[RE-wrenches] Pole Mounts - Frost/Conduit & Ledge

[R Ray Walters]

Hi Rich;

1) I never had a problem with conduit and frost heave, but then again, I haven't dug up all my work after 10 years either.
2) We did a mount exactly as you described, large slab with rebar into the rock at 45s, and bolt the pole to j bolts in the concrete.
I can share our design drawings if you like. We included gussets on the base plate, and the slab is large enough to overcome the tipping moment of the wind load.
Definitely want to keep the pole as short as possible on these. You may want to consider a ballasted design. We've done a few off grid versions that used the batteries as ballast.

R. Walters
ray at solarray.com
Solar Engineer




On Apr 16, 2011, at 8:55 AM, Rich Nicol wrote:

> Hi RE-Wrenches
> 1.       When installing pole mounts I have been running conduit into the side of the foundation and up the pole prior to pouring concrete.  The conduit enters the foundation ~ 18” to 24” below grade level.  We live in an area where frost depths are around 48” deep.  I have been told by folks in the construction industry that frost will not be problem with the conduit entry but I remain concerned that the conduit may be lifted, while the foundation which runs to below the frost depth, remains stationary thereby breaking the conduit.  Any insights?
>  
> 2.       Secondly, does anyone have experience with ledge in respect to pole mounts.  I know the answer is to consult an engineer, but I thought I would bring it up to the experienced folks in the trade first.  I have two mounts scheduled for this spring where I expect to hit ledge.  The first is a TPM with six 230 watt modules and the second is with eight 230 watt modules.  I’m expecting ledge to be relatively close to grade level, perhaps around 12 to 24” deep.  Ledge in these locations is solid (generally granite, sometimes gneiss or basalt).  My initial thought is to form a larger rectangular foundation with pins drilled at 45 deg angles into the ledge and tied to the reinforcing within the foundation.  A wide base on the pole would then be bolted to the foundation.  Any recommendations?
>  
> Thanks
> Rich
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