Another question...

We have underground utilities in this neighborhood. The box on the side
of my house where the utility feed arrives has an approximately 1ft
section buried. There's actually a grade line marked on the side of the
box which I presume is a "do not exceed line. The service no doubt
enters through the bottom of this box.

I've dug carefully on one side of the box and so far haven't found a
ground rod. Before I continue digging I have a question about the
ground rod location.

Is it possible/typical that the contractor would put the ground rod
underneath the service entrance box in cases like these? If so it would
probably be pretty difficult to get to it.

Would driving another rod within a foot of the service panel be
adequate? (of course taking care not to penetrate the AC mains!)

I noticed the phone guy just put a hose clamp on the big metal
compression nut that has one side of the mains leading into the house
and put his ground under that. This is on the outside of the service
entrance box outside the house.

Would grounding through a similar compression bond to the box be a
reasonable alternative?

tnx
jtm

"Jim Miller" wrote
Another question...

We have underground utilities in this neighborhood. The box on the side
of my house where the utility feed arrives has an approximately 1ft
section buried. There's actually a grade line marked on the side of the
box which I presume is a "do not exceed line. The service no doubt
enters through the bottom of this box.

I've dug carefully on one side of the box and so far haven't found a
ground rod. Before I continue digging I have a question about the
ground rod location.

Is it possible/typical that the contractor would put the ground rod
underneath the service entrance box in cases like these? If so it would
probably be pretty difficult to get to it.

Would driving another rod within a foot of the service panel be
adequate? (of course taking care not to penetrate the AC mains!)

I noticed the phone guy just put a hose clamp on the big metal
compression nut that has one side of the mains leading into the house
and put his ground under that. This is on the outside of the service
entrance box outside the house.

Would grounding through a similar compression bond to the box be a
reasonable alternative?

tnx
jtm


Hi Jim,

The buried conduit casing of the AC mains entrance to your meter is most
likely NOT your house ground. The main AC breaker panel for your home,
whether that be in a garage or wherever (surely close to the meter though)
is where the house AC neutral wiring and house AC ground wiring all meets at
one bonding location. THAT is the source of the single point ground
conductor, which leaves your panel and finds the nearest approved earthing
connection. You may have to get under your house to see where that green
bonding jumper drops down from the panel, and penetrates the outside wall,
then connects via a bronze ground rod clamp to the home's single point
ground rod. Telephone and cable and all radio shield grounds MUST BOND to
this ground rod. It is probably just inches beneath finished grade, and
within a foot or so of your foundation wall, right outside the breaker
panel.

In the unlikely event that your builder actually used the aluminum casing of
buried conduit for his AC mains ground connection, then the telephone
company was proper in bonding to the same place. But if you have a buried
ground rod as 99% of residences do, then that is the ONLY place that all
utilities must ground to.

The reason it would be unlikely to have the conduit as a earthing ground
connection? Because the utility should inspect for a contractor installed
ground rod before they hook up. Using their buried conduit, while possibly
legal, would be unusual at best.

Hope this helps,

Jack

Hi Jack

Well I moved some stuff around in the basement and found the house
ground. It actually protrudes out of the concrete floor directly below
the two breaker panels. Each panel has what appears to be #4 solid
copper coming down to bronze clamps on this rod.

There's no ground outside at all which is why the Verizon guy chose to
ground to the Thomas and Betts meter cabinet that I mentioned which is
4ftx6"x15" or so and partially buried. Here in MD they just do direct
burial rather than use a conduit. The entry to the house panels from
the meter box is just via heavy cable, no conduit there either. The
Comcast guy just put a ground on the splitter and ran it a foot or so
to the closest circuit breaker panel.

