O
Also - one theme is recurrent:
"If Ufer grounding alone was enough, the manufacturers of ground rods would go
out of
business. But a Ufer ground alone it is not adequate. Few buildings, even those
under
construction today are built to take advantage of the Ufer ground. It is common
to see the
use of "Ufer grounding" in military installations, computer rooms, and other
structures with
very specific grounding specifications. It is not common in most industrial
plants, office
buildings and homes. More common today is grounding to national and local
electrical codes.
This will involve one or more driven ground rods connected (bonded) to the
neutral wire of
the electrical service entrance. The purpose of this bond is what is known as
life safety
ground. It is used for many other things but the code required life safety
ground is why it is
there to begin with."
Where is that found..
I would say that in Southern California, virtually ALL new construction
for the last 20 years uses Ufer grounds (it's required by code in my
city of Thousand Oaks).
And of course, "grounding to national and local electrical codes" *is*
the Ufer (CEGR/CEE in the codes).
Rod makers won't go out of business. There's ample need for retrofits
and such, and as we've discussed, it's often cheaper, easier, more
practical to drive a bunch of rods than to pour concrete. (or to
evaluate the quality of a existing grounding electrode).
You're a contractor and you have a requirement on a job (not new
construction) to make sure what you're doing is grounded.. Do you pull
a few rods off the truck and have the crew drive them? The inspector
will certainly pass this.
Or do you go to the trouble of getting out the megger, driving rods for
test purposes (you gotta hook the "other wire" of the ohmmeter to
something), running all the measurements, calculating the resistance of
the existing ground? Nope.. You drive rods, the inspector signs, and you
walk away happy and paid.
BTW, I'd quibble with wikipedia's assertion about flashing into steam.
Unfortunately, the "reference" (number 8) isn't enough to figure out
where it came from. I suppose one could dig into the history of the
wiki page and figure it out, but...
On 21 Jan 2015 at 0:08, David Gilbert wrote:
You're going to need to duplicate the surface area of a typical Ufer
conductor, and you're going to need to somehow bond it intimately to the
bulk concrete. I'll be interested to see what your test setup is,
because I can't think of a legitimate method other than pouring some new
concrete on top of the old with the conductor embedded in it. Possibly
you're more clever than I.
And you should probably be prepared to compare it to alternate schemes
(ground rods, etc) to establish an appropriate baseline.
Dave AB7E
On 1/20/2015 5:22 PM, Brian Carling wrote:
I suspect it's not as conductive as some may have us think...
Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773
Tel: +USA 321-262-5471
On Jan 20, 2015, at 1:22 PM, David Robbins <k1ttt@verizon.net> wrote:
just remember when you do it to not use the point of an ohm meter probe.... it
is not easy to measure bulk material resistivity like in soil or concrete or
other types of materials.
you need to have some relatively large surface area to contact the material,
which is hard to do with already poured concrete.
Jan 20, 2015 12:59:36 PM, bcarling@cfl.rr.com wrote:
So far I am not convinced about using concrete. I'm going to do some resistance
testing on the concrete in my yard.
Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773
Tel: +USA 321-262-5471
On Jan 20, 2015, at 10:13 AM, Grant Saviers wrote:
If your house slab was installed correctly with a vapor barrier and/or foam
insulation, then it is insulated electrically from earth.
Tower bases make good Ufers as do perimeter foundations, so my towers and shop
both had the rebar set as Ufers when constructed.
I also noticed that a new service transformer I had installed is set on a concrete
vault that has a ground stub cast into the side. The power company used it, no
ground rods. I'd estimate its surface area in contact with earth as more than 16 sq
ft. Compare that to less than 2 sq feet for a 10' 3/4" ground rod.
Grant KZ1W
On 1/19/2015 6:52 PM, Mike Reublin NF4L wrote:
The electrician I had (who does a LOT of grounding work here) come out to
connect my tower ground to the service ground told me he would be glad to drive
the extra rods extending out from the tower, but doing so would add no benefit
at all. I have no idea if this is true or not. At some point, lacking personal
knowledge, ya have to take someone's word for it. My tower megged out at 4 ohms.
Mike NF4L
On Jan 19, 2015, at 8:29 PM, Brian Carling
wrote:
The advice varies about this considerably. This week is the first time I've
even heard of UF ER or conductive concrete!
The professional experts that I know recommend putting a 20 to 30 foot ground
rod into the ground at each corner of your house and connecting heavy gauge
copper conductors up to lightning rodsup on the roof.
It seems like if the only thing you need is a large area of this allegedly
conductive concrete stuck in the ground, why not ground everything to the
concrete slab your house sits on!!
Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773
Tel: +USA 321-262-5471
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