Safety requirements for wiring systems and connectors for photovoltaic systems

Safety requirements for roof-mounted photovoltaic (PV) arrays were established by considering the environmental use-conditions applicable to PV arrays and the differences between integral-, direct-, standoff- and rack-mounted modules. Those articles in the National Electrical Code (NEC) covering wiring systems are discussed to: (1) define the wiring systems; (2) identify the permitted uses and use-restrictions; (3) outline the advantages and disadvantages; and (4) address the concerns regarding support, protection against mechanical damage, and wet versus dry locations. The advantages and disadvantages of each wiring system are assessed to arrive at candidate wiring systems that are best suited for use in PV arrays. For candidate wiring systems having prohibitive use-restrictions issues are considered that need to be addressed by any proposed revision to the National Electrical Code to permit acceptance by the inspection authorities. Various wiring termination methods permitted by the NEC are discussed and those which have features that are desirable for PV applications are identified. Performance and construction requirements for PV cable and for PV connectors are presented in separate outlines of proposed investigations of these products.