[TowerTalk] grounding quesitons: Ufer, strap, exothermic welds

Sun Apr 17 18:58:18 PDT 2011

Agreed Roger!  They work well in any type of soil or rock. The theory is to 
dissipate the strike energy to as much earth as possible. Radials, with 
properly spaced
ground rods are a good way to go!

73
Jim W7RY

--------------------------------------------------
From: "K8RI on TT" <k8ri-on-towertalk at tm.net>
Sent: Sunday, April 17, 2011 6:38 PM
To: "Bert Almemo" <balmemo at sympatico.ca>
Cc: <towertalk at contesting.com>
Subject: Re: [TowerTalk] grounding quesitons: Ufer, strap, exothermic welds

> On 4/17/2011 5:28 PM, Bert Almemo wrote:
>> I have a friend ready to put up a new tower and we're planning the 
>> grounding
>> system.
>>
>> How about placing a big ground plate at the bottom of the hole for the 
>> tower
>> foundation before pouring the concrete? Should the tower, ground plate 
>> and
>> the rebar cage be connected together? Good or bad idea?
>
> I have to go along with others that have already weighed in.  It's just
> not worth the effort or expense, particularly when you realize that big
> block of concrete is a very good ground and if large enough becomes a
> UFER ground.  I believe in adding a radial system with ground rods,
> which I did here as we have moist soil and that gives a very large
> ground system which has proven effective.
>
> 73
>
> Roger (K8RI)
>
>> 73 Bert, VE3NR
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: towertalk-bounces at contesting.com
>> [mailto:towertalk-bounces at contesting.com] On Behalf Of K8RI on TT
>> Sent: Sunday, April 17, 2011 5:12 PM
>> To: towertalk at contesting.com
>> Subject: Re: [TowerTalk] grounding quesitons: Ufer, strap, exothermic 
>> welds
>>
>> On 4/17/2011 2:06 PM, 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.
>> A while back I watched a training film from either NWS or NOAH that 
>> showed a
>> lightning strike that had not just cracked, but blown part of a system 
>> apart
>> BUT and and emphasize the but, stranded wire (either  0 or
>> 00) had been used and it was in a wet location IIRC. Just what happened 
>> they
>> weren't sure, but it was an extremely rare event and I think we need to 
>> keep
>> in mind there is no 100 % guarantee against lightning, no matter what we 
>> do.
>> That means we *always* end up playing the odds and approaching 
>> diminishing
>> returns as we make our systems more robust and costly.
>>
>> OTOH every proper step taken increases the odds in our favor.
>>
>> Considering the odds I'd not worry a moment about tying the rebar in the
>> concrete to the grounding system.
>> I think it's a positive in our favor rather than a negative.
>>
>> I would make sure the rebar did not come within 3 to 6 inches of any 
>> surface
>> of the concrete (code requirement I believe) and I would prefer solid 
>> copper
>> instead of stranded, but even stranded can be sealed.
>>
>>
>>
>>> 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.
>> I think they are wrong to call it a myth, but it's such a rare event AND 
>> the
>> procedure actually increases the odds in our favor so, it would not be a
>> concern for me.
>>
>>> 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?
>> Mine has taken at least 17 direct hits and there's not even a chip in the
>> concrete.  It was getting to be a regular thing, but nary a strike (that 
>> any
>> one has seen) in the last 3 years.  This will be the 4th summer. Who 
>> knows
>> what it will bring.
>>
>>> 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.
>> Probably because those who have seen it were so impressed they let the
>> rarity of the event outweigh the effectiveness of the procedure.
>>
>> 73
>>
>> Roger (K8RI)
>>
>> _______________________________________________
>>
>>
>>
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