Ever-increasing code complexity makes it easier to fail electrical inspections. Here’s how to make sure your PV system gets the green light.
The first residential PV projects—remote, off-grid systems—were installed far from the long arm of building inspectors. As a consequence, many early PV installers were not familiar with and did not follow the standards set by the National Electrical Code (NEC), the International Building Code (IBC), and local jurisdictions.
But that’s changed. Multitudes of mainstream systems installed on residential roofs have focused attention on safety requirements, often calling for multiple permits and inspections. Installation techniques and practices have evolved accordingly.
Complicating residential PV installation is the introduction of new equipment and methods. To keep up with changing products, governing codes are being updated. This requires contractors to stay abreast of new information and requirements as they are released. Many new—and sometimes old—code compliance issues surface during PV system installation and inspection. Additionally, depending on your jurisdiction, you may be held to current code cycles or previous versions. This can lead to confusion among contractors, PV installers, and enforcement and inspection officials, especially as they communicate with peers in other states and jurisdictions.
The NEC is the guiding document for the electrical portion of PV installations. Some jurisdictions have additional or different requirements, but most are based on the NEC. While the NEC is considered the premier document guiding electrical installations, its acceptance and interpretation is determined by the authority having jurisdiction (AHJ, or electrical inspector), as outlined in Section 90.4.
Sloppy work. NEC Section 110.12 states that “Electrical equipment shall be installed in a neat and workmanlike manner.” While the Code does not have specific guidelines to illustrate this requirement, and inspectors will have a hard time defining it, they will know it when they see it. When work is done poorly, it is a cue to inspectors to look even harder for additional Code violations. The National Electrical Installation Standard—Standard for Good Workmanship in Electrical Contracting published by the National Electrical Contractors Association defines this requirement.
Wire management is one critical issue to consider during installation. Since most PV modules come with factory-installed quick-connect plugs, using conduit to protect and manage the array wiring can be challenging. Plus, wiring must be properly supported to prevent it from damage, especially where it could be exposed to mechanical wear and tear.
Not installed to listing. Section 110.3(B) says that listed or labeled equipment must be used for its intended purpose. A common electrical mistake is to install an overcurrent protection device (OCPD), such as a circuit breaker or fuse that has the incorrect amperage rating, thereby violating the inverter manufacturer’s listing. This can inadequately protect the conductors or result in nuisance tripping, which ultimately reduces energy production.
Improperly sized fuses or circuit breakers for PV source circuits present another issue. All PV modules come with a series fuse rating to determine the maximum PV source circuits’ overcurrent protection. The minimum OCPD used to protect PV power circuits needs to be sized based on NEC Section 690.8—not based on what is on the truck that day.