Laserfiche WebLink
Document #524734 Rev G, Vol. 2 6 SunPower Proprietary <br />Methodology: <br />The maximum allowable spans shown in the tables are based on a combination of dead, wind, seismic, and snow <br />loads calculated from the inputs above and combined using LRFD combinations. The maximum forces are then <br />compared to the minimum capacities determined in the following ways: <br />• Rail bending and shear: ADM1 LRFD checks <br />• Rail to roof attachment: SunPower Test Reports of the rail bolt between the rail and the roof attachment. <br />• Roof attachment: Manufacturer product information <br />• Roof attachment to rafter: Lag screw withdrawal and shear per NDS <br />• The reported maximum spacing is the greatest allowed spacing, rounded down to the nearest rafter <br />spacing increment, for which the demand/capacity ratios are less than or equal to 1.0 , assuming both 16” <br />and 24” rafter spacings. <br />• These tables do not consider the strength of the supporting roof structure. In areas of low snow load, the <br />weight of the array is often considered to offset the design live load of the roof, since personnel and <br />equipment cannot be placed on top of the array. It is recommended to stagger attachment points, as <br />shown in Figure 1, to evenly distribute loads to the rafters. <br />Figure 1 <br />• These tables assume that each module is installed centered over a pair of rails, as shown in Figure 2(a). In <br />cases where one rail is closer to the midpoint of the module, as shown in Figure 2(b), adjustments to the <br />spacing may be required. <br />Figure 2 <br />3428 S <br />Ct08/09/23