How to Install Solar Panels on Flat Commercial Roof

Preparation

• 1

  Involve a licensed roofing contractor to assess the remaining life of the roof covering. Inspect the site area for the installation to ensure the surface does not require repairs.

• 2

  Investigate moisture problems or leaks and perform repairs as necessary. Some specifications call for the roof to provide a minimum of 20 years of useful life or replacement of existing roof coverings. This approach avoids the expense of removing PV equipment to make roof repairs.

• 3

  Move the photovoltaic installation materials to the roof. Place containers of PV components over joists. Place pallets on a plywood deck to protect the roof surface. Transport materials and equipment on moving equipment with pneumatic tires. Avoid placing the corner of hard panels on the roof surface, which creates point loads in the coverings.

Installing PV Panels

• 4

  Determine the module orientation -- profile or landscape mode. Position the panel so that the short sides run parallel to the rails for profile mode. The panels will have an east-west direction. Attach panels so that the long side of the panel sits parallel to the rail in a north-south direction for landscape mode.

• 5

  Use a stud finder to locate the roof rafters. Lay out the locations of the rail footings. Depending on the system, the distance between footings may vary from 4 to 12 feet. Minimizing the number of footings reduces the risk of developing a roof leak.

• 6

  Drill holes for the lag screws in the center of the rafters. This prevents splitting the wood when inserting the screws for the footings. Attach the footings directly into the roof rafters using the lag screws.

• 7

  Apply roofing sealant around the penetration made in the roof. This ensures a watertight seal, which keeps moisture out of the roofing system and the building. Generally, rail systems require two rails for each row of solar panels. Use panel clamps to secure solar panels to the rails.

• 8

  Refer to the solar arrays wiring diagram to connect the solar panels properly. Use the "series" or "parallel" wiring technique. Some projects require a combination of the two techniques. The series method combines the voltage of the panels. Connect the positive wire of one panel to the negative wire of the nest module. For the parallel method, connect the positive wire of one panel to the negative wire of the adjacent panel. This method adds together the amperage of the solar panels.

• 9

  Connect the solar array wires to a combiner box. The combiner box provides circuit breaker protection for circuits, which prevent overcharge to the system. Link the system to the DC/AC inverter. This device converts direct current electricity to alternating current electricity. Connect the system to the utility meter and then to the building's main electrical panel.