[RE-wrenches] Racking on residential rooftops

[William Miller]

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-bounces at 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.



-- 

Jim with Gowdy Electric

Cambria, Ca 93428

business  805 927 2630

cell  805 975 5279
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