Installation of 16 Panels - Wind Management Caribbean. 2 Install Options

[FullNuke]

Quick question for any wind professionals out there.

I am looking to install 16 4 rows and 4 columns solar panels with a QBase from iron ridge with the xr1000 rails.

Best wind management? 2 options

1. One piece completely flat with a 8 inch space underneath the solar and the concrete roof; all 16 solar panels connected to each other? I feel as if this will allow the wind to get under the panels and cause more pressure on the bottom of the 16 panels?

2. Or 4 inch tilt per row (4 panels each row connected to each other with 2 XRrails which will allow wind to move through each row? Independently.

4 solar panels connected in each row with 2 XR rails together X 4 rows.

Sun shade moves so I’m not worried about that. Both would work with the same efficiency.

Any knowledge on this?

 

[Stephen InGeorgia]

Not an expert, but if you want to limit the amount of wind under an array, why not put some blocking around it?
It sounds like even at a tilt, the low end would be 8" and the high end would be about 12". Why not take some wood and make a skirt that can be removed for maintenance. Would also keep the critters out.
How is the array anchored to the roof may be a better question because with proper anchoring, no wind should take anything away.

 

[Ampster]

I am not a wind professional, but Ironridge gives engineering calculations on their site. Use the highest wind speed in your area and it will calculate spacing of fasteners. You can run both scenarios. The heavier rail typically allows wider spacing of fasteners but the fasteners may need to go deeper.

 

[wpns]

So roof mount on a concrete roof? What's a concrete roof? Pictures?

If you have XR1000 rails and they are properly fastened down, they aren't going anywhere. I used XR1000 rails and HUG mounts on a (painted) shingle roof with offset 4' spacing, and I can't imagine any wind damage that doesn't take the roof off.

 

[Ampster]

....I can't imagine any wind damage that doesn't take the roof off.

I can imaging in some locations in the Carribean, winds from typical hurricanes exceeding 100 MPH. I don't know where in the Carribean hurricane winds are most likely but a friend spent a couple days in a concrete bunker as the eye passed through where he had anchored his boat. He said the concrete roof stay on but the damage was everywhere.

Did you use the Ironridge calculator? If so, what wind speed did you use for that design? My AHJ wanted to see those calcs and the assumptions that went into them. The Ironridge printout gave them everything they needed.

 

[wpns]

Did you use the Ironridge calculator? If so, what wind speed did you use for that design? My AHJ wanted to see those calcs and the assumptions that went into them. The Ironridge printout gave them everything they needed.

Kind of, I used that for a starting point, but since the weak point was the rafters and spacing I did the alternating-pitch thing and used lots of screws. It's as good as it's going to get for this install, and since I hired the AHJ to do the install, they could hardly complain. 8*)

Honestly don't remember the wind speed (125MPH?) but once you are into CAT5, it's "everything is blown away", so it doesn't matter if you could have used another couple of screws in each mount.

 

[FullNuke]

I used the highest wind speed 195 MPH and it spit out the flat roof attachments (1 inch tall) if I go with the XR1000 they are (3 inches tall); my concrete curb / parapet wall (if you want to call it) is 4 inches tall; so this would stay within the "concrete curb" and the 1.5" panel would be the only piece that would be level (1.5" above) of the concrete curb.

Mind you this will be 5 inches on all sides away from the concrete curb. Kind of crazy how it worked out that way. I can fit 16 panels within the "parapet wall" / "concrete curb" 4 inches high

Concrete roof meaning; its literally a 16 inch thick steel rebar slab of concrete.

I am thinking of going XR100 for .5" less height on the rail;

In Both applications - I doubt wind can get under the panels and lift them up; that is my only concern. All 16 panels will be tied together to these 8 rails with those UFO bolts while the panels lay completely flat.

 

[wpns]

Sounds like you have a plan, though how you do maintenance on an array that's 5 inches from the wall is an implementation detail.

Definitely want to see pictures when its done!

 

[FullNuke]

hopefully there is no maintenance; haha. Well reading more; flat panels require more maintenance; collects debris and doesn't clean with rain water; dust would sit on panel; I believe I will be going with a slight 6 degree pitch. Probably going to use the QBase now from Iron Ridge.

 

[Ampster]

I am thinking of going XR100 for .5" less height on the rail;

What I found was interesting in my relatively tame environment where the wind speed never gets above 50 MPH and even then there are some other buildings close enought that they slow the wind a bit. I started with the lightest rail and it required a lot of fasteners. By going to the next larger size rail the number of fasteners and hence roof penetrations was reduced. That was worth the extra cost of the larger rail for me. I don't know the answer for you but I all I am saying it might be worth looking at two design options. Your 4 inch parapet will cause a lot of turbulence for a few feet and that might reduce the uplift. I do not know if the calculator has that input but in my case, surrounding buildings and hills did seem to be factored in.

 

[FullNuke]

What I found was interesting in my relatively tame environment where the wind speed never gets above 50 MPH and even then there are some other buildings close enought that they slow the wind a bit. I started with the lightest rail and it required a lot of fasteners. By going to the next larger size rail the number of fasteners and hence roof penetrations was reduced. That was worth the extra cost of the larger rail for me. I don't know the answer for you but I all I am saying it might be worth looking at two design options. Your 4 inch parapet will cause a lot of turbulence for a few feet and that might reduce the uplift. I do not know if the calculator has that input but in my case, surrounding buildings and hills did seem to be factored in.

True - I'm actually going to use the tilt rail; the QBase seems like its only for flat installation. I was going to get different north and south height for the QBase but that would not allow the panel to be installed straight lol... silly me.