"Minnie Bannister" wrote in message
...
Now that most of the snow has melted here in W. Michigan (although more
is forecast for tonight) and I have been able to get a better look at
the existing grounding arrangements, I have noticed that a heavy
stranded copper wire comes out of the ground alongside the conduit that
goes to the electricity meter; it then disappears between the slab and
the siding, so I assume that this is the ground connection to the ground
bus in the panel -- correct? If so, do I have to bring my separate
ground connection (from a radio installation, including a future antenna
tower) up into the panel, or can I simply bond it to that existing
accessible ground conductior outside the house?

Basically, yes, in this case, you should connect to the grounding system
outside the house. However if you have an overhead electric service you
should locate the antenna/tower as far away from it as you can. For a roof
mounted antenna the ground wire should go from the antenna (line of sight)
straight down to an antenna discharge unit then straight into a ground rod
driven far enough away from the house so that it is outside the roof drip
line. That ground rod should then be bonded to the main electric service
grounding electrode system using preferably, a #4 bare copper conductor.

Also, if you have an underground metal water supply line, it's very
important that you have have an unbroken (preferably #4) bare copper wire
connected from within 5 feet of where the supply line comes into the house
routed to the main electric service. Jumper across the water meter if
applicable, and jumper from the hot to cold at the water heater, if metal
pipes. Any sections of metal pipe that may have been replaced with plastic
pipe should be jumpered also. Use UL listed/approved ground
clamps/connectors, preferably bronze.

The gas meter and telephone network interface are on the opposite end
wall of the house. The first thing I noticed is that an insulated wire
that comes out of the ground alongside the gas pipe is simply twisted
around it, with the bared end just "flapping in the breeze"; there are
no marks on the pipe to suggest that the wire was ever clamped to it.

That doesn't sound good. A grounding connection should _never_ be made to
an _underground_ gas line. However, any _interior_ metal gas line should be
bonded to the main electric service grounding system. Local codes may vary.


Should I install a clamp myself, or should I call the gas company?


Completely remove any kind of grounding connections to the outside and/or
underground gas lines. To be safe you should shut down your main electric
service before working with the grounding system.


(The
telephone interface box is just a few feet away from the gas meter, but
the wire that disappears into the ground from it has a different color
insualtion from the one wrapped around the gas pipe, so I don't think
the floating wire is supposed to be the ground for the telephone.)


That doesn't sound good either. There's a possibility that the telephone
interface box is grounded to the underground gas line. You'll want to
carefully dig that wire out until you find where is goes. If you are lucky
that phone ground wire goes to a ground rod that is installed as far away
from the gas line as practical, then that ground rod should be connected to
the main electric service ground on the other side of the house, again,
preferably with a bare #4 conductor.


But one other question comes to mind: can I really believe/assume that
these existing grounds are all connected together already? Is there
really a conductor running the 60ft or more from the gas meter and
telephone interface at one end of the house to the electricity meter at
the other end?


I seriously doubt it, but there should be.


How can I be sure?

Carefully dig until you see where the wire is connected. See above.

MB

I wrote:

I understand that the NEC requires that all grounds (e.g., lightning
protection grounds and grounds for radio transmitting equipment) must be
bonded to each other and to the utility company's ground. The books I
have read say this is accomplished by connecting everything to the
ground "at the service entrance panel." But how is this to be
accomplished? By clamping the ground conductors to the conduit (after
cleaning it down to bare metal) that comes out of the ground and up to
the meter on the wall of the building? By bringing the ground conductors
through the wall of the building and into the panel and there connecting
them to the existing ground bus? Or . . . ?

The wire coming out of the meter and into the ground is probably the best
place to connect in your case. Most times the grounding connections are
made inside the main service panel on the neutral busbar and the neutral
busbar is then bonded to the panel enclosure.