This article originally appeared in SolarPro Magazine in Issue 8.3. | by Ryan Mayfield, Paul Gibbs and Paul Grana
“Ask almost anyone who works for a system integrator how to size PV system conductors with respect to voltage drop, and the nearly unanimous answer is “Keep voltage drop to less than 2%.” Typically, PV system designers hold a maximum 2% standard on both the dc and ac sides of the inverter. When pushed to explain why, nearly everyone (ourselves included) answers with some form of “That’s how it’s always been done.” As the industry continues to reduce system costs, however, we must reassess this rule of thumb to see if it still applies.”
In this SolarPro article, Mayfield, Gibbs and Grana dig deep into the voltage drop on the dc side of the inverter to see if the 2% threshold is still ideal and rigorously analyze the effects of changing system costs and design techniques. They use production modeling and financial analysis tools to quantify and monetize the actual voltage drop and wire loss values to draw some realistic conclusions regarding optimal conductor sizing.
Learn with Ryan Mayfield, Solar PV Technical Editor at SolarPro, by enrolling in his 10-week technical course, Megawatt Design. Ryan covers all types of large solar PV systems, including commercial rooftop systems. As a course capstone project, students will submit drawings and equipment selection for a real megawatt scale project using real inputs. Enroll today and earn 30 NABCEP Advanced Credit Hours, 6 NABCEP Technical/JTA, 6 NABCEP Elective, 3 NABCEP NEC and 30 AIA LU/HSW Credits… tools and templates included.
About author Ryan Mayfield – President, Renewable Energy Associates
Ryan Mayfield has been working in the renewable energy field since 1999 and is the President of Renewable Energy Associates, a consulting firm providing design, support and educational services for electrical contractors, architectural and engineering firms, manufacturers and government agencies. Ryan serves as Photovoltaic Systems Technical Editor for SolarPro Magazine, regularly writing feature articles in SolarPro and Home Power magazines, and wrote PV Design and Installation for Dummies. Ryan was also a contributor and video team member for Mike Holt’s Understanding the NEC Requirements for Solar Photovoltaic Systems. Ryan teaches various PV courses across the nation for electricians, existing solar professionals, code officials, inspectors and individuals looking to join the solar industry. Class topics include National Electrical Code and PV systems, residential and commercial PV systems. Ryan holds a Limited Renewable Energy Technician (LRT) license in Oregon, is an Oregon Solar Energy Industries Association (OSEIA) board member and chairs the state’s LRT apprenticeship committee.
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