This page documents the construction of an 8kW photovoltaic array comprising 32 Siliken SLK60P6L 250W panels with Enphase M215 micro-inverters.


The first step was the construction of the Unirac U-LA frame, made from 2" Schedule 40 galvanized steel pipe and Unirac's aluminum and stainless steel components. The pipe was set in concrete in 12" diameter holes 36" deep.


After the concrete cured, Enphase M215 micro-inverters were attached to the rails and the rails were mounted on the horizontal pipes. The panels were then mounted on the rails.


The next phase of the project was the burial and installation of the electrical lines connecting the arrays to the residential electrical service. Junction boxes were mounted on each array with Superstrut, and EMT conduit was used to bring 4awg aluminum URD cable from these boxes underground to a depth of 24 inches. The cables were directly buried in trenches running to a nearby power pole where EMT conduit was used to carry them from the ground into a load center mounted on the pole.


A line diagram of the system:

This next series of photos shows the excavation and burial of the electrical lines.


After the trenches were filled and the rocks brought to the surface by the excavation were moved into a series of rock walls, it was time to install and interconnect a number of electrical components and to mount signs where required by the NEC.


The junction boxes were provided with lockable switches and pilot lights.


The load center was fitted with a Square D SDSA1175 type 1 surge suppressor and a 100A main breaker.


After the state electrical inspector's approval, the service entrance received a new meter provisioned to provide net metering.


A transfer switch was installed to provide the required utility disconnect. It's currently necessary to include a 'visible blade disconnect switch' but the utility has indicated they will never use it since their preferred disconnect is either the main breaker on the meter box or the meter itself. The large and pointless expense associated with the disconnect was offset in this case by making the disconnect a transfer switch, which may be useful if a generator is eventually installed.

The reasons this Utility External Disconnect Switch ("UEDS") is required are historical. More information regarding the issue is available in the U.S. Department of Energy's Solar America Board for Codes and Standards' report, Utility External Disconnect Switch: Practical, Legal, and Technical Reasons to Eliminate the Requirement, available at http://www.solarabcs.org/about/publications/reports/ued/index.html.


Here are some photos of the completed system:


Enphase provides web-based real-time tracking of their hardware's performance through their Enlighten software system. You can view the current status of this photovoltaic system by visiting https://enlighten.enphaseenergy.com/public/systems/VZ8X127628.


Phone: (307) 322-1519
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