OK, some practical considerations then.
If I bond to the power meter on the exterior, they have what looks like a
plastic conduit running down into the ground below grade. So where do I
hook on? Drill holes and screw the strap into the box that holds the power
meter, spearing some conductive grease over everything the best way? Does
not seem a very good idea. I definitely cannot get to whatever ground rod
they may have put below grade without busting concrete.
And on the inside, I can pull the panels off and get to the mains feed
ground line. Got to be careful. Or is it enough to connect to the breaker
box casing? The connection between the casing and the "bus bar" for the
ground is not what I would call lightning nuclear duty safe.
The housebuilder should have thought ahead 7 years and asked me about it
before laying in the wires. ha ha.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Jim Brown
Sent: Tuesday, January 22, 2013 12:12 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] bonding to AC power box or inside fuse panel?
On 1/21/2013 5:10 PM, Dick Green WC1M wrote:
Some grounding decisions are not straightforward. For example, my AC and
telco services are on one side of the house and the station "single-point"
ground is on the other side of the house. It would have taken 150 feet of
low-inductance wire and at least 10 8-foot ground rods and Cadweld shots
to connect the ground systems outside the house. So I decided to bond them
together inside the house, using about 25 feet of 1/0 wire. Not the
recommended way to do it, but it my opinion a better way to ensure that
the ground systems are at the same potential.
Right. I have a similar situation with my shack. I took a "belt plus
suspenders" approach -- I ran a bare #6 around the perimeter, bonding it
to rods by the power panel, at several points around the perimeter, and
more outside the shack. Inside the shack, I have thinwall steel conduit
(EMT) between the breaker panel (entrance) and outlets under my
operating desk, which are, of course, bonded to the panel. My coax panel
is between those outlets (at floor level) and the operating desk, and
I've added a bond between the desk, the antenna panel, and the conduit.
Another example is bonding the tower ground to the single-point ground at
the house. My first tower farm is 265' from the house. Being new to tower
construction, I laid 265 feet of 1/0 ground wire in the trench running
between the two locations in order to bond the ground systems. This was
not cheap, to say the least (though it was before the big run up in copper
prices.) Later, I read an article by Polyphaser that said if the ground
systems are more than 75' apart it does no good to bond them -- the wire
inductance will be too high to make an effective connection. With this in
mind, when I installed my second tower system in a different location 220'
from the house, I did not run a separate ground wire. The Polyphaser
argument made sense to me.
Yes, it's good practice, solidly based on fundamental circuit concepts.
In fact, it's also good to add common mode ferrite chokes to the cables
running between the towers and the shack to minimize noise coupling.
73, Jim K9YC
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