[RE-wrenches] Mounting system for array on a metal roof

[Marco Mangelsdorf]

In Hawaii, we have a lot of steel-framed buildings with z-bar steel purlins
supporting the metal roof.  My attachment means of choice is using T-5
screws (#12 x 24 threads per inch).  These buggers are self-drillers with a
carbon steel shank and drill point and stainless steel hex head cap with
rubber grommet.  With a screw gun, you can actually zip these puppies
through your Pro Solar rail, through the roof metal and through the z-bar
purlin without the need to pre-drill.  I use two screws per attachment
point.  I've had this method studied by licensed structural engineer and he
has given me the thumbs up.  Between the rail and the roof metal, I use a 2"
square by 1/4" thick piece of Hypalon rubber to act as a dielectric between
the al. rail and steel roof.

I get the T-5 screws from Dynamic Fasteners and the Hypalon rubber strips
from MacMaster-Carr.

Marco
ProVision


--- You wrote:
We did four 6.8 kW systems for a commercial development with standard metal
building constructions. This building too had purlins 5' o.c. running
parallel to the ridge. After looking into it, we determined that #14 Tek
screws worked fine. The blow-mind was something around 1,400 pounds of
pull-out strength in the steel we were using (it varies with the gauge of
the purlin steel) per screw. (This is from memory and may be off.) We used a
single Tek screw per L-foot, with a 2" square of sealing bitumen membrane
under each foot, plus caulk after setting the screws.

Test your "red" steel for workability. Try to drill holes in an accessible
spot. See if this might work for you.

Allan Sindelar