So should I just drive one more rod pretty close to the box to finish
the daisy chain close, then go inside and bond to the single point
there? Seems crazy to take this inside... I'll have to drill a hole
through the sill plate on an angle then feed the wire up from my
proposed exterior ground rod, through the sill plate, then down the
inside of the concrete basement wall to where the other two grounds are
attached to the ground post.

tnx
jtm

"Jim Miller"
Hi Jack

Well I moved some stuff around in the basement and found the house
ground. It actually protrudes out of the concrete floor directly below
the two breaker panels. Each panel has what appears to be #4 solid
copper coming down to bronze clamps on this rod.

There's no ground outside at all which is why the Verizon guy chose to
ground to the Thomas and Betts meter cabinet that I mentioned which is
4ftx6"x15" or so and partially buried. Here in MD they just do direct
burial rather than use a conduit. The entry to the house panels from
the meter box is just via heavy cable, no conduit there either. The
Comcast guy just put a ground on the splitter and ran it a foot or so
to the closest circuit breaker panel.

So should I just drive one more rod pretty close to the box to finish
the daisy chain close, then go inside and bond to the single point
there? Seems crazy to take this inside... I'll have to drill a hole
through the sill plate on an angle then feed the wire up from my
proposed exterior ground rod, through the sill plate, then down the
inside of the concrete basement wall to where the other two grounds are
attached to the ground post.

tnx
jtm

Good job scoping out what you have, Jim. It is unfortunately, non-conformant
by your description. Utility service entrances are required to be single
point grounded at one entry point. Bonding through basement walls will never
meet that requirement, besides being difficult to accomplish.

The potential between your Verizon lines and Electric lines could be huge,
should the nearby utility pole, a tree in your yard, etc be struck. The
phone issue may never be a problem unless...you use phone-patch equipment
connected to a radio.

You previously asked if it is allright to improve the AC mains ground rod
(when you thought you had one outside). The answer is yes, and most as
installed by the building contractor are barely sufficient for handling
surge voltages that nearby lightning can send to the meter. Adding a second
and third ground rod (in a "Y" formation for instance) greatly improves the
protection from utility high voltage damage to your home, providing you have
good surge protection installed. Sans surge protection? Don't bother with
more ground rods.

In your case though, you probably have an excellent grounding electrode
under the house. You do realize that the finished grade outside is probably
as much as 10,000v "above ground" from that under-basement electrode! Too
bad Verizon didn't see fit to make their box ground at the same place. I
would ask Verizon what to do, get a grounding technician to come out to your
place and explain to him that you have communications equipment connected
and expect a code-installation of all utilities before you can complete
lightning protection systems. If he demonstrates to your satisfaction that
it DOES meet code, please sketch (paint program, or photos scanned, etc)
what you have and send it. I will be happy to get a telco communications
engineer to comment (and it won't be Verizon). It may be that the
electrical code and telco standards *do not protect you* in your individual
circumstances.

Meanwhile, you can make a bond between your AC panel ground rod and the
station single point ground, as most of us are unfortunately situated far
apart when ideally they would be next to each other. That bonding connector
can be insulated wire through interior walls, utility chases, under floors,
etc. Preferably use #6 wire minimum. It HAS to be much lower impedance that
the home's AC outlet grounding wires, how much lower is up to your
individual circumstances. I just replaced #4 copper with 13" wide 20 gage
copper sheeting, because I had over 50' of separation between station ground
and AC mains ground. That's an awful potential, and begs high voltage felt
at the station ground from a nearby strike, to blast out the back of the
radios and into the power grid. Surge protection alone cannot save you from
ground potential rise, but a bond from station ground to AC ground that is
much lower impedance than the house wiring will MINIMIZE the effect on your
equipment, and all home appliances. Richard Harrison in this group had a
much better solution for my type of problem, and that was to route ALL
antenna feedlines to the AC Mains ground point BEFORE entering the home.
Unfortunately that would have been a design issue when I started my station,
and so I used the next best alternative, the best bonding possible between
the two.

I suggest proceeding with that effort and shield grounding, etc, until an
expert from the telco and/or electric company can visit and review your
situation.

Best regards,
Jack