At this site, the intermodule wiring is zip-tied to the rails but the string homeruns are laying loose on the roof, which is poor workmanship. Over time the rough shingles will wear away on the insulation compromising its integrity and putting the system at risk for faults. In the winter, snow and ice will surround this wiring, and as the frozen ice tries to slide down the roof it will pull on the conductors. Wire must be kept up off the roof and secured to the rails.
