[TowerTalk] [Bulk] Re: RF Ground is a Myth

Wed Jan 21 11:01:39 EST 2015

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 at 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 at 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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