Pv Alexsl I Stock Getty Images Plus 5df7f1a5daac1

National Electrical Code

Photovoltaic Systems — Part 2

Dec. 16, 2019

The ins and outs of electrical requirements for PV installations from Art. 690.

The circuit requirement for photovoltaic (PV) systems are covered in Part II of the 2017 National Electrical Code (NEC). To correctly size the overcurrent protection [Sec. 690.9] and conductors, you must first determine the maximum voltage [Sec. 690.7] and the maximum current [Sec. 690.8].

The maximum voltage of any PC system is the highest voltage between any two circuit conductors or any circuit conductor and ground [Sec. 690.7]. While this sounds straightforward enough, there's a three-step calculation process for the PV source and output circuits. But if you have a single DC-to-DC converter the maximum rated voltage of the system is the maximum rated voltage of that converter. If you have more than one converter (series connected), instructions for calculating the maximum rated voltage come with the converters.

You can calculate the maximum current by one of two methods:

Sum up all the parallel-connected PV module-rated short circuit currents, then multiply by 125%.
For systems that can generate 100kW or more, you can base it on the highest 3-hour current average resulting from the simulated local irradiance, accounting for elevation and orientation. This requires a PE stamp.

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.