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:i:UNIRAC Unirac Code-Compliant InstaUation Manual SolarMount <br />Step 4: Select Rail Type <br />Selecting a span and rail type affects the price of your <br />installation. Longer spans produce fewer wall or roof <br />penetrations. However, longer spans create higher point load <br />forces on the building structure. A point load force is the <br />amount of force transferred to the building structure at each <br />connection. <br />It is the installer's responsibilitv to verifv that the buildinE <br />structure is strong enousrh to supnort the point load <br />forge <br />Table 10. Downforce Point Load Calculation <br />Total Design Load (downforce) (max of case 1,2or 3): P <br />Module length perpendicular to rails: B <br />Rail Span:L <br />Downforce Point Load: R <br />Step 5: Determine the Downforce Point Load, R (lbs), <br />at each connection based on rail span <br />When designing the Unirac Flush Mount Installation, you <br />must consider the downforce Point Load, R Obs) on the roof <br />structure. <br />The Downforce, Point Load, R (lbs), is determined by <br />multiplying the Total Design Load, P (psf) (Step 1) by the Rail <br />Span, L OU (Step 3) and the Module Length Perpendicular to <br />the Rails, B (#) divided by two. <br />R (lbs) = PLB/2 <br />R = Point Load Obs) <br />P = Total Design Load (psf) <br />L =Rail Span Ut) <br />B = Module Length Perpendicular to Rails (ft) <br />It is the installer's responsibility to verify that the building <br />structure is strong enough to support the maximum point <br />loads calculated according to Step 5. <br />psf Step I <br />x ft <br />x ft Step 4 <br />11 <br />lbs <br />0 <br />Page <br />12