Hi,

We have a nearly new home in FL (built in 2001) and I noticed recently that
our cable TV coax comes into a box on the outside of the garage before
coming into the house. I also noticed that in this box, the cable has a
grounding block attached to it, but no ground wire. So I bought some #10
copper wire and ran a wire ground wire from the grounding block in the box
down to what I thought was the grounding rod where the electrical service
and the phone were grounded. But instead it looks more like rebar instead
of a "smooth" grounding rod looks. It comes out of the ground at about a
15-30 degree angle off vertical (i.e. almost vertical).

I can see a #4 or #6 bare copper wire (which I assume is the electrical
service ground) coming out of the house and clamping to this rebar, as well
as following the grounding wire from the phone demarc box to this rod
(actually, the phone grounding wire is clamped to the electrical ground wire
about 2 inches from where the electrical ground wire clamps to the rebar. I
bought a 5/8" grounding clamp, stripped about 2 inches of insulation from my
cable TV coax ground wire, and clamped it directly to the rebar with the
rest of them.

Then, I noticed about 16 inches away was what looked like a regular
grounding rod sticking out of the ground about 2 inches. This rod is
smoother and does not appear to be rebar, but more of a regular grounding
rod (or at least what I thought a regular grounding rod looked like). Both
the rebar and the grounding rod are less than 6 feet from the AC service
panel in the garage. I dug down about 6 inches, but couldn't find anything
attached to this smooth grounding rod.

So my questions a
(a) Why is everything grounded to the rebar when there's a grounding rod
right next to it?
(b) Should the rod and the rebar be bonded together somehow?
(c) I can't determine if the rebar is part of the foundation rebar or a
piece of rebar driven straight down into the ground. Is it ok as the
house's ground if it's part of the foundation rebar and not an 8' stake
going down into the ground?

Thanks in advance!
-- Vinnie

It's because everyone working on your house was an idiot.

Sorry for the sarcasm but the same people were working on my house.
Example, screened doors installed upside down. Missing flashing,
french drain full of concrete (no joke).

The rebar was probably put in by mistake and everyone thought it was
the grounding rod before it got super rusty.



"Vinnie Murdico" wrote
in message . net...
Hi,

We have a nearly new home in FL (built in 2001) and I noticed
recently that
our cable TV coax comes into a box on the outside of the garage
before
coming into the house. I also noticed that in this box, the cable
has a
grounding block attached to it, but no ground wire. So I bought
some #10
copper wire and ran a wire ground wire from the grounding block in
the box
down to what I thought was the grounding rod where the electrical
service
and the phone were grounded. But instead it looks more like rebar
instead
of a "smooth" grounding rod looks. It comes out of the ground at
about a
15-30 degree angle off vertical (i.e. almost vertical).

I can see a #4 or #6 bare copper wire (which I assume is the
electrical
service ground) coming out of the house and clamping to this rebar,
as well
as following the grounding wire from the phone demarc box to this
rod
(actually, the phone grounding wire is clamped to the electrical
ground wire
about 2 inches from where the electrical ground wire clamps to the
rebar. I
bought a 5/8" grounding clamp, stripped about 2 inches of insulation
from my
cable TV coax ground wire, and clamped it directly to the rebar with
the
rest of them.

Then, I noticed about 16 inches away was what looked like a regular
grounding rod sticking out of the ground about 2 inches. This rod
is
smoother and does not appear to be rebar, but more of a regular
grounding
rod (or at least what I thought a regular grounding rod looked
like). Both
the rebar and the grounding rod are less than 6 feet from the AC
service
panel in the garage. I dug down about 6 inches, but couldn't find
anything
attached to this smooth grounding rod.

So my questions a
(a) Why is everything grounded to the rebar when there's a grounding
rod
right next to it?
(b) Should the rod and the rebar be bonded together somehow?
(c) I can't determine if the rebar is part of the foundation rebar
or a
piece of rebar driven straight down into the ground. Is it ok as
the
house's ground if it's part of the foundation rebar and not an 8'
stake
going down into the ground?

Thanks in advance!
-- Vinnie

John Gilmer wrote:
Before you complete the bonding connection, check the resistance between
your "proper" ground and your re-bar. If you have time on your hands,
drive a second "proper" ground rod (two "proper" grounds rods will meet NEC
requirements) and measure the various resistances. You may find that the
re-bar is a better ground than the "proper" ground.

Measure the (AC) voltage difference before you measure the resistance. If it's
not zero, don't measure the resistance. Two ground rods some distance apart typically
have a voltage difference between them even if not attached to anything, but especially
if one is in use and the other isn't.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

"Ron Hardin" wrote in message
...
John Gilmer wrote:
Before you complete the bonding connection, check the resistance between
your "proper" ground and your re-bar. If you have time on your hands,
drive a second "proper" ground rod (two "proper" grounds rods will meet
NEC
requirements) and measure the various resistances. You may find that
the
re-bar is a better ground than the "proper" ground.

Measure the (AC) voltage difference before you measure the resistance. If
it's
not zero, don't measure the resistance. Two ground rods some distance
apart typically
have a voltage difference between them even if not attached to anything,
but especially
if one is in use and the other isn't.

Well, with a high input impedance voltmeter (like your typical digital
model) it would be unusualy to NOT detect a fraction of a volt difference.

If such things make you nervous, "load" the circuit by putting a 1000 ohm
resistor across the DVM input leads for all measurements. The resistor
should provide enough "load" to significantly reduce the voltage reading to
your comform level. If you have some stray current leakage inside your
house, pull the main breaker during your testing.

The 1000 ohm resistor will change your resistance measurements but your
expected value should be less that 100 ohms (much less with "good" grounds).

But checking the voltage before measuring resistance is, indeed, a good
practice.