Manually Specifying Racking for Roof Mounted Systems (Part 1)

Although there are a host of online tools to aid in the design and creation of a racking bill of materials (BOM), it is important to understand what is going on behind the scenes to check your work.

Panels can be arranged in either portrait (longest side is vertical) or landscape (longest side is horizontal) position. Further, rails can be run either north/south (vertical) or east/west (horizontal). As such, the four permutations below are available:

Panel/Rail Orientation:

The formula for determining the length of a particular row or column of panels is as follows (where x = number of panels in column/row):

(x)(length OR width of panel, depending on portrait or landscape) + (x - 1)(space required for each mid clamp) + (2)(space required for each end clamp) = required length of row or column

Clamp spacing:

IronRidge: ¼” for mid clamps, 1.5” for end clamps

Unirac: 1” for mid clamps, 1.5” for end clamps

For example, to determine the space required for a single row of 10 Canadian Solar CS6P-265P panels (dimensions: 64.5 × 38.7 × 1.57 inches) in portrait orientation using IronRidge racking, the equation would look like:

(10)(38.7”) + (10-1)(0.25”) + (2)(1.5”)

= 387” + 2.25” + 3”

= 392.25”

The E/W width of the array is 392.25” (32.6875’) and the N/S length of the array is 64.5” (5.375’, equal to the length of the panel).

With this information, we can determine the racking BOM for this array.

Published
3 years 10 months ago
Written by
Conor Walsh
Support topic
Products
Solar panel
Racking and mounting
Installation
Roof mount
Ground mount
Support keywords
racking layout
roof racking
rail
l foot
flashing
mid clamp
end clamps