CompRail™ PV Mounting Hardware

 An Introduction to the CompRail Concept

Most PV racking systems on the market today utilize dual strut style runners underneath rows of PV modules.  Top-side clips are then used to attach the PV modules to the runners.

The CompRail™ Compressed Rail Mounting System (CRMS) is distinctly different.  CompRail™ utilizes a common lower rail that bridges adjacent rows of modules.  The PV modules rest on shelves that extend from each side of the lower rail.  The modules are then held captive by an upper rail that bolts into the lower rail and compresses the PV modules between the rails.

Because both rails are monolithic and extend the entire length of the row, they form a structurally superior frame that utilizes the continuous PV framewall to increase the rigidity of the entire racking structure.

 Anatomy of the CompRail System

The CompRail™ system has two distinct components: an upper rail and a lower rail that are compressed by a 5/16”-18 stainless steel button head bolt.  Both rails are fabricated from 6063-T6 aluminum alloy and are available in mill finish, clear or bronze anodized material.

The lower mill finish rail contains a captive threaded insert made from cold headed 5056 aluminum.  The inserts for the anodized material are formed from 400 series Monel. The insert is cold formed onto the rail and does not require access when tightening the compression bolt.

A drill starter mark/groove has been placed on the back side of the lower rail to center the attachment point holes used to fasten the lower rails to the strut feet or runners.

The upper rail is a structural hollow that allows the compression force of the bolt to be spread over a large distance of the PV frame.  The upper rail has 3/8” bolt holes placed at 20” O.C. to match the threaded inserts in the lower rail.

 Engineered for Aesthetics, Performance & Cost
CompRail is designed to provide the optimal blend of appearance, mechanical integrity and cost effectiveness.  CompRail achieves an aesthetic “seamless” top-side appearance by utilizing a monolithic rail system.  This same monolithic structure, coupled with a structural hollow upper rail, makes CompRail one of the most rigid mounting racks on the market.  This structural integrity does not come, however, at the expense of added material cost.  CompRail has been designed with the assistance of computer-based finite element analysis to locate more material where the rail will be stressed and remove it from sections where it serves no purpose.  The incorporation of all stainless steel fasteners provides the assurance that CompRail will maintain its strength over the life of the system in even the most adverse environments.  This optimization of design elements makes CompRail attractive, strong, durable and priced to give the competition fits.

 Benefits of the CompRail System

CompRail is based on an entirely different design philosophy than under-module racking systems utilizing Dual Strut Runners (DSR).  Many examples of the DSR style systems are commercially available, including: UniRac, Pro Solar, Two Seas, and Direct Power & Water.  The primary advantages of CompRail over DSR type racking systems are as follows:

  • CompRail provides a shared rail structure that allows a single rail to support each row of modules (plus one for the free end of the array).  This contrasts to DSR systems that require two rails per row.  As an example, if you rack 4 rows of modules with a DSR system you will need 8 separate rails.  An equivalent CompRail system requires only five rails.
  • When CompRail is combined with SunEarth’s exclusive RexRack tilt-rack system, the solar strut support hardware reinforces the lateral rigidity of the array.  Each tilt up row in a DSR system is independent and cannot share lateral loads with adjacent rows.  As a result, DSR racks may require cross bracing at higher rack heights.
  • CompRail can greatly reduce the number of legs in tilt up applications.  By combining the RexRack lateral strut runners with CompRail you do not need a supporting leg set for each rail.  Contractors can space the legs 4’ - 6’ apart depending on the array height and choice of lateral strut runners (1-5/8” or 2-1/2”).  This feature reduces the required leg sets by half!   By reducing the support legs you also reduce the installation labor, roof penetrations flashings in direct proportion.  Comprail can support an 11' row of modules with a single leg, thus making intermediate rear legs unnecessary.
  • The ability to perform ‘seamless’ racking from the front side of the array.  All DSR systems require gaps between modules to insert clip sets when mounted from the front. This can impair the overall appearance of the module array.  Most manufacturers of DSR systems provide for a back-side seamless mounting method.  This, by definition, means that the contractor must have access to the back of the array.  In reality this typically requires that the contractor fasten modules to the rails on the ground and lift the monolithic assembly onto the roof - a very time consuming and awkward task.  SunEarth’s exclusive CompRail system allows the contractor to perform ‘seamless’ mounting without backside access.  All fasteners are on the topside of the array.
  • The CompRail system is unique in distributing the clamping load over the edge of the module.  Each point load created by the compression bolts is spread over approximately 8’ - 10” of the module edge by the rigidity of the upper rail.  The discrete DSR clip sets used in top-side mounting place the entire clamping force over the 1” width of their clips.  This concentrated point loading stresses not only the PV frame, but also the glass laminate, which may lead to premature failure if the bolts are over-tightened or high wind loads are encountered.

CompRail Residential Installation Manual (804 kb)