Charlie:
The answer depends on whether the "system" (modules and micro-inverters) is "grounded" or "ungrounded". I think you are describing a "grounded" system, but it's not totally clear based on your issue description. If the micro-inverter is "transformer-less" the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC. I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters. Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be "floating" or "ungrounded". If the system is "ungrounded", a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV-), then your PV system is considered to be "grounded". If the system is "grounded", the combined DC-GEC and AC-EGC sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table 250.122) and GEC [250.166(B)] sizes will be required. More specifics on the PV module Vmpp and micro-inverter you're dealing with would be helpful. Regards, Gary Willett Icarus Solar On 9/17/13 8:37 PM, Aladdin Solar wrote:
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