While large, utility-scale photovoltaic (PV) power systems account for more of the installed megawatts and gigawatts of PV power in the United States, the typical inspector will be inspecting far more residential and small commercial PV systems than utility-scale PV systems. And, while failures in those utility-scale PV systems can be spectacular, these systems are usually ground mounted in remote areas, and damage is restricted to the equipment itself, and of course the pocketbooks of organizations involved directly with the system.

On the other hand, when residential and small commercial PV systems fail, the resulting damage can affect homes, commercial buildings, and people (including first responders) in a very real manner. To ensure the safety of the public, the inspection community including administrative personnel and managers, as well as the people who are responsible for funding must work together to provide an exceptional final PV inspection before the system is turned on. That final inspection, to a great extent, will ensure the safety of an electrical power system that may be generating energy for the next 40 or 50 years, possibly without any further attention.

Facts of Life

More Dangerous. PV systems are potentially more dangerous than the typical residential or commercial electrical power system. With voltages up to 600 V direct current (DC) on residential installations and up to a 1000 volts DC on commercial installations, the voltages are higher than those of normal electrical systems. And, if energy storage systems are involved, the currents may also be higher than those found on non-PV systems. Energy storage systems may be operating at voltages up to 600 volts DC in residences.

More Complexity. PV systems are more complex than the typical residential or commercial electrical power system and that complexity is continually increasing due to technology changes and changing code requirements. We now have frequently changing requirements for the PV Rapid Shutdown Systems (PVRSS) to protect first responders (690.12). We have DC PV Arc Fault Circuit Interrupter (DCPVAFCI) requirements (690.11). And we have PV utility-interactive inverters with changing requirements and designs due to the new utility requirements in some states to provide PV “ride through” of utility disturbances including low voltage (down to 50% of nominal) and frequency variations.

Installer Qualifications. While many PV systems are being installed by competent individuals and organizations, there are still numerous systems being installed with people who have less than full competency in the required knowledge base and required skills (photo 1). Homeowners can install PV systems in some jurisdictions with no permits or inspections other than what the utility might potentially require. Unqualified electricians, who have had no specific PV training are installing PV systems. And, new “PV installation companies” are popping up right and left to take advantage of the boom in PV installations without being fully trained to do so properly. As an aside, today as I write this, I received a call from an electrician who had been hired to install a PV system for a residential customer who had bought the equipment himself. The electrician had absolutely no knowledge of how to do the job or that there were any requirements in the National Electrical Code (NEC) for such installations. It also appears that the customer may have purchased an unlisted inverter on the Internet where all things are available.

Photo 1. Some PV systems may experience trouble when installed by less than competent organizations.
Photo 1. Some PV systems may experience trouble when installed by less than competent organizations.

AHJ Qualifications. As uncomfortable as it might be, we must admit that our authorities having jurisdiction (AHJs) and local inspection requirements are not always up to the task of ensuring that the installed PV system is safe and will operate safely for many years to come.

The Electrical Specialist. There are AHJs in the inspection community that have come up through the ranks as master electricians with additional training in PV systems and who have been dealing with PV systems daily since the beginning—sometimes as early as the mid-1980s. These people are the electrical specialist inspectors. These individuals are frequently involved in PV more than just at the inspection level. They may be members of Code Making Panels for the NEC, members of the Underwriters Laboratories(UL) Standards Technical Panels for PV equipment, active members in local IAEI chapters and IAEI sections; and, finally, they may even be writing articles in the IAEI magazine.

The Newly Minted Combination Inspector. At the other end of the spectrum, we have the newly hired combination inspector who may have come from the plumbing industry who is now inspecting not only plumbing systems but also electrical power systems, including PV systems. This individual will not usually have a firm background in the NEC, nor will he or she be familiar with the requirements for a quality electrical power system, let alone the very specific safety requirements associated with PV systems.

The Permitting and Inspection Process. The process for permitting and inspecting PV systems varies substantially throughout the country. In some areas of the country, no inspections are conducted on PV systems. In other areas, a permit is nothing more than a form filled out with the location of the electrical system, and a fee is paid. In some states, there are no inspections of residential PV systems, and the utility is responsible for the quality of that installation before allowing the interconnection.

