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Recently I worked with Jeff Randall, rack design engineer at DP&W,
on the design of a PT rack for 9 SW230s, a fairly large array, in a
bosque (desert river corridor near the Rio Grande) location. We
predicted a 6' underground water table and were limited to a 36" by 72"
augered hole, and Jeff worked with me to define a pole length and array
max tilt angle that would work within these limitations. What I was
surprised to learn is that Jeff didn't recommend any reinforcement in
this hole. He said that he followed the standards of the monopole sign
(billboard) industry, whose signs were substantially larger sails than
our racks, and their specs on similar holes didn't require
reinforcement of the concrete.<br>
<br>
I had always thought that a minimum amount of reinforcement near the
top of the hole would resist cracking that could lead to freeze-thaw
expansion and ultimately a loose fit around the pole, exacerbated by
seasonal wind buffeting, but apparently my concerns are unfounded.<br>
<br>
Some sort of steel is still needed to prevent rotation of the pole in
the hold, but this could be short rebar stubs, a welded nub, or even
holes in the pole.<br>
<br>
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<p class="MsoNormal" style=""><span class="il"><b style="">Allan</b></span><b
style=""> Sindelar</b><span style="font-size: 10pt;"><br>
<a href="mailto:Allan@positiveenergysolar.com" target="_blank"><span
class="il">Allan</span>@positiveenergysolar.com</a><br>
NABCEP Certified Photovoltaic Installer<br>
EE98J Journeyman Electrician<br>
<b style="">Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b style="">505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank">www.positiveenergysolar.com</a></span></p>
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<br>
<br>
Kent Osterberg wrote:
<blockquote cite="mid:4B9BBDAB.2060805@coveoregon.com" type="cite">The
need for rebar or not depends on how the pole is secured and on the
shape of the footing. If you are installing a pipe in a deep narrow
hole per most mount manufacturer's specifications, no rebar should be
necessary. Anything else will certainly require rebar and per
manufacturers' disclaimers should be designed by an engineer. For
example, if the installation will have j-bolts in the concrete with the
post welded to a plate held in place by the j-bolts, a full rebar cage
will needed.
<br>
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