Hi Doug,
I had a customer's roof mount system break modules this spring after yet
another record Mount Shasta snow event. This one brought 8' in 10 days.
The situation here was 15 Evergreen 190 watt modules (rated for 80#/sq ft), on
a DP&W power rail mount, on a 6/12 pitch, comp roof. Ice dams were not removed
so the bottom edge of 5 module's frames were peeled off the glass... without
the frame's support, 2 of the module's glass broke. Evergreen did not warranty
the damage.
From Evergreen:
"The observed damage is attributable to weather related effects, not
manufacturing or workmanship issues with the panels.
You are correct, we do guarantee our panels for up to 80 pounds / sq. ft.
However, that is for a uniform load. The installation manual, page 3
(attached), has the following warning:
The maximum permissible loads apply to uniformly distributed
wind or snow loading. Care should be taken to avoid mounting
panels in areas that are prone to drifting snow, icicle and/or ice dam
formation."
I have come to the conclusion that the only real way to mount PV modules in
heavy snow country is on a pole mount with a steep winter angle and enough
ground clearance (minimum 6' from the bottom edge of the array to the ground)
to allow the snow to keep sliding off the array all winter. A roof mount might
still work, but it would need to be greater than ~8/12 pitch (not so good for
summer production) and accessible to manual snow removal in those critical
situations like we had here a couple of weeks ago.
One of my most difficult challenges is trying to design my installations to
mitigate winter snow damage. I realize very few list members have to deal with
these kinds of severe conditions, but any feedback on my empirical conclusions
would be welcome.
Todd
On Wednesday, April 13, 2011 8:44am, "Doug Wells"
<[email protected]> said:
>
>
> Wrenches,
>
> Can anyone recommend a panel that is built with more strength or
> ability to handle greater load.
> I am installing on a shallow pitched roof and am concerned about snow
> build up in this particular location.
> I know you guys out in the Sierra's get a lot more snow than we do.
> What modules are up to the challenge?
> Are there any new military spec modules like the old MSX 120's?
> Any experience or guidance is appreciated.
>
> Doug Wells
> Morrisville, VT 05661
> NABCEP Certified PV
> Vermont Solar Partner
> The Solar Specialists
> www.thesolarspecialists.com
> 802-498-5856
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