Uplift Wind Loading Values [RE-wrenches]

[Bill Brooks]

Joel,

My point goes back to your first message on Saturday (copied below). You
were making a case for why your design for SMUD was good and no leaks had
occurred. I was pointing out my first-hand experience with this design. The
fact that this design was implemented at PVUSA after your contract was over
and after you left Solec does not impact the relevance of the design.

The design was okay for that day and time, but it has been shown in
practical experience to have problems. My experience with your design that
was implemented at SMUD has convinced me to recommend against similar ideas
based on the weakness seen in the field. We live and learn.

With all do respect, your mounting system did have much fewer failures than
the first round design using the old NorthEast RES roofjack design with wood
screws. SMUD had to retrofit numerous mounting systems of that generation
because they were literally falling off peoples roofs. Wood screws were
pulling out of the OSB and the roof jacks were rolling over.

None of this is documented because it is not good news--and the rule was
"all the news that's good enough to print." I attended several presentations
by various presenters that said that SMUD never had any mounting
problems--that's just not accurate information.

Airing this information should not be seen as dangerous, but rather an
opportunity to learn and move on. For far too long, our industry has focused
on just telling the good stories. We need to tell the bad ones too so that
we don't keep making the same mistakes. I don't enjoy contradicting your
assessment and it is not in the least bit personal. My information clearly
shows shortcomings to the design that needed to be stated.

Best regards,

Bill.

-----Original Message-----
From: Joel Davidson [mailto:joeldavidson at earthlink.net]
Sent: Monday, March 24, 2003 9:58 PM
To: RE-wrenches at topica.com
Subject: Re: Uplift Wind Loading Values [RE-wrenches]


Bill,
I quit Solec September 1996 and never did work at PVUSA. What's your point?
Joel Davidson

Bill Brooks wrote:

> Joel,
>
> I'm talking about the exact Solec system that was installed on over a
> hundred homes in Sacramento. Identical mounting technique, identical
> hardware, same Ananda junction box, identical everything. This was not a
> SMUD design--it was the design that came as a result of the second Pioneer
1
> solicitation--this is, in fact, the design you were referring to.
>
> Bill.
>
> > >
> > > -----Original Message-----
> > > From: Joel Davidson [mailto:joeldavidson at earthlink.net]
> > > Sent: Saturday, March 22, 2003 4:17 PM
> > > To: RE-wrenches at topica.com
> > > Subject: Re: Uplift Wind Loading Values [RE-wrenches]
> > >
> > > Jeff,
> > >
> > > In 1994, SMUD was the world's biggest PV customer. The challenge was
to
> > > design
> > > and install the lowest cost grid-tied PV systems in the world on
> multiple
> > > sites.
> > > Siemens Solar and other bidders had little or no construction
> experience.
> > I
> > > knew
> > > that just about anything could be fastened to plywood if enough screws
> are
> > > used.
> > > I discussed my design with an American Plywood Association engineer
and
> > then
> > > I
> > > paid a registered engineer to review my design. We installed over one
> > > hundred 4
> > > kW PV systems on homes and 288 kW on churches totaling over 71,000
> square
> > > feet.
> > > Installations were limited to gable roofs in good condition with 1/2
> inch
> > or
> > > thicker plywood and composition shingles less than 10 years old. Solar
> > > panels
> > > with 7 Solec SQ80 modules (4.33 ft x 13.5 ft) were fastened to roofs
> with
> > 24
> > > each 1.5-inch #10 stainless steel wood screws through 0.25-inch thick
> > > aluminum
> > > mounting feet and into the plywood. We hired local electricians and
> > trained
> > > them
> > > how to make water-tight roof attachments. We paid a construction
> > specialist
> > > (retired general contractor with over 50 years experience) to fly to
> > > Sacramento,
> > > review our design and observe installers at work. To date, there have
> been
> >
> > > no
> > > roof leaks despite the worse rainy season in 100 years in 1994-95,
> several
> > > storms since then, winds over 80 mph at some sites and a few minor
> > > earthquakes.
> > >
> > > I used the same screw mounting on my own PV system, but I don't
> recommend
> > > fastening PV arrays with screws into plywood or other "out of the box"
> > > designs
> > > unless you are willing to do your homework, get stamped drawings and
> calcs
> > > from
> > > licensed engineers and pay a fair price for experienced supervision
and
> > > quality
> > > work.
> > >
> > > Peace,
> > > Joel Davidson

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