A structural rail connector, commonly called a splice, turns two rails into one. Structural splices have very few limitations, and often two rails connected using a structural rail connector can be treated as a single rail from a loading standpoint. Non-structural splices on the other hand have many limitations. For example, two fourteen-foot rails connected with a non-structural splice must follow the rules of two single rails with one cantilever on each end of each rail. The distance beyond the last attachment on either end of the rail cannot exceed the typical cantilever limitations. This is usually one third of the spacing between attachments used in the rail run. For example, a six-foot span would have a maximum cantilever of two feet on either end of the rail. This includes the distance from the splice on both rails in that rail run.
A cantilever is the allowable distance past the last attachment in which modules will be mounted on the rail. Typically, the allowable cantilever length is equal to one third of the maximum allowable span for the rail. This rule must be considered for non-structural rail connectors. Each racking manufacturer specifies their own rules for rail connectors or splice locations. However, there is very little variation of these rules for mounting manufacturers in the United States.
Rule 1: Rails must be supported by a minimum of two attachments.
Rule 2: The allowable distance between those attachments is determined by many factors:
Rule 3: When working with non-structural splices, a solar panel may never be mounted across a splice that is not supported by two attachments. For example, if your rail is slightly too short to mount your last module, you must install an additional attachment if you will extend the rail using a splice. Using Everest’s Structural Rail Connector eliminates this requirement as long as the cantilever does not exceed more than one third of the span being used. According to Shawn Kelley, at Moment Engineering + Design, “Installing a non-structural splice in a location that it is not advised can lead to potential failure of the rail system or it’s attachments as the rail system becomes segmented (not continuous) at the splice location.”
If the cantilever rules of a non-structural splice are not followed, there will be an excessive amount of deflection in the rail at the location of the non-structural splice. This could result in extreme loads being placed on the clamps and rail attachments in that area for which those components were not designed or tested for. As a reminder, the failure of one of the module clamps or rail attachments can likely result in a catastrophic failure of an entire solar array. This can also cause damage to buildings and personal injuries. Additionally, failure to follow the manufacturers’ guidelines on non-structural splice installations will result in a system installation that voids the manufacturer’s warranty. This leaves the contractor, as a designer and installer, liable for any damages incurred. In the event of a failure of the PV mounting hardware and a warranty claim, the manufacturer will always perform an investigation to confirm if the installer followed the correct installation process according to the assembly guide. If it is determined the system did not follow the manufacturer’s specified rules, a warranty claim will be rejected. Furthermore, any third-party insurance protection may be voided due to failure to comply with the design guide. This will result in costly repairs and potential legal ramifications.
Brian Christie, of Alder Energy in South Carolina, stated:
“The Structural splice allows for more flexibility of unforeseen changes on the fly with the install. In those times when we had a few rails cantilevered too far on one side after all the optimizer mounts, the rail and the clamps were already installed. We did not have to backtrack the install to loosen everything up and move it over. We just cut the end of the rail off that was cantilevered too far on the one side and added it to the side that was short with a splice. With other rail systems, we never considered this option because we would have had to add more flashings because they were not structural.”
Shawn Kelley, of Moment Engineering + Design, explains:
“A structural splice maintains continuity of the rail system and ensures that adequate strength is provided throughout the length of the array.”
Overall, K2’s Structural Rail Connector can improve the installation process, save your company time and money, and reduce waste. A structural rail connector can also help avoid costly damages and protect your company from liability.
Special thanks to Shawn Kelley at Moment Engineering + Design for providing information on this subject. Shawn has been working with K2/Everest for many years to provide the required documentation and expertise for many of K2’s product offerings. If you have any specialty projects or questions, please feel free to contact Moment Engineering + Design at email@example.com or K2 at firstname.lastname@example.org.
K2 Systems offers a truly structural rail connector for CrossRail 44-X and CrossRail 48-X/48-XL.
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