Usually a steel pole in concrete has enough surface area to qualify as a
plate electrode under 250.52(A)(7). It needs to be at least 2 sq ft and
1/4" thick, and have an electrically conductive surface. So we just
drill and tap our ground connection into the pole, near the combiner box.
Ray Walters
Remote Solar
303 505-8760
On 6/24/21 8:16 AM, Dana Orzel wrote:
For all of our free standing arrays we now use a Ufer clamp to the rebar either
cage or just anti spin rebar that is welded to the pole in the concrete, with
#4 braided copper up to the pole combiner box, inverter, etc. for our ground.
With a pole mount & a concrete base it is way easier & less expensive than a ground
rod, & the inspector seems happier with this approach.
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
"Responsible Technologies for Responsible People since 1988"
Please consider the environment before printing this email.
-----Original Message-----
From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> On Behalf Of
palumbo1...@gmail.com
Sent: Wednesday, June 23, 2021 9:33 PM
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] Top of Pole Mount Array on Ledge
Ben,
There is a way if the ledge is solid and true. Twice I have done the following
with ledge at 18” to 24” below grade. Excavate down to ledge, drill down into
the ledge and you will determine the suitability of the following method. Drill
for a pattern of many rebar penetrations in to the ledge. Drill to a reasonable
depth (as deep into the ledge as you are able) in my case it was based on our
drilling tool and bit length capabilities. We used a large sono tube. 42” as a
recall, both of these jobs were over 12 years ago and my recall on the exact
size may be off.
Determine the best adhesive product to use in your drilled holes for the rebar,
again my memory fails as to what we used based on recommendation from a local
civil engineer. The sono tube height above grade was determined to be 2’ for
one TPM12 and 3.5’ above grade for a TPM16. Depth down to the ledge determines
how high above grade you need the concrete footing/base. Use rebar lengths that
will end a few inches below the finished surface. For grounding you can coil up
ground wire and lay it on the surface of the ledge before your concrete pour. I
ran the ground wire through a short length of 1/2” or 3/4” PVC conduit, to
protect the copper ground wire where it comes out of the concrete. Place the
conduit coming out of the concrete with the ground wire just to the side of
where the mounting plate base for the TPM will be and fill the PVC conduit with
a good caulk sealer to keep air and water out of this hole as a nexus of
concrete, and air will corrode the copper. The TPM’s for those two jobs were
made of 8” SCHD 80 steel, we had a large plate welded to the bottom with 4
vertical side supports on the pipe up about a foot. Place the appropriate sized
anchor bolts in the concrete pour to match your TPM base. Both of these TPM’s
have worked out well over the years. Local conditions will determine the
suitability of this method.
Sent from my iPhone
On Jun 23, 2021, at 6:39 PM, Ben's Solar and Battery <b...@mcfeeters.net> wrote:
Hi Wrenches,
We typically use SunModo ground mounts with ground screws which we can put just
about anywhere as our screw guy has a rock drill.
We have one customer who is dead set on a top of pole mount array and will not
settle for a typical ground mount with multiple posts.
There is shallow ledge all over her property and we feel that digging multiple
large holes to find one spot where we might be able to get deep enough would be
a waste of time and resources. We have called an underground locator who uses
ground penetrating radar and he scanned a few spots, but was unable to give us
a good location based on soil types.
What are you guys doing in this situation? Are there any alternatives, such as
a pole mount with large base and ground screws?
I hate saying it can't be done!
Thanks!
Ben
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