Uplift Wind Loading Values [RE-wrenches]

[Joel Davidson]

Dear Mo,

I don't even trust fasteners into framing members without testing for strength.
When I train installers, I tell them to grab the solar array and try to tear it
off the roof to make sure it is fastened securely. A good installer has no
doubts about the strength of his or her attachments.

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 (made by
Steve Robbins founder of Solar Outdoor Lighting and SEPCO) was the only
operating street light in town. Earlier that day, the police station wind speed
indicator recorded 228 km/hr (141 mph) gusts.

Best regards,
Joel Davidson

Mo Rousso wrote:

> I agree that we have to hit trusses.  OSB and ply have liabilities,
> especially if we want the systems to last.  I went on a service call not too
> long ago after a major wind storm to inspect a system installed (not by us)
> on an asphalt comp roof.  It was a compound array with a portion flush
> mounted and a portion tilt mounted.  The tilt mounted portion of the array
> had tore out all fasteners, except for one, which was properly lagged to the
> truss.  You could literally see where divots of OSB had been pulled out.
>
> I would say that 80 to 90% of our install time is spent on the roof and 50%
> of that time is spent on properly locating, lagging, and waterproofing the
> jacks.  Probably the second most time consuming task is in doing proper
> equipment grounding of the array and racks.
> --
> Mo Rousso
> President
> HelioPower
> Renewable Energy Systems
> Remote Power Solutions
> mrousso at heliopower.com
> www.heliopower.com
> 760.451.9374

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