a. Neither of those codes apply to a non-electrically energized
structure, that's why. I have, however, glanced through the Napa County
(where you live) regulations online, and while I didn't find anything
specifically mentioning tower installations, those regulations are
extremely comprehensive ... almost to the extreme. They even specify
the size wire required for bonding ham radio equipment to the SPG. I
would be truly astounded if Napa County did not somewhere specify that
the rebar cage in a tower base needed to be bonded to the tower.
b. The instances of cracked tower bases that I've read about, and the
only one quoted by I.C.E., was where the tower had NOT been bonded to
the rebar cage ... i.e., no Ufer ground existed, or that the Ufer ground
was of insufficient size. In any of those three instances you speak of
was any sort of investigation performed to see if the tower had been
connected to the rebar cage? I doubt it. In fact, the existence of
those three cracked bases most likely demonstrates exactly why, in
contrast to your original advice, the tower should indeed be bonded to
the rebar cage. You can't blame the Ufer for the failure if the Ufer
didn't exist in the first place.
c. Yeah ... it's a myth. Here's another link for your perusal .....
http://www.comm-omni.com/polyweb/ufertower.htm
Dave AB7E
On 4/17/2011 1:55 PM, Robert Harmon wrote:
> Dave,
>
> Wow, did I hit a nerve ? Didn't mean to stir up deep rooted
> feelings on this subject.
>
> Lets take one thing at a time. Our local building code does not specify
> connecting the tower to the rebar cage. It is also not required in the
> national
> Uniform Building Code or the NEC.
>
> In building department inspections I have seen three separate instances of
> cracked concrete tower footings caused by lightning strikes. Two common
> denominators in each of these was the lack of tower grounding to a ground
> rod(s),
> and a required building permit was not attained (which would have prevented
> this)
>
> Urban myth ? hihi
>
>
>
> Bob
> K6UJ
>
>
>
>
>
>
>
>
>
> On Apr 17, 2011, at 11:06 AM, David Gilbert wrote:
>
>> Again?? Seriously? That myth has been debunked so many times, both
>> here and elsewhere, that I can't believe people are still perpetuating
>> it. I've issued this challenge several times before and nobody has ever
>> responded ... please quote one single URL or technical document that
>> describes a verified instance where lighting passing through a proper
>> Ufer ground , or any conductive element inside a buried concrete
>> structure whatsoever, cracked the concrete. You'll find instances where
>> a direct lightning hit to the OUTSIDE of a block of concrete caused
>> damage (buildings, bridge abutments, etc), but not via a Ufer system of
>> sufficient size and construction.
>>
>> Check out the I.C.E. technical note on the subject if you don't believe
>> me. It's not difficult to find on their website ... it even uses the
>> word "myth" in the subject title.
>>
>> Besides ... just think about it for a second. There are thousands of
>> tower installations with a tower base buried in the concrete. What
>> would be the difference, other than beneficial spreading of the current,
>> if the tower was also properly connected to the rebar cage?
>>
>> Lastly, connecting the tower to the rebar cage is REQUIRED by most
>> zoning regulations.
>>
>> I'm honestly curious why certain urban legends, like this one, seem to
>> have such staying power in ham radio. I suspect it's because the
>> purported consequences sound dramatic even if they happen to be totally
>> unfounded. The more likely they are to fire up our emotional responses
>> (fear, indignation, surprise, etc) the more likely they are to be
>> believed ... and worse, passed on to others. Most of the stuff on
>> Snopes is like that. If you want to create an immortal misconception,
>> be outrageous about it.
>>
>> Dave AB7E
>>
>>
>>
>>
>> On 4/17/2011 8:19 AM, Robert Harmon wrote:
>>> Mat,
>>>
>>> Sounds like a very good ground system. I have a question on one thing.
>>> As part of your grounding system you mention connecting to the rebar. I
>>> assume this is the rebar cage that
>>> will be cast in the concrete base. I think this is a no,no. A lightning
>>> strike can
>>> conduct thru the rebar and crack the concrete.
>>>
>>> Bob
>>> K6UJ
>>>
>>>
>>>
>>> On Apr 17, 2011, at 7:24 AM, Mat Eshpeter wrote:
>>>
>>>> I am about to pour concrete for the base of my HDX589 tower. I am going to
>>>> go with a Ufer ground as well as the Polyphaser recommended eight 75'
>>>> radials with multiple ground rods (8' rods every 16'). Location is on top
>>>> of a 1600' ridge in WV and lightning is a very real concern. My QRZ web
>>>> page gives a feel for the location.
>>>>
>>>> To build the Ufer ground, I am thinking about connecting a single bare 2/0
>>>> stranded copper wire to the rebar. Questions:
>>>> 1) is one enough?
>>>> 2) how do I properly connect the copper to the rebar? Is exothermic weld
>>>> the only way? Any problem with dissimilar metals?
>>>> 3) how should the copper exit the base slab - above grade or below grade?
>>>>
>>>> Also, seems that copper strap is the preferred ground material for
>>>> connecting rods together. Will 0.032" thick strap have significantly
>>>> better longevity than 0.022" strap? I am refering to the strap sold by
>>>> Georgia Copper. Copper is expensive and I don't want to invest in copper
>>>> that won't add any value to my installation.
>>>>
>>>> Where can I find exothermic weld products to connect copper strap to 5/8"
>>>> copper clad ground rods? I am exhausted reading Harger, Erico, Terraweld
>>>> info, and can only find wire-to-ground rod products, no strap-to-rod
>>>> products.
>>>>
>>>> 73
>>>> Mat
>>>> KK1C
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>>
>>>>
>>>>
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