[BVARC] Lightning

Robert Polinski emdhouston at cebridge.net
Thu May 27 18:24:07 CDT 2021


The intersystem grounding block  was required a couple of code cycles ago.
Some cities take several years to adopt a code cycle, so it may or may not
be required on your house. An many inspectors just do not keep up with
current code. What AT&T did is code compliant. AT&T mostly does it
correctly, not so much for the cable co. and rarely for the sat installers.
As for the long run between the house rod and the ham station, not a
problem, I would maybe up size the wire to #4 but even with smaller wire,
the object is to bond the 2 together to eliminate any voltage differential
between the 2 grounds. The  impedance of a #6 wire is less than the romex
snaked thru your walls. If you install a bonding wire it can be uninsulated,
just do not run it thru any metallic piping as the pipe will act as a choke
and impede the current flow. Robert 

 

From: BVARC <bvarc-bounces at bvarc.org> On Behalf Of Westley Clavey via BVARC
Sent: Thursday, May 27, 2021 5:29 PM
To: BVARC <bvarc at bvarc.org>
Cc: Westley Clavey <wesclavey at aol.com>
Subject: Re: [BVARC] Lightning

 

After all this discussion, I went on a field trip around the house, garage
and attic to note the grounding points.� 

There is no intersystem grounding block, per se.� There is a #6 ground
wire from the AC Service breaker box to a ground rod located at the back of
the garage.� When AT&T installed our cable, they ran a second #6 wire to a
clamp they added to the same ground rod.� So they are, in effect, grounded
to the same point.

There is a clamp on an exterior cold water pipe near the kitchen, but I
cannot figure out where that wire goes.� This is a very heavy stranded
copper cable in this clamp, probably 3/8" in diameter.

The service ground is on the back of the garage.� My shack is on the
diagonal corner of the property, probably 150-160' away in a straight line
across the yard, the patio, and around the garage.� I have no idea what
the right way to connect them would be... if I wanted to run a wire from my
station ground to the service ground, It would probably be close to 200'
long, taking into account the things I need to go around.� Is that a low
impedance connection?

I was hoping that I could locate that very heavy line up in the attic
somewhere with all our utility equipment.� Hoping that it, too, is
connected to the service ground, it would be easier to connect my station
ground to that, but no luck.� I don't know how to proceed.

On 5/27/21 2:25 PM, Robert Polinski via BVARC wrote:

Most lightning damage done in a house is� due to a poor grounding system
on the AC service. All service panels should have at least 1 8ft ground rod
with a min of #6 ground wire going to the panel board. The size of this
conductor is dependent on the size of the service. In many cases, this
ground is missing, the clamp has rusted off, or is just making a poor
connection. In many areas, the copper thieves have cut the pole grounds,
making your rod the last defense before the surge hits your home. Ground
rods need to have an impedance of lest than 25 ohms, sometimes more than 1
rod is needed to get this. Warning, before you do any checking or service on
your grounding system, turn off your main breaker & test your ground wire
with a clamp on amp meter. If it indicates any current, it is a sign that
the power co. ground is bad & working on it could cause electrocution. Call
an electrician. 

����The second issue is the failure to bond all grounds together.
Newer electrical services are required by code to have a intersystem bonding
block. On this block it has terminals for bonding CATV phone & any other
systems to the service ground. You ham station grounding system MUST be
bonded (connected) to this system with a #6 ground wire. This is a NEC code
requirement and a must to prevent station damage �& possibly a fire. If
you do not connect the 2 systems together, and a strike hits the power line,
the lightning will seek the lowest impedance �path to ground. If your
station ground is lower than the service ground, it will pass thru your
equipment to find it. Bonding the ground together eliminates this problem.
Robert KD5YVQ 





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-- 
Wes Clavey, W5WMC
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