On day 3, the electricians mounted a large exterior sub panel with main disconnect on the back porch near the electric meter. This was a better solution than the one I had originally planned and submitted to the electric utility for approval--the larger box allowed for additional PV circuits if we decided to expand in the future to support an electric car or hybrid car.
Installing the subpanel
The electricians also ran 12-gauge Romex for the two PV circuits into the attic through a short length of PVC conduit on the roof. James, the master electricianexplained to me that the electrical code permits the use of Romex this way as long as the run on the roof in the conduit is two feet or less and the outer sheathing is stripped from the wires to improve cooling. James and Steve planned the roof penetration point for the conduit so that it was mostly hidden from ground view under the yet-to-be-installed PV modules. This should also ensure weather resistance and longevity for the conduit, the joints, and the roof penetration. We used 1" conduit to ensure ample room for the wires to stay cool and to allow for the possibility of additional PV circuits later.
The PVC conduit and junction box will be mostly hidden by the last PV module.
The junction box transitions from the special cable supplied with the
enphase microinverters to regular Romex wire,
the outer sheathing stripped from the Romex for cooling purposes.
Next,we we installed the remaining two PV modules, and ensured that all of the modules were fastened to the rails with 10 foot-pounds of torque as per the manufacturer specifications.
At the end of Day 3, the 3.8 kilowatt array was completely installed and wired through the attic
to a subpanel on the back porch wall around the corner from the electric meter.
The next steps were to attach the AC disconnect, and wire the system into the house's main electric panel in the basement. We also had to attached two signs required by the electric utility, and to schedule an inspection by the utility's engineer. If approved, the next step would be for the electric utility to install the reversible electric meter in place of the existing electric meter, and connect the array to the grid.