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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