String Configuration: This site has some evergreen trees to the East that cause some shading on this side of the array in the winter mornings. They divided the array into 4 strings that split the upper two rows of modules in half east:west. „It’s more work wiring but prevents this AM shading from taking down the output of the multiple strings,“ said Blake. „The problem is that the array will make a lot less energy over its service life, so its important to spend the time for a high quality install. “No Combining: Both the POS and NEG conductor of each of the 4 strings (8 conductors plus ground) are brought through a switched pass through box on the roof and brought through conduit (larger diameter to hold all the wires) to the basement into a breakout box. Although more expensive, this allows for future string-level troubleshooting from the ground which is really nice during snowy-cold New Hampshire winters, saving the homeowner money in the long-run. Breakout box near inverter and wiring trough: We pass the 4 separate strings (and ground) through a fused breakout box and then into a trough below the inverters in order to stay organized. Multiple MPPT channels: We use multiple inverters with multiple MPPT channels in order to maximize the electrical output of each string. This is why we always choose Fronius. It is considerably more expensive to build a system this way but it makes for a vastly superior system in terms of service life energy production for our customers.
„There is also a huge potential reliability benefit in building a PV system this way as compared to building with module level electronics,“ said Blake. „There is a much better chance that string inverters sitting in a cool-dry basement will outlast any module level electronics out in the weather subject to temperature (and wide humidity) variations of 130 degrees F (-30F to 100F) as in New Hampshire!“