LaMar Alexander wrote:Just wanted to share my new 400 watt solar installation for ideas.
Just FYI, what we do on a lot of our elevated ground mounts rather than buy commercial rail is just use SunModo end and mid clamps with long (3-4") stainless self tapping screws into purlin. (Imagine a pole barn without any roof sheeting, but with the purlin spaced at the modules' rail spacing.) A 30' stick of 6" C purlin
should run you around $45-50, and will make a pair of 15' rails to hold 4 (39" wide - most of the common 230-290W ones) modules as stable as whatever you mount the purlin to. Not sure who sells small lots of the SunModo clamps, but any that will take a #14 screw should work. I don't think we've ever tried it with 4" C purlin, but for such a short span (we're usually trying to maximize span on these for rows of 10-20 modules) it may work fine. General rule for me in figuring row/rail lengths is to assume a 1" gap between modules for the mid clamps and 2" on each end for the end clamps to be solidly on the rail. There are 1/2" and 5/8" mids out there, but 3/4"-1" is more common.
I wouldn't really recommend it, but I know some have used the long screws and stainless fender washers in place of mid clamps with some success. Part of the issue there is the washers being so big as to shade the edges of the cells near them.
We've only had one of those fail due to wind, and that was repeated 100+mph straight line gusts coming right in under the modules. Designing for that would end up being so overengineered as to be cost prohibitive for nearly anybody.
1