On the other hand, many jurisdictions wisely require a full permitting package with diagrams, a plan review stage, and a detailed inspection before approving the system as complying with the NEC. Then the utility performs their required inspections prior to interconnection; and after the system has been powered up, there may be a final inspection by the AHJ.

Budget and Administrative Restrictions. In many areas of the country, funding is tight for the inspection organizations. Combination inspectors are being hired more frequently than specialist electrical inspectors. Budgetary and manpower restrictions are forcing inspectors to do more inspections per day and, in some cases, allowing only 15 minutes for an inspection. A thorough inspection of a PV system might require two hours or more, including the plan review. In many areas, this amount of time is just not available to the inspector.

Training is also an issue for AHJs who inspect PV systems. Funding is frequently not available, nor is time allocated for the proper training of inspectors who will be dealing with the constantly changing requirements in the code for PV systems. To ensure the safety of the public, the inspector should be at least as familiar with PV systems as the PV installer and PV systems designer. This familiarity requires periodic and continuing training for the inspectors (photo 2).

Photo 2. Hands-on field inspection training for AHJs
Photo 2. Hands-on field inspection training for AHJs

It should be noted that PV systems and PV equipment are becoming complex to the extent that the instructions for installing such systems can no longer be fully included in the NEC. The instructions for installation of that equipment will be found only in the manuals for the listed equipment; and those instructions are, to say the least, quite complex; far more complex than can be put in the NEC [110.3(B)].

Moreover, for unknown reasons, some jurisdictions have insurance policies that prohibit the AHJ from going onto the roof to inspect not only PV systems but also HVAC equipment. This prohibition is particularly troublesome where many commercial PV systems are mounted on the roofs of buildings, and 90% of the PV equipment that should be inspected is on the roof. Here in the Southwest, with our flat-roofed and low-sloped roof buildings, PV systems and sometimes the inverter are also frequently mounted on the roof. Of course, with the AC PV module system, nearly all the system that should be inspected is found on the roof.

The Way It Should Be Done—My Opinion

The Overall Process. The inspection process for a PV system should begin with the permitting process that should include a full-system description which shows a three-line diagram and manuals for all PV-unique equipment being installed. Hopefully, permits will be issued only to individuals or organizations who are qualified to install PV systems and have the necessary licenses. In the best of circumstances, the permit applicant will be well-versed in installing residential and commercial electrical systems, with additional training in PV code requirements and installations.

A plan review step in the comfortable confines of an office environment should be performed on the permit application material. Unfortunately, many aspects of the PV installation cannot be verified after the system is installed. Modules will be mounted close to a roof, and the labels cannot be seen. Conductors may be installed in not readily accessible areas, and sizing and types will be difficult to verify.

The initial inspection should verify that all requirements in the NEC have been met and that the equipment that has been installed agrees with the information provided in the permit application. Typically, there is no utility interface connection at this time, and several parts of the system operation cannot be evaluated for safety.

In most cases, the initial PV inspection will be followed by a utility inspection where ac electrical power is connected to the system by the utility. After this is done, a subsequent inspection should be made to verify that equipment like PV Rapid Shutdown systems and the like are functioning as intended.

The various stages of this process will be examined in more detail in this article and a subsequent one in this “Perspectives on PV” series. Comments and suggestions on the material presented are always welcome.

First Comes Training and Education. It is imperative that the inspector of PV systems to get adequate knowledge and training so that he or she can effectively ensure the safety of the public. Acquiring this background is not as easy as it sounds.

For example, I am involved in conference calls a couple of times a week dealing with the standards associated with PV systems. Also, I  review the new codes and standards on a regular basis and assist in writing the same, and even I have trouble keeping up with the changing technology, the changing standards, and the changing codes associated with PV.

As inspectors, we must take it upon ourselves to get as much training in this ever-changing technology as possible. There are online training programs, and there are hardcopy materials that can be used. The first example that comes to mind of hardcopy material is the National Electrical Code Handbook (NECH). In many cases, the informative material found in the NECH is based upon the background and technical information that went into developing the code requirement. Every inspector should have a copy of the Handbook and review this document almost continually. I have found that it takes nearly three years to gain familiarity with the current version of the Code before the new version is released.

