Designing a Solar Array-Ready Roof
BirchwoodBill
| Posted in General Questions on
I am working on a design for my personal residence. Trying to make it Solar PV ready? Is a dead load value of 5 pounds per square foot sufficient? Any suggestions for the transition from the roof (exterior) into an electrical conduit running through the house?
Location would Be Washington county, Minnesota. Zone 6A.
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Re the roof transition, "Soladeck" is one brand of what is frequently called a "solar combiner box" which is used to route cables from the power optimizers/mini-inverters into the structure.
Where are you located? There are a lot of local volunteer organizations (HAREI is one here in Hillsborough County, NH: https://www.harei.org/home) that can help with DIY installations.
Second the roof-mount junction box -- Soladeck seems to be a popular one, some of the racking companies also make similar.
On the structural question, the dead load would just be the sum of all the components of the solar system. BUT -- you may need to look at it as a series of point loads depending on how it's attached to the roof structure (ie, if it's secured every 3 or 4 feet, that load isn't really evenly distributed among the rafters). Also, there may be additional wind load considerations. Some of the racking manufacturers have design tools that'll help calculate the racking required and the loads transferred to the structure based on your location & structure details -- I used IronRidge, but I'm sure others have similar tools.
I believe it is a requirement that the racking system must be installed to distribute the load evenly across the roof rafters. Here's a picture showing just the anchors used to attach the racking to my roof, and another showing the combiner box just above the third rail from the top (installation by Revision Energy).
FYI, if your system uses power optimizers I believe the feed from the roof to the inverter must be in metal conduit in areas where it passes inside the structure. My installers used EMT within the structure and switched to PVC outside the structure.
If the feed for the roof is DC it needs to be in a metal raceway. If it's AC(micro inverters) then PVC or even Romex is Ok.
Soladeck is a great option.
Thanks, I will check the SolaDeck specifications.
Leaning toward S5 for the physical connection to the roof, but will take a look at Iron Ridge.