We did a setup with the Snap N Rack rack on a roof once. We just used
the recommended galvanized SCH 40. Its basically a readily available
product. I would be careful with other types of steel tubing: make sure
it will fit the fittings. We actually retrofitted a Snap N Rack to some
existing pipe ground mount racking, and it turned out to be a slightly
different diameter. Big pain. 2nd, make sure its galvanized, which can
also slightly change the fit. 3rd, if the snow load is 100 lb/ sq ft,
your total array loading might be over 30,000 lbs. Is saving a few
pounds on the steel really worth considering? Seems like your post
bases on the roof are going to take quite a bit of engineering to
support the snow load.
Also, final note, the Snap N Rack setup doesn't do very good with uplift
wind loading. It just attaches with pinch bolts, so we had our one roof
rack get sucked off the roof in a hurricane. We drilled holes and
through bolted on the replacement array, but I'm sure we violated the
Snap N Rack 10 commandments by doing that.
I would consider other racks that might get the tilt with separate rows,
and be overall lower to the roof? Possibly a ballasted system?
Ray Walters
Remote Solar
303 505-8760
On 7/26/21 7:15 PM, Dana Orzel wrote:
Hey all!
I am proposing a [20] module, 35˚ tilt up array mounted on a flat roof
in snow country - Central Idaho. Its in town, trees behind & off to
the side a ways.
The SnapnRack design calls for [21] Pieces of 1 ½” x 21’ sched 40 pipe
+/-. I am trying to understand the need for sched 40 pipe on the
vertical components of this array. Though if the horizontal members
could be switched over to tube too that would be a big savings on
weight. I hope to eliminate the sched 40 for steel tube [stronger
metal thinner wall].
Without reinventing the wheel, has anyone approached this issue & how
did you address it?
Suggestions on beefy array systems that are lighter?
Spec.
[20] – Q-cell 340 watt modules. 5 columns of 4 modules.
Snow-Load - 100 PSF.
Tilt - 35˚ – The back & sides will be shrouded up to module on
vertical members to prevent wind uplift.
Wind - 90 MPH/3 sec microburst [though IF, this ever happened there
would be trees & garbage cans flying.]
Sched 40 -1 ½” pipe is 2.72#/ft.
1 7/8” steel tube is 1.25#/ft.
Maybe we all use schedule 40 pipe because that’s what we have always
done & locally available. Isn’t that’s what called recycled ignorance?
Looking for options. In todays world marketplace I am questioning this
approach.
Thanks in advance.
Dana Orzel Great Solar Works, Inc.
*C - 208.721.7003 d...@solarwork.com*
Idaho Contractor - # 028765 Idaho PV # 028374
NABCEP # 051112-136 www.greatsolarworks.com
<http://www.greatsolarworks.com>
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