Another hardcopy source is these “Perspectives on PV” articles that are archived on the website below. We should also review the IAEI Publications Catalog (http://www.iaei.org/web/store) for all the significant documents that summarize the new code requirements. These documents are updated every code cycle, and the IAEI Publications Catalog is probably the best source for a broad spectrum of documents that can be used in educating the inspector on the nuances and changes in the code.

Another source of wide-ranging technical articles on PV systems, PV equipment, and PV installations can be found on the Solar America Board of Codes and Standards (solarabcs) website (http://www.solarabcs.org/).

One source of online training that is been widely advertised in IAEI magazine and other publications is the “PV Online Training Course for Code Officials” developed by the Interstate Renewable Energy Council (IREC), IAEI and others. It is free and can be accessed here: www.pvonlinetraining.org. Be advised; a game is included in this training program. See the excellent article in IAEI magazine (Nov-Dec 2016) on this program (http://iaeimagazine.org/magazine/2016/11/04/become-solar-smarter-with-pv-training-online/).

Building Officials and Administrators. Inspectors must be provided with adequate funding and time allowances for the necessary study and training. Workshops and presentations may be brought to a central location so that many inspectors can participate, or video conferencing/webinars can be set up to ensure that all inspectors maintain currency in their respective disciplines, in this case, PV systems.

The Permit

The permit for a PV system should include more than a simple form and the payment of a fee. That permit application should contain the following:

  1. A three-line diagram of the system showing, as a minimum, conductor sizes, conduit sizes, equipment grounding circuits, disconnects, overcurrent protection, and the location and method of making the utility interconnection.
  2. The code calculations for the maximum system voltage including the expected lowest temperature at the site, the ampacity calculations for each circuit including the ambient temperatures used, and the NEC 705.12 calculations for the interconnection point.
  3. A copy of the installation manuals for the PV module, the dc combiner, the inverter, the PV rapid shutdown system/equipment and any other PV unique equipment, as well as, cut sheets for the various disconnects and any load centers.
  4. PV module mounting and grounding details showing that these installation details are compatible and comply with the instructions in the PV module and the mounting rack manuals.

Requiring this material in the permit application will help to ensure that qualified persons are making that application. The material also will be useful in the plan review process (described below) that will facilitate the actual on-site inspection.

Expedited Permitting. For those jurisdictions not having a formal permitting process, an expedited permitting process developed by the Solar American Board of Codes and Standards (SOLARABCS) and written by Bill Brooks can be found here: http://www.solarabcs.org/about/publications/reports/expedited-permit/

This expedited permitting process is very useful for PV systems of 10 kW and less and includes diagrams, fill-in forms, and code-based calculations. It has been used by numerous jurisdictions throughout the country and modified for use with additional systems by other jurisdictions.

The Plan Review

Advantages. One advantage of having the details described above submitted with the permit application is that a quick review of this material will give some indication of the capabilities and competencies of the person making the application and, hopefully, the person installing the system. If the basic system design in the permit package does not meet code requirements, it is almost certain that the system will not be installed in a safe and code-compliant manner. Another advantage of performing a plan review is the fact that the review can verify partial code-compliance in the warm, quiet, office environment and not out in the cold, blustery or hot, sunbaked environment of a rooftop PV system.

As mentioned above, it is physically not possible to fully access all the labels and markings on the PV modules and many of the cables after the PV array has been installed. The PV arrays are, in many cases, mounted within a few inches of the roof and it would require unmounting a PV module to view the data label on the back. Depending on the module grounding method being used, grounding hardware might have to be replaced when a module is removed from the racking system. Conductors installed under the modules and the connectors used between the PV modules and the field-installed wiring may not be easily accessible.

Additionally, reviewing the system on paper allows the AHJ to see the overall system and how the various components are interconnected. It will also show the flow of power through the system which will assist in determining if disconnects and overcurrent protection devices have been located properly.

