Dated December 1996
Photovoltaic Power Systems and the National Electrical Code: Suggested Practices
John Wiles Southwest Technology Development Institute New Mexico State University 1505 Payne Street Las Cruces, NM 88003
ABSTRACT This suggested practices manual examines the requirements of the NationalElectrical Code (NEC) as they apply to photovoltaic (PV) power systems. The design requirements for the balance of systems components in a PV system are addressed, including conductor selection and sizing, overcurrent protection ratings and location, and disconnect ratings and location. PV array, battery, charge controller, and inverter sizing and selection are not covered, as these items are theresponsibility of the system designer, and they in turn determine the items in this manual. Stand-alone, hybrid, and utility-interactive PV systems are all covered. References are made to applicable sections of the NEC.
National Electrical Code® and NEC ® are registered trademarks of the National Fire Protection Association, Inc., Quincy, Massachusetts 02269
PHOTOVOLTAIC POWER SYSTEMS and theNATIONAL ELECTRICAL CODE
ACKNOWLEDGMENTS Numerous persons throughout the photovoltaic industry reviewed the drafts of this manual and provided comments which are incorporated in this version. Particular thanks go to Joel Davidson, Mike McGoey and Tim Ball, George Peroni, Bob Nicholson, Mark Ralph and Ward Bower, Steve Willey, Tom Lundtveit, and all those who provided useful information at seminars onthe subject. Appendix E is dedicated to John Stevens and Mike Thomas at Sandia National Laboratories. Document editing and layout by Ronald Donaghe, Southwest Technology Development Institute. TECHNICAL COMMENTS TO: John C. Wiles Southwest Technology Development Institute New Mexico State University P.O. Box 30001/Dept. 3 SOLAR 1505 Payne Street Las Cruces, New Mexico 88003-0001 Request forcopies to Photovoltaic Systems Assistance Center at Sandia National Laboratories 505-844-4383 PURPOSE This document is intended to contribute to the wide-spread installation of safe, reliable PV systems that meet the requirements of the National Electrical Code. DISCLAIMER This guide provides information on how the National Electrical Code (NEC) applies to photovoltaic systems. The guide is notintended to supplant or replace the NEC; it paraphrases the NEC where it pertains to photovoltaic systems and should be used with the full text of the NEC. Users of this guide should be thoroughly familiar with the NEC and know the engineering principles and hazards associated with electrical and photovoltaic power systems. The information in this guide is the best available at the time of publicationand is believed to be technically accurate. Application of this information and results obtained are the responsibility of the user. In most locations, all electrical wiring including photovoltaic power systems must be accomplished by a licensed electrician and then inspected by a designated local authority. Some municipalities have additional codes that supplement or replace the NEC. The localinspector has the final say on what is acceptable. In some areas, compliance with codes is not required.
NATIONAL FIRE PROTECTION ASSOCIATION (NFPA) STATEMENT The National Electrical Code including the 1999 National Electrical Code is published and updated every three years by the National Fire Protection Association (NFPA), Batterymarch Park, Quincy, Massachusetts 02269. The National ElectricalCode and the term NEC are registered trademarks of the National Fire Protection Association and may not be used without their permission. Copies of the current edition of the National Electrical Code are available from the NFPA at the above address, most electrical supply distributors, and many bookstores. In most locations, all electrical wiring including photovoltaic power systems must be...