Copper can get a pretty good oxide layer on it as well, but I'm not
versed in the science enough to know how any of that effects the
conductivity. Instead, I assume that the NEC has investigated corrosion,
and so we just follow the code. For plate electrodes (250.52(A)(7)), it
just specifies dimensions and thickness, and specifically mentions bare
iron or steel. 250.52(A)(3)(/1/) for Concrete encased electrodes (UFER)
also allows bare steel reinforcing rod, while section (/2/) allows your
#4 copper UFER.
Lacking further information, I just go with the code, and my own ground
impedance measurements over the years. My small sampling of
measurements has found steel rebar grounds and large steel pipe (4"D and
larger) to be under 25 ohms, while I have measured copper coated rods as
high as 700 ohms in dry soil. I haven't measure copper UFER or compared
it to steel, so again, I don't know. It might be better than steel, but
all are allowed by code.
Ultimately it might come down to soil and weather conditions for
different areas?
Ray Walters
Remote Solar
303 505-8760
On 6/25/21 10:35 AM, Dana Orzel wrote:
That’s why we use the Ufer, our AHJ assumes that once a layer of rust develops
this is not valid...........
Dana Orzel Great Solar Works, Inc.
C - 208.721.7003 [email protected]
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 <[email protected]> On Behalf Of Ray
Sent: Thursday, June 24, 2021 4:51 PM
To: [email protected]
Subject: Re: [RE-wrenches] Grounding Top of Pole Mount Array with a Ufer
We always put our assumption in our plan notes, based on our interpretation of
250.52(A)(7). AHJs have never questioned it, and we also tie the pole to any
rebar, so its all one big happy grounding electrode.
Ray Walters
Remote Solar
303 505-8760
On 6/24/21 6:49 PM, frenergy wrote:
Ray,
I couldn't agree more, its been my experience over the
years that using 20 feet of #4 rebar in a building's footing was
kosher and accepted NEC 250.52(3). There's a heck of a lot more
surface area in 8" pipe 5-6 feet into the earth than rebar in a
foundation footing. The ground at the bottom of the pole footing is
also more likely to be damper. Our AHJ has always accepted the steel
pole as a ground rod....common sense prevails sometimes.
Bill
Feather River Solar Electric
Bill Battagin, Owner
4291 Nelson St.
Taylorsville, CA 95983
530.284.7849
CA Lic 874049
www.frenergy.net
On 6/24/2021 7:31 AM, Ray wrote:
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 [email protected] 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 <[email protected]> On
Behalf Of [email protected]
Sent: Wednesday, June 23, 2021 9:33 PM
To: RE-wrenches <[email protected]>
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
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