How to Mount Unirac SolarMount Tilt Legs
A brief summary on the installation and sizing of Unirac Solarmount low profile and high profile tilt legs.
Unirac Solarmount low profile and high profile tilt legs are great options for both roof mount and ground mount solutions. At first sight, it seems difficult to size the number of legs and rails, however it's pretty simple once you know what to look at.
I'll seperate the article into two sections for your convenience:
1) LOW PROFILE TILT LEGS
Mount the modules in portrait. Calculate the necessary rail length:
n= number of modules, w=width of module, 1" spacing for mid clamps, 3" spacing for end clamps
(n x w) + (1"x (n-1)) + (3" x 2)= rail length
The most difficult part is to decide how many tilt legs you'll have to use. The way to calculate is pretty straighforward. If you know the length of the rail you are going to use, just refer to the table below. Please make sure that, this table is for zones with mild climate (no strong storms, no high snow loads). The more tilt legs you use, the more sturdy your array will stand, tough you'd spend more time on installation which also means more penetration on the roof.
Make it safe but not too much. I'd read the Unirac Code Compliant Installation Manual (pdf) to have an idea on the effects of snow load and wind load.
|Rail length per row||Low profile Tilt legs
required per row (min.)
|48" to 106"||2|
|120" to 180"||3|
|192" to 216"||4|
|226" to 288"||5|
|300" to 336"||6|
|348" to 408"||7|
|420" to 432"||8|
The low profile tilt legs come in three dimensions: 12", 30", 44". They are all telescopic and the dimensions refer to the maximum leg length. The taller the leg is, the higher the tilt angle you'd achieve.
Here is an example: Let' say we are using 4 modules with a length x width of 65" x 32". I want 20 degrees tilt angle.
(4 x 32") + (1" x 3) + (3" x 2) = 137 " (The available solarmount rail size is 144")
I have to use minimum 3 tilt legs.
To achieve a tilt angle of 20 degrees, here is what I do:
tilt height= module length x sin(20) = 65 x sin(20) = 22.2 inches. That means, a 30" tilt leg is sufficient for what I need.
2) HIGH PROFILE TILT LEGS
The modules are mounted in landscape mode and the rails are oriented north-south direction. The rail length is calculated the same way and you can refer to the above table for the minimum number of tilt legs.
If your rail length is tall, then you'd have to use the two-leg high profile tilt leg system. Otherwise, you can use the one-leg system. Please refer to the table and the pictures below to determine the footing bolt and L-foot spacing* for your solarmount rail set.
Please comment on the article if you have any questions.
|1-Leg System||2-Leg System|
|*Spacing for 70%||*Spacing for
*Please refer to below images for 'spacing' 70%, 45% and 40%.
Great article, thanks. Question, when you put together the Unirac tilt legs, is it required to use a flanged washer with every bolt? Do you need to use a washer to add additional support on the bolt attached to the l-foot? Do you need to use a wash with the inside bolt?
A typical fender washer would suffice. The attached drawings are from the installation manual (pdf).
I am looking at using the 104" High Profile Tilt Legs for my installation with a 168" rail length. I am having trouble calculating how the angle range can be between 18 and 55 degrees. Is the table accurate in this respect? How many sections are in each of the legs?