William,
By gravity flashing i mean one of a bunch of newer systems that provide a metal
flashing overtop of the foot. The idea is to have it work like a shingle, where
gravity is on your side, not just sealants.
But here in lies the debate for me. A gravity is a nice backup, cause water
alway
Hi Benn,
Usually the solar array is not the limiting factor in my structural calcs.
The rails could span farther between feet, it is the point loads on the
building structure that is a problem. Unless it was designed for PV, the
uniform load of the snow is now getting transferred to the struct
Ray, we engineer every system using the ASCE structural load manual. Roof snow
load has to be below 113 SQFT (for high snow load modules) after taking the
ASCE slippery surface reductions based on slope.
thanks,
Troy Harvey
-
Principal Engineer
Heliocentric
801-453-9434
ta
Ben:
We do not put anything between the foot and the shingles. Maybe some EPDM
rubber
William
At 07:08 PM 11/13/2012, you wrote:
William,
Yeah the term 'gravity flashing' is new to me too.
While adding Lfeet for support without lagging them into the roof seems
like a reasonable solution t
Todd,
That is a tall pole. Hope those were back mounted and not the Solarworld 2.0
frames! How far into the ground did you go? With how much cement? Did DP&W
approve the engineering on that? My memory is they didn't approve TPM heights
much over 9'. The largest we've done are 15 module racks, b
the engineering called for 8" sch 80... and some super strong rebar in the
base. i subbed out the mount so dont have all the details easily accessible...
but if i recall, the hole is like 6' deep and 5 feet square. it seemed
inadequate to me, but it was engineered, so i guess good to go.
todd
Troy,
Maybe adding additional support to the trusses would allow you to spread out
the Lfeet a bit more? ...but then there is still that added cost!?!
QuickmountPV for one, makes a pretty solid case that any roof penetration needs
to be flashed if the waterproof integrity of a roof is to be ma
Thanks for the pitch info, very helpful. Are you using a heavy wall
thickness on the pole? I thought with DP &W we could only go 6 ft out
of the ground without increasing the pole size or adding bracing.
Ray
On 11/13/2012 4:21 PM, toddc...@finestplanet.com wrote:
ray,
this has been a lea
Troy:
I do not know what a gravity flashing is. Can you elucidate?
If you have adequate upload mounting strength and need more download
support, you can consider using additional L-fee that simply rest on the
shingles without penetrating the roof. We do that sometimes to take the
sag out of
HI Todd;
That's very interesting. What roof pitch does that happen? I'm
guessing that at a step enough tilt, the frame damage is alleviated?
Also on your tall pole mounts what pole design do you use? I've tried
telescoping type, and guy wires on tall poles.
Ray
On 11/13/2012 12:08 PM, tod
I have never had good results with roof mounted pv in our heavy (mount shasta)
snow area. the snow tends to creep down the glass and peel the bottom of the
frame off the module... and then the glass breaks as it has no support in that
area.
so, around here... i do pole mounts WAY up in th
Hi all,
We have been doing PV installs for years with L-feet and silicone without
problems ever. Even still, gravity flashings seem attractive in shingle roofs,
to provide a second level of security, and a more professional install (at
least in perception). But the cost of these systems in sign
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