To a certain extent, some of this information is provided by a full permit package and can be used to verify code compliance. Of course, this assumes that the equipment and materials in the permit package match the equipment and materials that actually will be installed; and that may not always be the case. This item should appear on the field inspection checklist.

Items to Look For. Here is a brief checklist of items that should be verified during a plan check. Significant numbers of items that are not code-compliant may signify that the basic PV system design is inadequate and that the permit package be returned to the submitter for corrections before any field inspection can be undertaken.

  • All equipment listed for the specific application [690.4(B)]
  • Modules and racks compatible for mounting and grounding [110.3(B)]
  • Calculated maximum system voltage less than rated maximum equipment voltage [690.7]
  • Cable types suitable for the environments, suitable for the circuit, and properly rated [690.8]
  • Conduit and raceway selections appropriate for the environments and code- compliant [Chapter 3]
  • Conduit fill calculations correct [Annex C]
  • Disconnects suitable for the type system-grounded or ungrounded
  • Disconnects properly rated and properly located [690 Part III]
  • Overcurrent devices properly rated and properly located [690.9]
  • Utility point of connection properly rated and located [705.12]
  • Any utility-required disconnects and meter properly rated and located
  • Equipment grounding and system grounding circuits correct
  • PV Rapid Shutdown System equipment located in circuits where required by instructions [110.3(B)]
  • DC combiners properly rated
  • Inverter and inverter circuits properly rated for dc inputs and ac output

To Be Continued.  The Inspection Process will continue in the next “Perspectives on PV” with suggestions for the field inspection.


Photovoltaic power systems are not going to go away. As one of the key components dealing with the current and future very real power/energy shortages due to climate change, PV systems are going to be a major player in our nation’s energy mix. They are going to become more complex.

Those of us in the inspection community and those associated with the inspection community, including inspectors at all levels, chief inspectors, building officials, and administrators responsible for funding, need to work diligently to increase the competency and quality of our inspection process and our inspection force.

For More Information

The author has retired from the Southwest Technology Development Institute at New Mexico State University but is devoting about 25% of his time to PV activities in order to keep involved in writing these “Perspectives on PV’ articles in the IAEI News and to stay active in the NEC and UL Standards development process. Seven to eight-hour presentations are still available on PV and the Code, and they cover 2011–2017 NEC requirements. He can be reached at e-mail: jwiles@nmsu.edu;  phone: 575-646-6105

The Southwest Technology Development Institute web site maintains a PV Systems Inspector/Installer Checklist and all copies of the previous “Perspectives on PV” articles for easy downloading. A color copy of the latest version (1.93) of the 150-page, Photovoltaic Power Systems and the 2005 National Electrical Code: Suggested Practices, written by the author, may be downloaded from this website: https://swtdi.nmsu.edu/codes-standards/

John Wiles
John Wiles retired in April 2013 as a Senior Research Engineer at the Southwest Technology Development Institute at New Mexico State University. However, he works part time as 25% employee and continues to assist the PV industry, electrical contractors, electrical inspectors, and purchasing agencies in understanding the PV requirements of the National Electrical Code (NEC). He is an active member on six UL Standards Technical Panels. John served as Secretary for the PV Industry Forum involved with Article 690 of the NEC. Over 30 submissions were accepted for the 2011 NEC and 55 proposals were submitted for the 2014 Code. He drafted the text for Article 690 in the 2005 NEC Handbook and 2008 NEC Handbook. Fieldwork involves balance of systems design for PV systems, inspections and acceptance testing of PV systems, test and evaluation of PV components, and the design and installation of data acquisition systems. He bought his first codebook in 1960 and installed his first PV system in 1984. He lived in an off-grid, PV/wind-powered home (permitted and inspected, of course) with his wife Patti, two dogs, and a cat for more than 16 years. His retirement home currently has a 8.5 kW utility-interactive PV system will full-house battery backup and now has three dogs and two cats. He writes the “Perspectives on PV” series of articles for the International Association of Electrical Inspectors in their IAEI News magazine and has published an IAEI book on PV and the NEC for inspectors and plan reviewers. He has a Master of Science Degree in Electrical Engineering.