Answer: The distance between the mounting rails is determined by the module size and is highlighted in the module installation manual. For example, if you are installing the Solaria 320W modules in landscape, you can find on page 10 of the installation manual information that states if you are mounting in landscape mode, the rails should clamp within 11" of the edge of the panel on the short side. Noting the length of the short side of the panel listed in the datasheet, 41.6", you can find out what would be a suitable rail distance for your setup.
So, one way to do this would be to assume that you are going to clamp the modules 6" from each edge. Since the panel is 41.6" that means that the distance between both rails holding the same module would be (41.6” - 6” - 6” = ) 29.6". Then the distance between the next rail for the next row of modules would simply be about (6” + 6” = ) 12" plus maybe an extra half inch to an inch for a gap between the top row and the bottom row of modules.
There is some flexibility here given that you can clamp the modules anywhere from 0 to 11" from the edge of the module. So, be sure to use your best judgment when onsite taking into consideration the physical layout of the roof in front of you.
If you need further help, be sure to contact our team at Renvu or the Racking/Module manufacturer for more details.