PV arrays, wind and teaching [RE-wrenches]

[Joel Davidson]

If you want more better, more safer PV systems, then teach more. Here is
a verbatim letter from a PV system owner-installer. My thanks to
everyone who posts information on the world wide web. Special thanks to
UniRac for posting their Code Compliant Installation Instructions at
http://www.unirac.com/pdfs/tb103.pdf

Hi Joel,

I always appreciate your advice, so thought I'd try another question
with you.

During the last round of winds, we took several 90 mph gusts here.
Enough to lift up a firmly anchored metal garden shed weighing about
250 pounds and pop it over a 6 foot flagstone wall into our neighbor's
yard.  Just trying to give a feel for the excitement "below the passes
and canyons" out here.

The PV panels, rack and mountings were apparently solid as a rock.
They're tilted to lat+15 right now for the winter.  I overdid the
mounting instructions a bit and used 3/8" x 6" lag screws to go into
2x6 rafters.  I think the instructions indicate 5" hardware, but I had
to go through sheeting plus slats, so thought I had to make up the 1"
of difference from the instructions.

Should I worry about this?  Having the panels tilted up to act like a
sail, I mean.  Nothing happened to the roof or the PV installation,
but I'm walking on pins and needles each time the wind kicks up again.
I just think you might have a few words based on your experience in
construction and the number of PV installations you seen installed.
Since there was no damage (that is apparent from the ground), I'm
assuming that I'm just a worry wart.

Dear ,

It is natural for even the best installer to worry when the wind is
howling. You did the right thing from the start by securely fastening
your PV array. You are also doing the right thing by inspecting your
equipment regularly and after each wind storm. I teach installers to
fasten the array to prevent it from flying off and killing the person
who they love the most. Then I grab the array and try to rip it off the
roof just to make sure.

Here's a true story about PV in the wind. After the 1992 Homestead,
Florida hurricane a lady called the police station to ask why her lights
were out. When she was told that power was out in the whole town, she
told the police that the street light near her house was lit. The police
investigated and, sure enough, solar powered light with a pole-mounted
solar module and battery box was the only operating street light in
town. Earlier that day, the police station wind speed indicator recorded
228 km/hr (141 mph) gusts.

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