ABSTRACT
USE-2 wire and Photovoltaic (PV) wire are the two most common wiring methods for connecting PV modules to each other and to connecting PV modules to anything else. These wiring methods are commonly installed under PV modules and do get exposed to sunlight. Wire with not enough strands will strain-harden and break. PV wire may be better than USE-2 wire and has been tested with more UV light, but USE-2 wire may be less expensive. When the PV industry was originally trying to get the code making panel to accept "ungrounded" inverters, they used similar wiring methods as systems with double insulation in Europe. PV wire is often the wire of choice of PV module manufacturers, since it is acceptable everywhere in the world and with every version of the National Electric Code. Solidly grounded systems in the 2017 NEC are rare systems that are not fuse grounded.
