Solar Builder

MAY-JUN 2018

Solar Builder focuses on the installation/construction of solar PV systems. We cover the latest PV technology (modules, mounting, inverters, storage, BOS) and equip installers/contractors with tips and tools to make informed purchasing decisions.

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Page 35 of 55

36 M AY / J U N E 2 0 1 8 and secured at the end of each day or whenever inclement or windy weather is predicted. Ensure that the wheel load for rolling equipment does not exceed 15 psi. For example, wheeled equipment capable of carry- ing 1,200 lbs (combined self weight plus load) should have at least 80 sq in. of wheel contact area. If the equipment distributes the load on four wheels evenly, each wheel should have at least 20 sq in. of contact area. If the contact width is 4 in., the contact length must be at least 5 in. If the area is insufficient, either the load must be reduced or additional wheels must be added. For minor inadequacies, small amounts of air may be released f rom the tires to increase the contact areas. Guidelines for permanent protection Rigid conduit supports, metal ballast trays or rigid racking that sits directly on the roof, or other equipment subject to ther- mally driven oscillation movement, will require appropriately sized roof material matching slip sheets. Soft durometer PV racking support pads that are not subject to thermally driven oscillation and have been proven to be compati- ble with the roof membrane system type, may be — with the approval of the roof manufacturer — installed without slip sheets. PV system support pads that have not been proven to be com- patible in direct contact with the roof membrane (or if move- ment of the support pads relative to the roof are expected) will require an appropriately sized roof material matching slip or separator sheets. If the roof is TPO, then the slip sheets are TPO — EPDM for EPDM roofs and PVC for PVC roofs. Slip sheet thickness is typically minimum .060 but material thickness matches above that. For example, .060 slip sheet for a .045 roof, .060 slip sheet for a .060 roof and .090 slip sheet for a .090 roof. The slip sheets can be tack welded, tack adhered or even loose depending on the roof manufacturer. Upon completion of the PV installation, provide permanent walk pads at areas designated by the roof manufacturer as a location requir- ing protection. Typical locations include: a minimum 30-in. x 30-in. walk pad installed at all door or ladder access points and all work station locations on rooftop mounted mechanical equipment. Work station locations pertaining to a PV installation may include rooftop mounted inverters or combiner boxes. Additionally, any PV equip- ment that requires more than monthly service should have a dedi- cated path of walkway pads from the roof access point to the service- dependent equipment. The walk pad system should consist of the roof manufacturer's roof-compatible walk pad installed utilizing the roof manufacturer's recommended method of securement. Peter Corsi is a consultant for N.B.S. Consultants. Place all pallet loads on foam board sheets or similar materials that can spread the load without damaging the membrane or insulation below.

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