Good question, Jim.
We should all want our installations to work good and look good.
A lot of this consideration is purely aesthetic. As such, it doesn’t always have to be good, it just has to look good. What I mean by that is if there are some misalignments that can’t be seen from any vantage point, then it is not so critical to spend a lot of time making those perfect. I always look to see what vantage points there are from which a given installation can be seen and focus on making the installation look good to those vantage points.
Misaligned panels are only obvious where panel corners and edges meet. Your rack may undulate but as long as the panels meet up evenly that waviness is not readily visible. I don’t spend too much time checking a roof for flat—none of them are.
Two adjacent panels bolted to the same pair of rails almost always line up. The bigger problem occurs when you have two or more sets of rails. If the vantage point is from below and the upper set of rails is even slightly higher than the lower set of rails, that protruding upper panel edge can easily be seen. If, however, the upper set of rails is slightly lower, it is less obvious.
The key is to run a string line along the view axis to check to see of the pairs of rails are in alignment. Make the string as tight as possible. I space my string off the rail by a set amount—usually the thickness of a strut washer—and take another strut washer and slip it under the string at various locations. The reason to space the string above is to prevent the rail from subtly deflecting the string without you noticing it happening. You can also use a spare stick of rail or any long straight edge.
Lining up rows of panels is most critical if the installation can be viewed from the side. If the alignment gets bad at first without correcting it the error can quickly compound. The longer the row the worse it can get.
We set the first panel carefully and then take a length of rail and bolt it across the other end to hold a string line. Pick a reference point, usually the eave edge of the roofing—or any other straight line the eye might automatically compare the row of panels to—and use that as a guide to set your string. If the roofing courses waver you will have a harder time making it look right. Again, space the string off of the panel edge at both ends by a slight amount that is the same as an object you have handy for gauging. I use a strut washer or the thickness of a carpenter’s pencil.
If your row starts to deviate you can “steer” the panels gradually back into alignment. You can do this by leaving a gap between panels slightly bigger at the top or bottom to subtly correct for misalignment. The amount of extra space can’t be too much or the mid-clip won’t hold properly. You have about 1/8” to work with at any given gap. You can also subtly “stair-step” the panels up or down—in other words set a panel slightly higher or lower than the previous panel to get back on track.
If you see an upper row is higher at one point than the lower row you can stop stacking and adjust your rail up or down on the slotted feet.
We set the lower row first and then use disassembled mid-clips to make the spacing up and down pitch the same as across pitch.
One other thing: If you are using wider racking like Pro-solar or Snap-n-rack: Make sure the top of the rail is parallel with the roof surface. If the rail is cocked, when you tighten the clamps the panel moves as the rail rotates to contact the panel evenly. This can throw off your alignment. You can check this by setting an extra stick of rail across the tops of your installed rail and looking for gaps.
The process is tedious but if you check as you go and don’t let the error get too big the error can be corrected.
Jim, I hope this answers your qestion.
William Miller
Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com
CA Lic. 773985
From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim Gowdy via RE-wrenches
Sent: Sunday, September 29, 2024 7:55 PM
To: RE-wrenches
Cc: Jim Gowdy
Subject: [RE-wrenches] Racking on residential rooftops
Hello All,
I am trying to develop a good process for solar racking installs on roofs and ground mounts. I would like to be aware of any tricks of the trade. Right now the questions I have are.......
- How to find high/low spots on roofs
- How to get rails to the same level in all directions
- when mounting the solar panels, how to keep a straight line. So far a string line on the top and bottom is helpful.
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