÂ required a partition for separating non-PV from PV DC conductors sharing the same raceway, cable tray, or junction box, etc. However, a DC circuit could share the same raceway as an AC inverter output circuit since they were both circuits related to the PV system. In 2014, inverter output circuits were included in the list of circuits that require separation from DC source circuits. Both circuits can be run in a raceway, such as a gutter, as long as a partition is included to separate the circuits. Both AC and DC can be run in the same raceway, provided the two circuits are physically separated.
A common method for establishing this separation is a plastic partition that is mounted to the back of a box or gutter. These are available in various dimensions to match the box you are installing. Once they are attached to the back of the box, they create multiple wiring sections that are separated from each other. These partitions can be sourced from companies such as B-Line or Panduit.