[TowerTalk] Bonding entrance panel to utility ground question

[K8RI on Tower talk]

----- Original Message ----- 
From: "Jim Lux" <jimlux at earthlink.net>
To: "Jim Brown" <jim at audiosystemsgroup.com>; <towertalk at contesting.com>
Sent: Sunday, March 26, 2006 9:03 AM
Subject: Re: [TowerTalk] Bonding entrance panel to utility ground question


> At 09:08 PM 3/25/2006, Jim Brown wrote:
>>On Sat, 25 Mar 2006 18:46:56 -0800, Jim Lux wrote:
>>
>> >Here is where it gets tricky.  You'll have to look up the code sections 
>> >to
>> >see if you can bond the antenna lightning protection ground to a 
>> >electrical
>> >safety ground.  I'm going to guess that it's not a good idea.
>>
>>I will differ with you on that one, Jim. Under NEC, and most electrical
>>codes, ALL grounds within an installation are required to be bonded 
>>together,
>>including the lightning protection system. NEC (and most codes) state that
>>the lightning protection system ground cannot be the SOLE earth 
>>connection.
>
Here there would be two issues.
Our electrical code and the inspector will insist the cable that ties into 
the tower and station ground tie directly to the service entrance ground 
rods.  It may not tie to the ground wire or be shared as in a ground to the 
well.

I'd not want to share the well ground either. It's a good way to lose a 
submersible pump. Here, wells (the pump) may only be grounded back at the 
panel. It is, after all, and electrical device powered from the panel.

The well does nothing for RF and it does make a good sink for a lightning 
strike if the rest of the system is not up to par.

>
> I'll agree with that.  All grounds (in the same building) MUST be bonded
> together. My comment (which, now that I read it, was poorly worded) was
> whether it's "legal" to bring that lightning ground (from the polyphasers)
> *into the middle* of the "grounding conductor" (greenwire ground) from the
> well pump.  (A "T" intersection, if you will.)

We can not share anything through the green wire. Roger Halstead (K8RI and 
ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com


>
> I think you'd be better off running a separate bonding conductor from the
> "lightning ground rods" to the "utility entrance ground", rather than
> sharing part of the run of the well pump grounding conductor.  What I 
> don't
> know, off hand, is whether the code would even allow such a sharing of the
> conductor.
>
>
>
>>In general, ALL grounds and ground electrodes in a given installation 
>>should
>>be bonded together, and, as you have so elequently observed, making that
>>connection THROUGH the building is not the smartest idea. BUT -- as has 
>>also
>>been observed, lightning has HF spectra, and even the slightest inductance 
>>in
>>the bond can develop some very high potential differences and generate 
>>arcs.
>
> And there's the tradeoff..
>
> Of course, he has a bunch of ground rods right at the polyphasers, so one
> thought might be that you want a fairly inductive, but code legal,
> connection between the lightning ground rods and the utility ground
> rods.  That way, in normal operation, you don't have an issue with grounds
> at different voltages, etc., but when the lightning hits, the transient
> isn't coupled (as well) into the building's green wire grounding system.
>
> (Or, into that nice pump immersed in water a hundred feet down the well)
>
>
>>I like the recommendation of getting that antenna to earth by the shortest
>>possible route (and without bends), then bonding it by the lowest 
>>inductance
>>means to all other earth connections and building grounds.
>
> But what if the ground at the antenna entrance is "better" (lower
> impedance, etc.) than the "code ground" at the utility entrance.  This is 
> a
> scenario that I think is actually quite common.  The code ground is
> designed for 60Hz, not RF, and the inductance is not usually
> considered.  On the other hand, hams obssess about getting a good RF 
> ground
> (all those "how do I most effectively string this 100 pounds of copper 
> wire
> I got at the hamfest" articles and posts and websites), which, to a first
> order, probably is a better lightning dissipation ground than the utility
> ground.
>
>
>>  But if the bonding
>>path is a long one around the perimeter, L can be quite high. This why 
>>W8JI
>>has correctly observed that the best place to bring antennas in is right 
>>next
>>to the power service (and power earth electrode). Unfortunately, that 
>>isn't
>>always practical when we're not building from scratch and can't make that
>>choice for the location of the ham shack.
>>
>>Jim Brown K9YC
>
>
> Jim, W6RMK
>
>
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