A 95 kW commercial rooftop PV case study — ballasted racking under a real structural load check, three-phase string inverter selection, an NEC 705 load-side interconnection that fails the 120% busbar rule, and the supply-side tap that resolves it.
The project brief: a Phoenix, Arizona big-box retail store with a flat membrane roof and a fully-utilized 800A electrical service wants commercial rooftop solar. Framed as this program's mid-scale integration project, it layers ballasted racking under a structural load check, three-phase inverter selection, and a real NEC 705 interconnection decision on top of the residential baseline in project 1.
This module walks the whole design the way a real commercial PV designer would: an east-west ballasted racking layout checked against the roof's actual allowable dead load, a 1000V string-sizing calculation for a non-dwelling system, the 120% busbar rule worked against this building's real 800A panel — where it fails — and the supply-side tap that NEC 705.12(A) allows instead, plus a financial analysis with the federal ITC applied. The full worked numbers, complete bill of materials, and finished design reasoning are part of the unlocked module below.